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HomeMy WebLinkAbout01052018_NOI_Expanded Project_Sconset_Submittal (1)Submitted to: Nantucket Conservation Commission 2 Bathing Beach Road Nantucket, Massachusetts 02554 Submitted by: Siasconset Beach Preservation Fund P.O. Box 2279 Nantucket, Massachusetts 02554 January 5, 2018 Notice of Intent (M.G.L. c. 131, §40) and Town of Nantucket Wetlands Bylaw Chapter 136 Prepared by: Epsilon Associates, Inc. 3 Mill & Main Place, Suite 250 Maynard, Massachusetts 01754 In Association with: W.F. Baird & Associates Ltd. 5014 NW 24th Circle Boca Raton, FL 33431 Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project PRINCIPALS Theodore A Barten, PE Margaret B Briggs Michael E Guski, CCM Dale T Raczynski, PE Cindy Schlessinger Lester B Smith, Jr Robert D O’Neal, CCM, INCE Andrew D Magee Michael D Howard, PWS Douglas J Kelleher AJ Jablonowski, PE Stephen H Slocomb, PE David E Hewett, LEED AP Dwight R Dunk, LPD David C. Klinch, PWS, PMP Samuel G. Mygatt, LLB 1943-2010 ASSOCIATES Richard M. Lampeter, INCE Maria B. Hartnett Geoffrey Starsiak 3 Mill & Main Place, Suite 250 Maynard, MA 01754 www.epsilonassociates.com January 5, 2018 Mr. Jeff Carlson Natural Resources Director, Town of Nantucket Conservation Commission Office 2 Bathing Beach Road Nantucket, MA 02554 Subject: Application for Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Dear Mr. Carlson: We are now entering the fifth winter storm season for the erosion protection system that was installed along Baxter Road in 2013-14. As agreed to by SBPF, the Town of Nantucket, and the Conservation Commission, the permitting to expand this erosion protection has been on hold until 2018 to allow time for it to be observed and studied. Since that time period has expired, Epsilon Associates has been engaged to prepare a Notice of Intent to expand the system to protect the area where there is a currently eroding bluff, which would extend north to 119 Baxter Road and south to 59 Baxter Road (plus returns). The NOI also proposes consideration of updates to the design, monitoring, and mitigation based on the information collected to date. The project is described in detail in the attached NOI. Please note that the original abutters list and labels will be provided separately by counsel. The project is proposed to be on the above private lots, as well as a portion of the so- called Flagg lots, which are owned by the Town of Nantucket. SBPF is in the process of collecting the assents from the property owners needed for this filing, and anticipates appearing before the Board of Selectmen on January 17, 2018 to affirm the Town’s standing assent to these filings. Due to the high level of public interest in this project in the past, the complexity of this matter, and the likely need for technical review of this matter, we request that you accept this filing as-is and that you post it on the Conservation Commission website so that the applicable information is publicly available as soon as possible. We also request that you begin the process of engaging a technical consultant for the Commission, as that process itself has proven complicated. Please contact me, or Attorney Steven Cohen, with any questions about the filing. Mr. Jeff Carlson 2 Nantucket Conservation Commission January 5, 2018 Please confirm that you will be noticing this matter for the January 24, 2018 Conservation Commission hearing, so that we can make arrangements accordingly. Sincerely, EPSILON ASSOCIATES, INC. Maria B. Hartnett Associate Notice of Intent Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, Massachusetts Submitted to: NANTUCKET CONSERVATION COMMISSION 2 Bathing Beach Road Nantucket, Massachusetts 02554 Submitted by: SIASCONSET BEACH PRESERVATION FUND PO Box 2279 Nantucket, MA 02554 Prepared by: EPSILON ASSOCIATES, INC. 3 Mill & Main Place, Suite 250 Maynard, MA 01754 In Association with: W.F. BAIRD & ASSOCIATES LTD. 5014 NW 24th Circle Boca Raton, FL 33431 January 5, 2018 Table of Contents 21597/Lighthouse/NOI i Table of Contents Epsilon Associates, Inc. TABLE OF CONTENTS 1.0 INTRODUCTION 1-1 1.1 Project Background 1-1 1.2 Summary of Proposed Project 1-2 2.0 EXISTING CONDITIONS 2-1 2.1 Houses and Public Infrastructure in the Project Area 2-1 2.2 Wetland Resources at the Site 2-2 2.3 Updated Bank Contribution Volume 2-3 3.0 PROJECT DESCRIPTION 3-1 3.1 Geotextile Tubes 3-1 3.1.1 Overview 3-1 3.1.2 Design Basis 3-1 3.2 Vegetation 3-2 3.3 Sand Source 3-3 3.4 Construction Overview 3-3 3.5 Alternatives 3-5 3.6 Wetland Resource Area Impacts 3-7 4.0 MONITORING AND MITIGATION 4-1 4.1 Monitoring 4-1 4.2 Mitigation 4-2 4.3 Failure Criteria 4-3 5.0 REGULATORY CONSISTENCY 5-1 5.1 Compliance with State Wetlands Regulations 5-1 5.2 Compliance with Local Wetlands Regulations 5-6 5.3 Waiver Request 5-14 List of Attachments Attachment B Figures Attachment C Project Plans Attachment D Construction Dates of Baxter Road Properties Attachment E Annual Review – Sconset Geotextile Tube Project (SE48-2824) (dated December 13, 2016) Attachment F Response to Comments on Annual Report (dated May 2, 2017) Attachment G Baxter Road Geotube Project – Coastal Bank Retreat Calculations Attachment H Bank Swallow Survey Results and Habitat Requirements (dated July 3, 2017) Attachment I Sconset Bluff Erosion Control Alternatives and Recommendations (dated July 2013) 21597/Lighthouse/NOI ii Table of Contents Epsilon Associates, Inc. List of Attachments (Continued) Attachment J Milone & MacBroom Letter with Alternatives Analysis (dated October 25, 2013) Attachment K Supplemental Information for Notice of Intent (dated March 14, 2014) Attachment L Alternatives Analysis for the (1) Fourth Tier of the Existing Three Tier Geotextile Tube Structures and the (2) Return Design (dated October 23, 2014) Attachment M DEP Superseding Order of Conditions (dated December 19, 2014) Attachment N Final Order of Conditions (SE48-2824) (dated September 30, 2015) Attachment O Memorandum of Understanding (MOU) Between the Town of Nantucket and SBPF (dated July 5, 2013) and Amendment to the MOU (dated October 9, 2013) Attachment P Emergency Status for Homes and Public Infrastructure Along Baxter Road, Nantucket, MA (dated November 25, 2013) Attachment Q Property Ownership and Abutter Information Attachment R Filing Fee Information List of Figures Figure 1 USGS Locus Figure 2 Aerial Locus Figure 3 August 2017 Existing Conditions South of Lot 61 Figure 4 August 2017 Existing Conditions Lots 59 to 65 Figure 5 August 2017 Existing Conditions Lots 63 to 79 Figure 6 August 2017 Existing Conditions Lots 73 Northward Figure 7 August 2017 Existing Conditions Lots 85 to 105 Figure 8 August 2017 Existing Conditions Lots 93 to 115 Figure 9 Pre-1978 House Status Figure 10 Wetland Resource Areas Figure 11 FEMA Q3 Flood Zones Figure 12 August 2017 Existing Conditions – Coastal Dune and Coastal Bank Figure 13 NHESP Habitat Map Figure 14 June 2017 Image of Vegetation in Existing Geotextile Tube Project Area Figure 15 Shoreline Monitoring Survey Transects – Wauwinet to Sewer Beds Figure 16 Shoreline Monitoring Survey Transects – Project Area 21597/Lighthouse/NOI iii Table of Contents Epsilon Associates, Inc. List of Tables Table 2-1 Average Bank Retreat Rates, 107-119 Baxter Rd and 71-85 Baxter Rd Table 2-2 Detailed Analysis of Bank Retreat from 1994-2017 at 107-119 Baxter Rd Table 2-3 Detailed Analysis of Bank Retreat from 2003-2017 at 85-71 Baxter Rd Table 2-3 Detailed Analysis of Bank Retreat from 2003-2017 at 85-71 Baxter Rd (Continued) Table 2-4 Bank Height 59-85 Baxter Road and 107-119 Baxter Road Table 2-5 Standard Calculation of Compensatory Mitigation for 59-85 Baxter Road and 107-119 Baxter Road Table 3-1 Wetland Resource Impacts WPA Form 3 Notice of Intent wpaform3.doc • rev. 6/28/2016 Page 1 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town Important: When filling out forms on the computer, use only the tab key to move your cursor - do not use the return key. Note: Before completing this form consult your local Conservation Commission regarding any municipal bylaw or ordinance. A. General Information 1. Project Location (Note: electronic filers will click on button to locate project site): 59-119 Baxter Road (plus returns) a. Street Address Nantucket b. City/Town 02554 c. Zip Code Latitude and Longitude: d. Latitude e. Longitude f. Assessors Map/Plat Number g. Parcel /Lot Number 2. Applicant: Josh a. First Name Posner b. Last Name Siasconset Beach Preservation Fund (SBPF) c. Organization P.O. Box 2279 d. Street Address Nantucket e. City/Town MA f. State 02584 g. Zip Code h. Phone Number i. Fax Number jposner@risingtidellc.net j. Email Address 3. Property owner (required if different from applicant): Check if more than one owner a. First Name b. Last Name c. Organization See attached property owners (Town of Nantucket and property owners 59 -119 Baxter Road) d. Street Address e. City/Town f. State g. Zip Code h. Phone Number i. Fax Number j. Email address 4. Representative (if any): Maria a. First Name Hartnett b. Last Name Epsilon Associates, Inc. c. Company 3 Mill & Main Place, Suite 250 d. Street Address Maynard e. City/Town MA f. State 01754 g. Zip Code 410-451-9766 h. Phone Number 978-897-0099 i. Fax Number mhartnett@epsilonassociates.com j. Email address 5. Total WPA Fee Paid (from NOI Wetland Fee Transmittal Form): a. Total Fee Paid b. State Fee Paid c. City/Town Fee Paid wpaform3.doc • rev. 6/28/2016 Page 2 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town A. General Information (continued) 6. General Project Description: Expansion of the existing geotextile tube project to provide storm damage protection for homes and public infrastructure along the length of Sconset bluff that is eroding. The new section of geotextile tubes will extend north from the Existing Project to 119 Baxter Rd and south from the Existing Project to 59 Baxter Rd (plus returns), providing continuous protection from 59 to 119 Baxter Road. 7a. Project Type Checklist: (Limited Project Types see Section A. 7b.) 1. Single Family Home 2. Residential Subdivision 3. Commercial/Industrial 4. Dock/Pier 5. Utilities 6. Coastal engineering Structure 7. Agriculture (e.g., cranberries, forestry) 8. Transportation 9. Other 7b. Is any portion of the proposed activity eligible to be treated as a limited project (including Ecological Restoration Limited Project) subject to 310 CMR 10.24 (coastal) or 310 CMR 10.53 (inland)? 1. Yes No If yes, describe which limited project applies to this project. (See 310 CMR 10.24 and 10.53 for a complete list and description of limited project types) 2. Limited Project Type If the proposed activity is eligible to be treated as an Ecological Restoration Limited Project (310 CMR10.24(8), 310 CMR 10.53(4)), complete and attach Appendix A: Ecological Restoration Limited Project Checklist and Signed Certification. 8. Property recorded at the Registry of Deeds for: Nantucket a. County b. Certificate # (if registered land) See Attachment Q c. Book See Attachment Q d. Page Number B. Buffer Zone & Resource Area Impacts (temporary & permanent) 1. Buffer Zone Only – Check if the project is located only in the Buffer Zone of a Bordering Vegetated Wetland, Inland Bank, or Coastal Resource Area. 2. Inland Resource Areas (see 310 CMR 10.54-10.58; if not applicable, go to Section B.3, Coastal Resource Areas). Check all that apply below. Attach narrative and any supporting documentation describing how the project will meet all performance standards for each of the resource areas altered, including standards requiring consideration of alternative project design or location. wpaform3.doc • rev. 6/28/2016 Page 3 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town B. Buffer Zone & Resource Area Impacts (temporary & permanent) (cont’d) For all projects affecting other Resource Areas, please attach a narrative explaining how the resource area was delineated. Resource Area Size of Proposed Alteration Proposed Replacement (if any) a. Bank 1. linear feet 2. linear feet b. Bordering Vegetated Wetland 1. square feet 2. square feet c. Land Under Waterbodies and Waterways 1. square feet 2. square feet 3. cubic yards dredged Resource Area Size of Proposed Alteration Proposed Replacement (if any) d. Bordering Land Subject to Flooding 1. square feet 2. square feet 3. cubic feet of flood storage lost 4. cubic feet replaced e. Isolated Land Subject to Flooding 1. square feet 2. cubic feet of flood storage lost 3. cubic feet replaced f. Riverfront Area 1. Name of Waterway (if available) - specify coastal or inland 2. Width of Riverfront Area (check one): 25 ft. - Designated Densely Developed Areas only 100 ft. - New agricultural projects only 200 ft. - All other projects 3. Total area of Riverfront Area on the site of the proposed project: square feet 4. Proposed alteration of the Riverfront Area: a. total square feet b. square feet within 100 ft. c. square feet between 100 ft. and 200 ft. 5. Has an alternatives analysis been done and is it attached to this NOI? Yes No 6. Was the lot where the activity is proposed created prior to August 1, 1996? Yes No 3. Coastal Resource Areas: (See 310 CMR 10.25-10.35) Note: for coastal riverfront areas, please complete Section B.2.f. above. wpaform3.doc • rev. 6/28/2016 Page 4 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town B. Buffer Zone & Resource Area Impacts (temporary & permanent) (cont’d) Check all that apply below. Attach narrative and supporting documentation describing how the project will meet all performance standards for each of the resource areas altered, including standards requiring consideration of alternative project design or location. Online Users: Include your document transaction number (provided on your receipt page) with all supplementary information you submit to the Department. Resource Area Size of Proposed Alteration Proposed Replacement (if any) a. Designated Port Areas Indicate size under Land Under the Ocean, below b. Land Under the Ocean 1. square feet 2. cubic yards dredged c. Barrier Beach Indicate size under Coastal Beaches and/or Coastal Dunes below d. Coastal Beaches 67,000 SF geotube/ 105,000 SF temporary trench 2. cubic yards beach nourishment e. Coastal Dunes 1. square feet 2. cubic yards dune nourishment Size of Proposed Alteration Proposed Replacement (if any) f. Coastal Banks 2,873 1. linear feet g. Rocky Intertidal Shores 1. square feet h. Salt Marshes 1. square feet 2. sq ft restoration, rehab., creation i. Land Under Salt Ponds 1. square feet 2. cubic yards dredged j. Land Containing Shellfish 1. square feet k. Fish Runs Indicate size under Coastal Banks, inland Bank, Land Under the Ocean, and/or inland Land Under Waterbodies and Waterways, above 1. cubic yards dredged l. Land Subject to Coastal Storm Flowage 335 1. square feet 4. Restoration/Enhancement If the project is for the purpose of restoring or enhancing a wetland resource area in addition to the square footage that has been entered in Section B.2.b or B.3.h above, please enter the additional amount here. a. square feet of BVW b. square feet of Salt Marsh 5. Project Involves Stream Crossings a. number of new stream crossings b. number of replacement stream crossings wpaform3.doc • rev. 6/28/2016 Page 5 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town C. Other Applicable Standards and Requirements This is a proposal for an Ecological Restoration Limited Project. Skip Section C and complete Appendix A: Ecological Restoration Limited Project Checklists – Required Actions (310 CMR 10.11). Streamlined Massachusetts Endangered Species Act/Wetlands Protection Act Review 1. Is any portion of the proposed project located in Estimated Habitat of Rare Wildlife as indicated on the most recent Estimated Habitat Map of State-Listed Rare Wetland Wildlife published by the Natural Heritage and Endangered Species Program (NHESP)? To view habitat maps, see the Massachusetts Natural Heritage Atlas or go to http://maps.massgis.state.ma.us/PRI_EST_HAB/viewer.htm. a. Yes No If yes, include proof of mailing or hand delivery of NOI to: Natural Heritage and Endangered Species Program Division of Fisheries and Wildlife 1 Rabbit Hill Road Westborough, MA 01581 August 1, 2017 b. Date of map If yes, the project is also subject to Massachusetts Endangered Species Act (MESA) review (321 CMR 10.18). To qualify for a streamlined, 30-day, MESA/Wetlands Protection Act review, please complete Section C.1.c, and include requested materials with this Notice of Intent (NOI); OR complete Section C.2.f, if applicable. If MESA supplemental information is not included with the NOI, by completing Section 1 of this form, the NHESP will require a separate MESA filing which may take up to 90 days to review (unless noted exceptions in Section 2 apply, see below). c. Submit Supplemental Information for Endangered Species Review∗ 1. Percentage/acreage of property to be altered: (a) within wetland Resource Area percentage/acreage (b) outside Resource Area percentage/acreage 2. Assessor’s Map or right-of-way plan of site 2. Project plans for entire project site, including wetland resource areas and areas outside of wetlands jurisdiction, showing existing and proposed conditions, existing and proposed tree/vegetation clearing line, and clearly demarcated limits of work ∗∗ (a) Project description (including description of impacts outside of wetland resource area & buffer zone) (b) Photographs representative of the site ∗ Some projects not in Estimated Habitat may be located in Priority Habitat, and require NHESP review (see http://www.mass.gov/eea/agencies/dfg/dfw/natural-heritage/regulatory-review/). Priority Habitat includes habitat for state-listed plants and strictly upland species not protected by the Wetlands Protection Act. ∗∗ MESA projects may not be segmented (321 CMR 10.16). The applicant must disclose full development plans even if such plans are not required as part of the Notice of Intent process. wpaform3.doc • rev. 6/28/2016 Page 6 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town C. Other Applicable Standards and Requirements (cont’d) (c) MESA filing fee (fee information available at http://www.mass.gov/dfwele/dfw/nhesp/regulatory_review/mesa/mesa_fee_schedule.htm). Make check payable to “Commonwealth of Massachusetts - NHESP” and mail to NHESP at above address Projects altering 10 or more acres of land, also submit: (d) Vegetation cover type map of site (e) Project plans showing Priority & Estimated Habitat boundaries (f) OR Check One of the Following 1. Project is exempt from MESA review. Attach applicant letter indicating which MESA exemption applies. (See 321 CMR 10.14, http://www.mass.gov/dfwele/dfw/nhesp/regulatory_review/mesa/mesa_exemptions.htm; the NOI must still be sent to NHESP if the project is within estimated habitat pursuant to 310 CMR 10.37 and 10.59.) 2. Separate MESA review ongoing. a. NHESP Tracking # b. Date submitted to NHESP 3. Separate MESA review completed. Include copy of NHESP “no Take” determination or valid Conservation & Management Permit with approved plan. 3. For coastal projects only, is any portion of the proposed project located below the mean high water line or in a fish run? a. Not applicable – project is in inland resource area only b. Yes No If yes, include proof of mailing, hand delivery, or electronic delivery of NOI to either: South Shore - Cohasset to Rhode Island border, and the Cape & Islands: Division of Marine Fisheries - Southeast Marine Fisheries Station Attn: Environmental Reviewer 1213 Purchase Street – 3rd Floor New Bedford, MA 02740-6694 Email: DMF.EnvReview-South@state.ma.us North Shore - Hull to New Hampshire border: Division of Marine Fisheries - North Shore Office Attn: Environmental Reviewer 30 Emerson Avenue Gloucester, MA 01930 Email: DMF.EnvReview-North@state.ma.us Also if yes, the project may require a Chapter 91 license. For coastal towns in the Northeast Region, please contact MassDEP’s Boston Office. For coastal towns in the Southeast Region, please contact MassDEP’s Southeast Regional Office. wpaform3.doc • rev. 6/28/2016 Page 7 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town C. Other Applicable Standards and Requirements (cont’d) Online Users: Include your document transaction number (provided on your receipt page) with all supplementary information you submit to the Department. 4. Is any portion of the proposed project within an Area of Critical Environmental Concern (ACEC)? a. Yes No If yes, provide name of ACEC (see instructions to WPA Form 3 or MassDEP Website for ACEC locations). Note: electronic filers click on Website. b. ACEC 5. Is any portion of the proposed project within an area designated as an Outstanding Resource Water (ORW) as designated in the Massachusetts Surface Water Quality Standards, 314 CMR 4.00? a. Yes No 6. Is any portion of the site subject to a Wetlands Restriction Order under the Inland Wetlands Restriction Act (M.G.L. c. 131, § 40A) or the Coastal Wetlands Restriction Act (M.G.L. c. 130, § 105)? a. Yes No 7. Is this project subject to provisions of the MassDEP Stormwater Management Standards? a. Yes. Attach a copy of the Stormwater Report as required by the Stormwater Management Standards per 310 CMR 10.05(6)(k)-(q) and check if: 1. Applying for Low Impact Development (LID) site design credits (as described in Stormwater Management Handbook Vol. 2, Chapter 3) 2. A portion of the site constitutes redevelopment 3. Proprietary BMPs are included in the Stormwater Management System. b. No. Check why the project is exempt: 1. Single-family house 2. Emergency road repair 3. Small Residential Subdivision (less than or equal to 4 single-family houses or less than or equal to 4 units in multi-family housing project) with no discharge to Critical Areas. D. Additional Information This is a proposal for an Ecological Restoration Limited Project. Skip Section D and complete Appendix A: Ecological Restoration Notice of Intent – Minimum Required Documents (310 CMR 10.12). Applicants must include the following with this Notice of Intent (NOI). See instructions for details. Online Users: Attach the document transaction number (provided on your receipt page) for any of the following information you submit to the Department. 1. USGS or other map of the area (along with a narrative description, if necessary) containing sufficient information for the Conservation Commission and the Department to locate the site. (Electronic filers may omit this item.) 2. Plans identifying the location of proposed activities (including activities proposed to serve as a Bordering Vegetated Wetland [BVW] replication area or other mitigating measure) relative to the boundaries of each affected resource area. wpaform3.doc • rev. 6/28/2016 Page 8 of 9 4 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands WPA Form 3 – Notice of Intent Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Provided by MassDEP: MassDEP File Number Document Transaction Number Nantucket City/Town D. Additional Information (cont’d) 3. Identify the method for BVW and other resource area boundary delineations (MassDEP BVW Field Data Form(s), Determination of Applicability, Order of Resource Area Delineation, etc.), and attach documentation of the methodology. 4. List the titles and dates for all plans and other materials submitted with this NOI. See Attachment C a. Plan Title b. Prepared By c. Signed and Stamped by d. Final Revision Date e. Scale f. Additional Plan or Document Title g. Date 5. If there is more than one property owner, please attach a list of these property owners not listed on this form. 6. Attach proof of mailing for Natural Heritage and Endangered Species Program, if needed. 7. Attach proof of mailing for Massachusetts Division of Marine Fisheries, if needed. 8. Attach NOI Wetland Fee Transmittal Form 9. Attach Stormwater Report, if needed. E. Fees 1. Fee Exempt: No filing fee shall be assessed for projects of any city, town, county, or district of the Commonwealth, federally recognized Indian tribe housing authority, municipal housing authority, or the Massachusetts Bay Transportation Authority. Applicants must submit the following information (in addition to pages 1 and 2 of the NOI Wetland Fee Transmittal Form) to confirm fee payment: 35972 2. Municipal Check Number 1/3/2018 3. Check date 35971 4. State Check Number 1/3/2018 5. Check date Epsilon Associates 6. Payor name on check: First Name 7. Payor name on check: Last Name 1/3/18 Attachment A Project Narrative 21597/Lighthouse/NOI 1-1 Introduction Epsilon Associates, Inc. 1.0 INTRODUCTION On behalf of the Siasconset Beach Preservation Fund, Inc. (SBPF) (the Applicant), and with consent of the land owners, including the Town of Nantucket, Epsilon Associates, Inc. (Epsilon) is submitting this Notice of Intent (NOI) to the Nantucket Conservation Commission (NCC) for the Baxter Road and Sconset Bluff Storm Damage Prevention Project. This NOI has been prepared in accordance with the Massachusetts Wetlands Protection Act (WPA) (M.G.L. c. 131, § 40) and its implementing Regulations (310 CMR 10.00) (state wetlands regulations), Chapter 136 of the Nantucket Wetland Protection Bylaw (Bylaw), and the local regulations adopted to implement the Bylaw (local wetlands regulations). 1.1 Project Background The SBPF currently holds an Order of Conditions (File No. SE48-2824) for the Baxter Road and Sconset Bluff Stabilization Project (the “Existing Project”). During the winter storms of 2012-2013, significant retreat (up to 20 to 30 feet or more) of Sconset Bluff occurred, leaving the top of the bluff as close as 30 to 40 feet to edge of Baxter Road in several areas, with many homes less than 25 feet from the top of the bluff. The Town of Nantucket (the “Town”) and SBPF entered into a Memorandum of Understanding to support permitting of a 4000 foot- long rock revetment at the toe of the bluff running from near the Lighthouse property to mid- Baxter, and a NOI was filed with the NCC in July 2013. As the 2013-2014 winter storm season approached and the revetment NOI was still pending, SBPF and the Town jointly filed another NOI for 1,500 feet of geotextile tubes in October 2013. In November and December, several emergency certification applications were filed with the NCC and also to the state Department of Environmental Protection (DEP) on appeal, and ultimately the NCC approved an Emergency Certification request jointly filed by the Town and SBPF for 900-feet of three tiers of geotextile tubes. A subsequent Order of Conditions issued by the NCC in September 2015 permitted the installation of returns and a fourth tier in certain locations. The Existing Project consists of a combination of three and four tiers of geotextile tubes, vegetation planting on the bluff face, and the installation of stormwater runoff drainage system (Figures 1 and 2). The Project was constructed in two phases by the SBPF. The first phase was constructed in late December 2013 and January 2014 under an Emergency Certification approval issued by the NCC. The first phase consisted of the installation of three stacked tiers of 45-foot circumference geotextile tubes at the base of the eroding Sconset Bluff. The first phase of geotextile tubes extended along approximately 852 feet at the toe of the bluff from 87-105 Baxter Road. The second phase was constructed in October 2015 through February 2016 and included the installation of a fourth tier of geotextile tubes on Lots 91-99, intermediate returns, end returns, and a surface runoff drainage system. With the returns included, the total length of the Existing Project is now 947 feet. 21597/Lighthouse/NOI 1-2 Introduction Epsilon Associates, Inc. 1.2 Summary of Proposed Project The Applicant is proposing to extend the existing geotextile tube project to provide storm damage protection for homes and other public infrastructure along the portion of the Sconset Bluff that continues to actively erode. The new section of geotextile tubes will extend north from the Existing Project to 119 Baxter Road and south from the Existing Project to 59 Baxter Road (plus returns), thereby providing continuous protection from 591 to 119 Baxter Road (see Figures 1 and 2). The length of the Proposed Project is 895 feet to the north of the Existing Project (821 feet plus 74 feet of returns) and 1,978 feet to the south of the Existing Project (1,909 feet plus 69 feet of returns), for a total new length of 2,873 feet. In order to provide protection from a 100 to 200-year storm, four tiers of geotextile tubes are proposed. These four tiers of geotextile tubes will provide continuous protection for the entire length of Sconset Bluff that is vulnerable to erosion and storm damage. As with the Existing Project, the bluff face will be vegetated using American beachgrass or other native vegetation where needed to help stabilize the face of the bluff and prevent surface erosion. A similar sand mitigation program is proposed as for the Existing Project. Collectively, the new geotextile tubes, proposed bluff vegetation, and sand mitigation are referred to as the “Proposed Project.” The Proposed Project will incorporate a robust monitoring program that is similar to what has been implemented for the Existing Project and will adopt the same failure criteria as are currently required for the Existing Project. 1 The segments of the Project at 59 Baxter and the southern half of 61 Baxter will not be built until erosion removes the existing small coastal dune. 21597/Lighthouse/NOI 2-1 Existing Conditions Epsilon Associates, Inc. 2.0 EXISTING CONDITIONS The Project area is located on private and Town-owned land along ‘Sconset Bluff on the eastern shore of Nantucket Island. ‘Sconset Bluff is a steep, actively-eroding coastal bank (and will be referred to hereafter as the “bank”) fronted by a steep, medium to coarse-grained coastal beach. Throughout most of the Project area, this coastal bank exhibits evidence of erosion primarily as a result of storm waves eroding the toe of the bank (Figures 3-8). As shown on Figure 3, erosion has progressed as far south as 61 Baxter Road. A number of residential buildings (private homes) along the eastern side of Baxter Road lie immediately landward of the top of the eroding coastal bank. Likewise, public infrastructure is threatened by bank erosion including Baxter Road, which is a public way and the only point of access to the historic Sankaty Lighthouse, as well as access for the public, residents, and emergency vehicles to more than 100 homes. Various utilities (water, sewer, communication and electric services) are also contained within the Baxter Road right-of-way. The bank also includes a public access way and Town land at the base that is being lost as the bank recedes. The public access way is the ‘Sconset Foot-path, informally known as the Bluff Walk, which historically existed from Sconset Village to the Lighthouse (and likely even extending as far north as Sesachacha Pond prior to erection of the Lighthouse in 1849)2. Those portions of the Bluff Walk located north of 69 Baxter Road have been lost to ongoing erosion, and a “Closed” sign has been placed at 69 Baxter Road to indicate the end of the Bluff Walk. 2.1 Houses and Public Infrastructure in the Project Area The Project area includes multiple historic homes, as detailed in Table 1 of Attachment D. Many of the threatened homes have significant historical value3 and, as such, form the core of a culturally and architecturally important historic community. They also represent a significant financial contribution to the Town of Nantucket via taxes paid. Were they to be lost, taxes on the remainder of Nantucket’s taxpayers would have to be raised accordingly. Figure 9 shows which homes were built prior to 1978 and is based on the information in Table 1 in Attachment D. Most of the homes on the landward and seaward sides of Baxter Road were built prior to 1978, though there are now some vacant lots where homes have been moved off the lot due to erosion. Specific to the Proposed Project: 2 “ Report of the Sconset Foot-path Public Access Subcommittee of the Roads and Rights of Way Committee,” 2010, page 14. 3 Nantucket Preservation Trust. 2007. ‘Sconset Historic Site Survey. 21597/Lighthouse/NOI 2-2 Existing Conditions Epsilon Associates, Inc. Northern Segment of Project (107-119 Baxter Road) ♦ Lots 107 and 107A (along with the northern portion of Lot 105) are vacant; however, protection across these lots is required in order to avoid detrimental gaps when connecting the geotextile tubes from the Existing Project at 105 Baxter Road to the pre-1978 houses at 109-115 Baxter Road. Adding geotextile tubes at these lots also provides protection for the vital infrastructure (Baxter Road and associated utilities) that provide access and critical services for pre-1978 homes. ♦ Lots 109, 113, and 115 contain pre-1978 houses. ♦ Lot 117 is currently vacant but previously included a pre-1978 home that was moved across the street to 116 Baxter. Protection at this lot is necessary to provide protection for the pre-1978 home on the landward side of Baxter Road, to provide adequate protection to the adjacent pre-1978 homes, and to provide protection for the vital infrastructure (Baxter Road and associated utilizes) that provide access and critical services for pre-1978 homes. ♦ Lot 119 is currently vacant; protection is needed at this lot to install the end of the system and provide an adequate level of storm damage protection to the adjacent pre- 1978 homes. Southern Segment of Project (59-85 Baxter Road) ♦ Lots 59 through 83 contain pre-1978 houses, totaling 13 houses. ♦ Lot 85 (along with the southern portion of Lot 87) is a vacant lot that previously included a pre-1978 house. Protection across this lot is required in order to avoid detrimental gaps when connecting the geotextile tubes from the Existing Project at 87 Baxter Road to the pre-1978 houses at 61-83 Baxter Road, to provide protection for the pre-1978 home on the landward side of Baxter Road, and to provide protection for the vital infrastructure (Baxter Road and associated utilizes) that provide access and critical services for pre-1978 homes. Public Infrastructure Public infrastructure at the site includes Baxter Road itself, along with associated water, sewer, communication, and electric service lines located within the right-of-way. 2.2 Wetland Resources at the Site Work associated with the Project will be located in the following coastal wetland resource areas subject to the jurisdiction of the NCC under the WPA, local Bylaw, and the respective state wetlands regulations and local wetlands regulations: 21597/Lighthouse/NOI 2-3 Existing Conditions Epsilon Associates, Inc. ♦ Coastal Bank (see Figure 10); ♦ Coastal Beach (see Figure 10); and ♦ Land Subject to Coastal Storm Flowage (LSCSF) (see Figure 11). A very narrow coastal dune, fronting the coastal bank, is present starting at the stairway at 61 Baxter Road and extending southward (Figure 12). The segments of the Project at 59 Baxter and the southern half of 61 Baxter will not be built until erosion removes the existing small coastal dune. The Natural Heritage and Endangered Species Program (NHESP) Estimated and Priority Habitat of Rare and Endangered Species Map (Figure 13) shows priority habitats for State- protected species and Estimated Habitats for rare wildlife from Lot 61 southward. Presumably this mapped area is for Piping Plovers (a State and Federally-listed “Threatened” species) and Least Terns (a State-listed species of “Special Concern”). While no nesting Piping Plovers or Least Terns have been observed nesting in this area during recent history4, SBPF will consult with NHESP, the Town Beach Manager, and Town Natural Resources Director prior to conducting any work within the mapped areas to avoid adverse impacts on listed species. 2.3 Updated Bank Contribution Volume Overview As noted in the comments from the independent peer review of the Existing Project5, the standard approach for calculating compensatory nourishment volumes is to multiply the recession rate by the existing landform height and project length to calculate a volume. This standard approach was also used for most of the 10 projects with sand mitigation requirements that were identified by Woods Hole Group in their analysis included as Attachment B to the Existing Project’s Annual Report (the Existing Project’s Annual Report is reproduced here as Attachment E). These ten projects included two on Nantucket, one on Martha’s Vineyard, and seven on Cape Cod. The October 2011 Massachusetts Office of Coastal Zone Management (CZM) Policy Guide provides similar guidance: “When a coastal engineering structure, such as a seawall, revetment, or bulkhead, is legal and determined to be the only feasible alternative, a commensurate volume of compatible material must be periodically placed in the littoral system to compensate 4 Piping plovers and/or Least terns are known to nest north of Hoick’s Hollow and south of the Project area at Low Beach. There have been no documented nests within the NHESP mapped habitat at 61 Baxter Road. The narrow, eroding shoreline is not suitable nesting habitat. 5 April 7, 2017 letter from Greg Berman, WHSG & CCCE to the Commission. 21597/Lighthouse/NOI 2-4 Existing Conditions Epsilon Associates, Inc. for the material that is lost to the system. The volume of material to be required to be placed in the littoral system will be based on calculation of the long-term average annual erosion rate of the coastal landform at the site. Short-term rates can be considered in determining the compensatory volume of material if the issuing authority determines that the short-term rate is more indicative of current and future conditions due to alterations along the shore” (p. 23). Existing Project Bank Contribution Calculations For the Existing Project, the standard approach yielded a bank contribution rate of 12.0 cubic yards per linear foot per year (cy/lf/yr) (see page 10 of “Response to Third Party Review, dated May 2, 2017, and included here as Attachment F). For the Existing Project, SBPF, however, utilized a more conservative approach, which resulted in an average bank contribution rate of 14.3 cy/lf/yr, for the area of 85-107A Baxter Road. The November 1, 2013 memo provided to the Commission during its review of the NOI for the Existing Project (and reproduced here as Attachment G) details how the more conservative calculation was performed. The bank retreat rate was applied to actual cross- sections of each of the lots and the volume contributed from each profile of the bank was then calculated. This more conservative approach yielded 14.3 cy/lf/yr for the Existing Project, which is nearly 20% higher than the standard calculation. Therefore, the more conservative method already incorporates some conservatism over the standard method. Proposed Project Bank Contribution Calculations For the Proposed Project, the bank recession rate was determined for the area from 107-119 Baxter Road and for the area from 71-85 Baxter Road. (71 Baxter Road is the southern extent of top of bank erosion that is discernible on aerial photographs.) The bank recession rate was determined using the same methodology described in Attachment G, where the bank retreat distance was measured in GIS using top of bank lines digitized from 1994, 2003, and 2017. The 2017 top of bank line was derived from the August 2017 aerial survey of the bank. As shown in Tables 2-1 through 2-3 below, the distance-weighted average annual rate of retreat for the area from 71-85 and 107-119 Baxter Road is 2.8 ft/yr. This number is significantly less than the average annual bank retreat of 4.6 ft/yr previously calculated for those areas covered by the Existing Project, which reflects the higher bank erosion in the Existing Project area. Table 2-1 Average Bank Retreat Rates, 107-119 Baxter Rd and 71-85 Baxter Rd Average Annual Bank Retreat (1994-2017) for 107-119 Baxter Road 2.0 Average Annual Bank Retreat (2003-2017) for 71-85 Baxter Road 3.5 Average Distance-Weighted Bank Retreat 107-119 & 71-85 Baxter Road 2.8 21597/Lighthouse/NOI 2-5 Existing Conditions Epsilon Associates, Inc. Table 2-2 Detailed Analysis of Bank Retreat from 1994-2017 at 107-119 Baxter Rd Transect Lot Bank Retreat (Feet) 1994-2017 1 119 23.4 2 119 30.2 3 119 31.4 4 119 33.6 5 119 34.7 6 119 35.4 7 119 35.9 8 119 36.2 9 119 37.1 10 119 41.8 11 117 42.3 12 117 40.4 13 117 38.8 14 117 38.5 15 117 35.3 16 117 33.1 17 117 31.6 18 117 31.6 19 117 34.1 20 117 32.5 21 117 36.8 22 115 40.6 23 115 41.4 24 115 38.9 25 115 35.7 26 115 35.3 27 115 35.4 28 115 34.8 29 115 42.7 30 115 46.9 31 115 46.9 32 113 48.6 33 113 52.4 34 113 50.4 35 113 48.3 36 113 47.4 37 113 43.3 38 113 40.5 39 113 38.1 40 113 38.9 41 113 41.3 21597/Lighthouse/NOI 2-6 Existing Conditions Epsilon Associates, Inc. Table 2-2 Detailed Analysis of Bank Retreat from 1994-2017 at 107-119 Baxter Rd (Continued) Transect Lot Bank Retreat (Feet) 1994-2017 42 Public Access 36.2 43 Public Access 37.0 44 109 37.6 45 109 36.8 46 109 39.6 47 109 42.6 48 109 44.9 49 109 48.1 50 109 51.3 51 109 53.4 52 109 62.0 53 109 64.0 54 109 64.3 55 109 62.0 56 109 62.2 57 109 60.6 58 109 60.5 59 109 62.1 60 107A 62.2 61 107A 57.7 62 107A 54.4 63 107A 54.4 64 107A 54.3 65 107A 53.5 66 107A 54.2 67 107 56.5 68 107 61.4 69 107 60.3 70 107 64.7 71 107 66.2 72 107 65.5 73 107 67.8 74 107 66.5 75 107 67.9 Average Retreat (Ft) 46.3 Average Annual Retreat (Ft/Yr) 2.0 21597/Lighthouse/NOI 2-7 Existing Conditions Epsilon Associates, Inc. Table 2-3 Detailed Analysis of Bank Retreat from 2003-2017 at 85-71 Baxter Rd Transect Lot Bank Retreat (Feet) 2003-2017 76 85 75.1 77 85 71.9 78 85 72.8 79 85 71.8 80 85 73.1 81 85 69.0 82 85 67.0 83 85 66.0 84 85 66.8 85 85 66.3 86 85 65.9 87 85 64.2 88 85 66.5 89 85 71.4 90 85 75.5 91 85 76.2 92 85 74.6 93 85 71.6 94 85 71.7 95 85 74.6 96 85 73.6 97 85 70.3 98 85 71.1 99 85 69.5 100 85 69.2 101 85 72.5 102 83 73.4 103 83 69.7 104 83 62.2 105 83 55.2 106 83 50.2 107 83 49.4 108 83 51.4 109 83 50.1 110 83 48.6 111 83 50.2 112 83 53.7 113 83 54.9 114 83 53.7 115 81 55.4 116 81 58.0 117 81 61.8 118 81 61.5 21597/Lighthouse/NOI 2-8 Existing Conditions Epsilon Associates, Inc. Table 2-3 Detailed Analysis of Bank Retreat from 2003-2017 at 85-71 Baxter Rd (Continued) Transect Lot Bank Retreat (Feet) 2003-2017 119 81 60.0 120 81 56.4 121 81 53.1 122 81 48.9 123 81 47.9 124 81 44.5 125 79 36.0 126 79 38.5 127 79 35.7 128 79 25.6 129 79 17.0 130 79 15.1 131 79 14.4 132 79 14.1 133 79 12.3 134 79 9.8 135 77 14.5 136 77 21.9 137 77 20.5 138 77 19.5 139 77 20.4 140 77 28.9 141 77 28.8 142 77 36.3 143 75 37.5 144 75 41.1 145 75 42.1 146 75 43.7 147 75 42.8 148 75 40.2 149 75 36.8 150 75 43.4 151 73 43.8 152 73 47.9 153 73 48.1 154 73 46.5 155 73 45.1 156 73 39.7 157 73 39.1 158 73 40.0 159 73 43.1 160 73 44.0 161 73 44.6 21597/Lighthouse/NOI 2-9 Existing Conditions Epsilon Associates, Inc. Table 2-3 Detailed Analysis of Bank Retreat from 2003-2017 at 85-71 Baxter Rd (Continued) Transect Lot Bank Retreat (Feet) 2003-2017 162 73 38.3 163 73 38.5 164 73 41.0 165 Public Access 44.0 166 Public Access 26.1 167 Public Access 8.9 168 71 8.9 169 71 10.0 170 71 13.7 171 71 15.0 172 71 15.7 173 71 19.5 174 71 21.1 175 71 10.2 176 71 5.4 Average Retreat (Ft) 48.6 Average Annual Retreat (Ft/Yr) 3.5 Excludes shaded cells at 79 Baxter As noted above, the standard method involves multiplying the bank retreat rate by the landform height and project length to get a volume. This standard approach results in a calculation of a mitigation volumes of 7.7 cy/lf/yr, as shown in Tables 2-4 and 2-5 below. Table 2-4 Bank Height 59-85 Baxter Road and 107-119 Baxter Road Location Top of Bank (ft MLW) Toe of Bank (ft MLW) Bank Height above Toe (ft) 59 Baxter 70 10 60 61 Baxter 70 10 60 63 Baxter 70 10 60 65 Baxter 72 10 62 67 Baxter 72 10 62 69 Baxter 72 10 62 71 Baxter 74 10 64 73 Baxter 78 10 68 75 Baxter 83 10 73 77 Baxter 84 10 74 79 Baxter 86 10 76 81 Baxter 79 10 69 21597/Lighthouse/NOI 2-10 Existing Conditions Epsilon Associates, Inc. Table 2-4 Bank Height 59-85 Baxter Road and 107-119 Baxter Road (Continued) Location Top of Bank (ft MLW) Toe of Bank (ft MLW) Bank Height above Toe (ft) 83 Baxter 80 10 70 85 Baxter 78 10 68 107 Baxter 98 10 88 107A Baxter 100 10 90 109 Baxter 101 10 91 113 Baxter 103 10 93 115 Baxter 104 10 94 117 Baxter 104 10 94 119 Baxter 104 10 94 Average Height (ft) (weighted by distance) 74 Table 2-5 Standard Calculation of Compensatory Mitigation for 59-85 Baxter Road and 107-119 Baxter Road Bank Retreat (ft/yr) Length of Landform (ft) Bank Height (ft) Mitigation Volume 2.8 2853 74 591141.6 cf 21894.133 cy 7.7 cy/lf An average volume was developed using cross-section views of representative lots in the Expanded Project (lots 63, 69, 85, and 117 Baxter Road), using the same methodology described in Attachment G. The distance-weighted average volume calculation for these four representative lots results in an estimated annual bank erosion of 8.6 cy/lf/yr. Average Bank Contribution Volume for Existing and Proposed Project Area A distance-weighted average of 8.6 cy/lf/yr and 14.3 cy/lf/yr was calculated for the complete Project stretch of 71-119 Baxter Road6, with a resulting quantity of 10.0 cy/lf/yr. 6 Bluff recession rates were calculated as far south as 71 Baxter Road, since that is the southern extent of visually discernible top of bank erosion. 21597/Lighthouse/NOI 3-1 Project Description Epsilon Associates, Inc. 3.0 PROJECT DESCRIPTION 3.1 Geotextile Tubes 3.1.1 Overview The Proposed Project will be installed to the north and south of the Existing Project, so as to obtain continuous protection from 597 to 119 Baxter Road (plus returns on lots 55 and 122, as shown in Attachment C). The length of the Proposed Project is 895 feet to the north of the Existing Project (821 feet plus 74 feet of returns) and 1,978 feet to the south of the Existing Project (1,909 feet plus 69 feet of returns), for a total new length of 2,873 feet. The Project includes four tiers of geotextile tubes, each 45-feet in circumference (with approximate dimensions of 19-feet wide and 7-feet tall). The lowest tier will be set at elevation -3.0 feet Mean Low Water (MLW). The Project will be installed so as to directly abut the Existing Project, with no gaps. The Project includes returns at either end. Each set of returns will consist of four 45-foot circumference tubes. 3.1.2 Design Basis As noted above, the Project is designed to provide protection from a 100- to 200-year storm. The Project includes four rows of geotextile tubes, each 45-feet in circumference (with appropriate dimensions of 19-feet wide and 7-feet tall). The lowest tier will be set at elevation -3.0 feet MLW. Stillwater elevations for the 100-year storm were obtained from the June 9, 2014 FEMA Flood Insurance Study (FIS). Still Water Elevations (SWEL) provided in the FIS for the area near the Sconset geotextile tube project (Transect 13). The 1% Chance Occurrence (100 year) SWEL for Transect 13 is 5.8 feet NAVD88. The conversion to MLW is +1.88 feet, yielding a SWEL of 7.68 feet MLW. The crest elevation and base elevation of the geotextile tubes was based on modeling performed with COSMOS (Southgate & Nairn, 1993)8 (Nairn & Southgate, 1993)9. This is a 7 The segments of the Project at 59 Baxter and the southern half of 61 Baxter will not be built until erosion removes the existing small coastal dune. 8 Southgate, H.N. and Nairn, R.B. (1993). Deterministic Profile Modelling of Nearshore Processes. Part I. Waves and Currents. Coastal Engineering, 19. pp. 27-56. 9 Nairn, R.B. and Southgate, H.N. (1993). Deterministic Profile Modelling of Nearshore Processes. Part II. Sediment Transport and Beach Profile Development. Coastal Engineering, 19. pp. 57-96. 21597/Lighthouse/NOI 3-2 Project Description Epsilon Associates, Inc. two-dimensional hydrodynamic model that incorporates waves, wave transformation, wave set-up, longshore currents and sediment transport. Wave data was extracted from the North Atlantic Coast Comprehensive Study (USACE, 2015)10. NACCS Station 684 is located directly offshore of the project site and close to Profile 90.8. Bathymetric survey data had been collected out to the NACCS extraction point. The maximum wave height was 15.4 feet with a 15 second period though a full 96-hour storm event was modeled with varying wave height, wave period and wave direction. The waves were transformed from the NACCS extraction point to the shoreline within COSMOS. October 2016 topographic and bathymetric survey data was applied in the model. A mean grain size of 0.50mm was applied though a sensitivity analysis was performed to evaluate finer sediment. Two storm events were run to remove the covering sand during the first event and then determine maximum scour during the second event. The maximum modeled scour extended to approximately -2 feet MLW, with a recommended installation depth of -3 feet MLW to avoid exposing the bottom of the tube. The maximum wave runup extended to approximately 16 feet MLW. The runup height, plus allowing one foot for relative sea level rise and accounting for the tubes reaching a height of 6-7 feet, necessitates the use of four tiers of geotextile tubes. 3.2 Vegetation Where the bank face is denuded, the Project includes planting American beachgrass and other native vegetation to help stabilize the face of the bank. American Beachgrass has been planted in the area of the Existing Project and is growing well (Figure 14). Where needed, a veneer of sand filling gullies and rivulets, as well as helping to drain areas with organic matter at the surface, will be added prior to vegetation to smooth out the bank face. The Massachusetts Office of Coastal Zone Management (CZM) specifically recommends the use of American beachgrass as the top species for stabilizing coastal banks, due to its fast- growing, dense root system and its tolerance of salt spray and exposure to wind and waves. (http://www.mass.gov/eea/agencies/czm/program-areas/stormsmart-coasts/coastal- landscaping/coastal-bank.html). As stated by CZM, American beachgrass can hold windblown sediments onto bank or bank faces and bind the soil using its fast-growing, dense root system, which allows other species to colonize at the same site. Once the beachgrass has been established, other native woody vegetation recommended in the above-referenced CZM website may be planted in the following years, including: Bearberry, Beach Heather, Bayberry, Beach Plum, and Creeping Juniper. Common juniper 10 USACE (2015). North Atlantic Coast Comprehensive Study: Resilient Adaptation to Increasing Risk. January 2015. http://www.nad.usace.army.mil/CompStudy/ 21597/Lighthouse/NOI 3-3 Project Description Epsilon Associates, Inc. has been excluded as a potential vegetation type since it has been noted that it does not appear to be native to the coastal bank. In certain portions of the Project area, swallows (a species that is not state- or federally-listed) have been known to nest. The Massachusetts Breeding Bird Atlas 2 prepared and maintained by the Massachusetts Audubon Society (Mass Audubon) considers their population stable to increasing on Nantucket. They are not listed as Endangered, Threatened or of Special Concern by the Massachusetts Division of Fisheries and Wildlife. Dr. Robert Kennedy, who has conducted over 95 swallow surveys on the east coast of Nantucket, observed: In the Sankaty Coastal Bank, Bank Swallows only nested 1) where there existed a vertical cliff face of about 5 feet or higher below the top of the coastal bank, 2) within 2 to 4 feet from the top of the coastal bank, 3) where the cliff substrate permitted excavation by the swallows without that substrate collapsing on them, and 4) where the top of the coastal bank is about 25 feet or higher from the active beach.11 Much of the Existing Project area does not have suitable habitat for swallows. However, Dr. Kennedy’s June 2017 survey (reproduced as Attachment H) indicated that there were concentrated swallow cavities present in the area between 109 and 115 Baxter Road. A significant colony of nests was also observed in this location in 2010. Accordingly, while swallows are not a listed species and their population may be increasing on Nantucket, this concentrated area of swallow cavities is a recognized feature and the upper 5 to 7 feet of the bank will not be vegetated in this area (located between 109 and 115 Baxter Road). In all other areas, where swallow nests are sparse or non-existent, vegetation will occur to the top of the bank to facilitate comprehensive slope stabilization. 3.3 Sand Source The sand source for the geotextile tubes and mitigation sand will be the same on-island pits that are used for the Existing Project. If another sand source is identified, grain size information will be provided to the Commission to demonstrate compatibility prior to the use of the new sand source. 3.4 Construction Overview The anticipated duration of construction is four-six months. Construction will proceed according to the following sequence: 1. Construction equipment will access the beach via Hoick’s Hollow. 2. The initial step will be excavating the trench for the lowest tier of geotextile tubes down to elevation -3.0 feet MLW. The trench will be approximately 35-feet wide and 200 feet 11 July 3, 2017 letter from Robert S. Kennedy to the Commission (reproduced as Attachment H). 21597/Lighthouse/NOI 3-4 Project Description Epsilon Associates, Inc. long. Material excavated from the trench will be temporarily placed seaward of the trench. 3. The first section of scour apron with anchor tube will be rolled out inside the trench. The anchor tube will extend to approximately 10-feet from the seaward edge of the bottom tier of geotextile tubes. After the first section of scour apron/anchor tube is in place, the geotextile tubes that make up the lowest tier will be laid out on top of the apron. 4. The lowest tier geotextile tube is inflated by pumping water from the trench into the geotextile tube through portholes until the required shape and elevation is obtained. Sand is then entrained in the water creating an 80/20 water-to-sand slurry mixture that is pumped into portholes in each geotextile tube. The sand falls out within the geotube and the water exits the far end of the geotube through another porthole. The water flows back into the excavation trench. Once fully filled, the porthole sleeves will be rolled up and tucked into the geotextile tube leaving a void of approximately 1 cubic foot. that will be filled with high-strength concrete. These concrete plugs will then be covered with a geotextile patch. 5. Each section of the lowest tier of geotextile tubes will be overlapped with the adjacent geotextile tube. 6. After each segment of the lowest tier of geotextile tubes is filled, the integrated anchor tube will be filled using the same slurry pumping system. This process will be repeated until the lowest tier is completed. Upon completion, the trench will be filled in. 7. Prior to installation of the second tier, some sand from on-island pits (“pit sand”) or other approved compatible source will be spread behind (landward of) the lowest tier to make a “bench” for the second tier. 8. A new water source trench will be excavated seaward of the bottom tier to provide the water used to create the slurry. 9. The tier 2 geotextile tubes will be filled with a sand slurry (as described in #4 above) using pit sand as a sand source. The pit sand will be delivered to the top of the bank and dumped over the top of the bank. 10. The tier 3 geotextile tubes be positioned to overlap with the tier 2 geotextile tube layer. The tier 3 geotextile tubes will be filled with a sand slurry (as described in #4 above). The water source for the slurry will be obtained by excavating a trench seaward of the tier 3 geotextile tube, in a location similar to the water source trench used for the tier 2 geotextile tube. The water source trench will be maintained using the excavated sand to create dikes at its seaward side, landward of the Mean High Water (MHW) line. 11. The area landward of the tier 3 geotextile tube (the “bench”) will be created with sand to match the top of the filled tier 3 geotextile tube. The scour apron will be laid flat on the 21597/Lighthouse/NOI 3-5 Project Description Epsilon Associates, Inc. back (landward) side of the third tube prior to backfilling the bench. This scour apron has a small 3’ circumference anchor tube attached to it; no excavation into the bank will be required to place the scour apron or anchor tube. 12. The tier 4 geotextile tube will be placed and filled in a manner similar to the tier 3 geotextile tube. 13. The returns will be installed by excavating the initial trench for the lowest tiers and then filling all tiers using the slurry system. 14. Once all geotextile tubes are filled, the entire structure will be covered with pit sand using the excavators and the bulldozer. Construction Access All construction equipment will access the beach from Hoick’s Hollow. All construction vehicles will be fueled in the Hoick’s Hollow parking lot area; non-mobile or less-mobile equipment such as the hydraulic pump will be filled on the beach using a small transfer tank. Template Sand Delivery Sand will be delivered from island pits to the site via dump trucks. The dump trucks will deliver the sand to the sand delivery area(s), where it will be pushed over the edge and onto the geotextile tubes below. Sand delivery locations for the Proposed Project include the existing sand delivery area at the access between 85/87 Baxter Road and two new locations: the access between 105/107 Baxter Road and the access between 71/73 Baxter Road. Vegetation Planting of vegetation will not require equipment on the beach or any access via Hoick’s Hollow. Planting will be accomplished by men working on the face of the bank, with access from the top. To ensure vegetation efforts are successful, a minor addition of sand will be added as needed to prepare the planting bed by smoothing out some of the deeper rills and gullies. 3.5 Alternatives Multiple alternatives were considered during extensive hearings on the Existing Project. These previous analyses are also relevant for the Proposed Project. The following information previously-developed for the Existing Project is not repeated here but is incorporated by reference: 1. An Alternatives Analysis was included as Attachment E to the original Revetment NOI filed with the Commission on July 3, 2013 and is reproduced here as Attachment I. This Alternatives Analysis evaluated the following options: Geotextile Tubes, Beach 21597/Lighthouse/NOI 3-6 Project Description Epsilon Associates, Inc. Nourishment, Dewatering, Breakwater, Groin, Seawall, Drift Fence, Coastal Bank Terraces, Marine Mattress and Gabion System, and Revetment. 2. An analysis of alternatives was provided in the supplemental information for the Notice of Intent for the geotextile tubes in a letter prepared by Milone & MacBroom dated October 25, 2013. This is reproduced here as Attachment J. 3. A review of jute/coir was included throughout the record of the Existing Project, including in the March 14, 2014 Supplemental Information presented to the Commission. This is reproduced here as Attachment K. 4. During the SOC process for the Geotextile Tube Project, the use of jute/coir for the upper portion (third, fourth and/or fifth tiers) of the geotextile tube structure was exhaustively evaluated in a supplemental Alternatives Analysis submitted to the Massachusetts Department of Environmental Protection (DEP) on October 23, 2014; this document is reproduced here as Attachment L. In its cover letter issuing the SOC (reproduced here as Attachment M), DEP concurred that “the supplemental [alternatives] analysis supported SBPF's need for a fourth tier and returns composed of geotextile” and did not require the use of jute/coir for any part of the Existing Geotextile Tube Project. These Alternatives Analyses have consistently led to a determination that the preferred alternative for the Project area is geotextile tubes (though a revetment is also considered feasible). As explained in the above documents and throughout the record for the Existing Project, the review of jute/coir has consistently demonstrated that, while a coir/jute system may be appropriate in some situations (such as riverine or low-velocity environments), it is not at all sufficient as an alternative for the Project area. Coir and jute are not recommended for any part of the erosion control structure because they completely lack durability to withstand storm conditions experienced regularly at the site, are designed to completely fail and require frequent replacement, and would require a significant time period (estimated at six-eight weeks or more for a single 900 foot tier) for replacement, during which all or part of the sand template would not be available to the littoral system. As has been demonstrated at the Project site, the failure of the coir/jute terraces leaves the bank vulnerable to catastrophic losses during major, successive, or multi-day storms. Because the Project area has little or no ability to absorb additional bank loss, coir/jute are not considered a viable option. Finally, the purported benefits of the use of jute/coir have been shown to be both minimal and compensated for by the substantial mitigation volume. Based on the significant extent of alternatives analyses prepared for the Existing Project, and on ongoing engineering analyses, geotextile tubes have been identified as the preferred alternative for the Proposed Project area due to their ability to provide protection in the high energy environment at Sconset and the ability to mitigate impacts through careful monitoring and mitigation. 21597/Lighthouse/NOI 3-7 Project Description Epsilon Associates, Inc. 3.6 Wetland Resource Area Impacts The installation of the geotextile tubes and associated Project components will permanently impact Coastal Beach, Coastal Bank, and Land Subject to Coastal Storm Flowage through the construction of the geotextile tubes. The Project will also temporarily impact Coastal Beach through the use of temporary water source trenches. These temporary trenches will be located landward of the Mean High Water (MHW) line and will be used as a water source for the sand/water slurry used to fill the geotextile tubes. After the geotextile tubes are filled, the water source trenches will be backfilled and the beach will be restored. Table 3-1 Wetland Resource Impacts Wetland Resource Area Impacts (Linear Feet [LF] or Square Feet [SF]) Coastal Bank 2,873 LF Coastal Beach 67,000 SF (Geotextile tubes)1 105,000 SF (Temporary water source trench) Land Subject to Coastal Storm Flowage 335 SF (Geotextile tubes) 1. The 67,000 SF impact includes both the geotextile tubes and scour apron buried beneath the beach and the geotextile tubes installed above the beach level. 21597/Lighthouse/NOI 4-1 Monitoring and Mitigation Epsilon Associates, Inc. 4.0 MONITORING AND MITIGATION 4.1 Monitoring The Project proposes to follow the monitoring requirements from the DEP File No. SE48- 2824 Order of Conditions, as adjusted by the recommendations in the Existing Project’s Annual Report submitted to the Commission on December 13, 2017 (and included here as Attachment E). ♦ Aerial bank monitoring is proposed annually to provide an assessment of bank volume change in protected and unprotected areas, as well as the volume of sand remaining in the sand template. ♦ Shoreline surveys are proposed twice a year at existing transects (Figures 15 and 16). o Shoreline monitoring frequency will occur a maximum of two times a year. As presented in Attachment B of the Existing Project’s Annual Report (included here as Attachment E), a seasonal analysis of the shoreline position was conducted to determine if particular times of year are more indicative of overall shoreline change. This analysis did not reveal meaningful season variability; trends and variability are similar regardless of season. Annual and longer term trends will be resolved with surveys a maximum of twice per year. Quarterly sampling and observation does not inform the analysis to any greater degree. Therefore, we propose a survey frequency of a maximum of two times a year. This also is consistent with the monitoring suggestions in the MassDEP Beach Nourishment Best Practices Guide (MassDEP, 2007), which suggest seasonal surveys for a year or so, followed by annual surveys for monitoring beach nourishment projects. The National Research Council also recommends a similar approach to beach profile monitoring, which suggests reducing the frequency of surveys over time (National Academy Press, 1995). To be consistent with standard engineering practice, which typically is focused on capturing an eroded “winter” profile along with a recovered “summer” profile after more quiescent periods, if there will be two surveys per year, one survey is proposed for late winter / early spring and the other is proposed in late summer. These surveys also would be consistent with and comparable to long-term data. o Plots of shoreline trends will be included in ongoing shoreline monitoring reports. o Data will be collected to 0 MLW. As presented in Attachment B of the Existing Project’s Annual Report (reproduced here as Attachment E), wading shots are conducted to collect data from 0 to -5 feet MLW and require a rod man adequately equipped to swim in the water, and a survey rod capable of withstanding the conditions. Each individual survey point can take several attempts as the rodman finds safe footing in the surf, and as a surveyor with a transit on the beach gains a 21597/Lighthouse/NOI 4-2 Monitoring and Mitigation Epsilon Associates, Inc. visual fix on the survey rod. An analysis of extrapolating the data from 0 to -5 feet MLW, as opposed to using a rodman to collect the data, shows that associated errors are small (the average difference in the volume of sand estimated for each profile was 1.1 cy/ft, which equates to a 1.4% difference) The surveys can be completed in approximately half the time if there are no wading shots, which would add tremendous flexibility to completing the surveys in timely fashion, and also reduces inherent risks to the survey crew. o Bathymetry monitoring is proposed once per year. The bathymetry offshore Siasconset features a generally stable profile, particularly in the northern and central portions of the monitoring area (which includes the geotextile tubes). Bathymetry data are helpful for general scientific purposes to understand regional coastal processes (e.g., offshore shoal movements and evolutions), but are not conclusive for determining whether the geotextile tubes are having an adverse impact upon adjacent beaches. Shoreline position data are most useful for that purpose. Bathymetry surveys conducted a maximum of once per year are sufficient to characterize regional morphology. In addition, fewer transects could be surveyed (particularly in the northern portion of the monitoring area) without sacrificing information to understand the regional processes. Reducing the total number of bathymetry survey profiles to ~22 that extend no more than the -25 to 35 foot contour would potentially allow for the survey to be completed in a single calm sea/weather day without sacrificing substantive information. To provide useful data for present and long-term comparisons, the subset of ~22 profiles are proposed to include the historic whole number profiles 81 through 99 plus profiles Q, S, and W. Additionally, we propose that bathymetry monitoring be re-evaluated annually to assess its continued value. ♦ Underwater video monitoring is proposed once every three years or in the event that regular monitoring indicates that the sand mitigation template is contributing several (3-5) times more sand than the unprotected bank. ♦ It is proposed that the current wetland well monitoring be discontinued, as no adverse effects have been identified or are anticipated. 4.2 Mitigation As with the Existing Project, sand mitigation is proposed as part of the Proposed Project. The mitigation requirement for the Existing Project is to place a minimum of 22 cy/lf/yr annually. As has been noted in previous submissions (see November 1, 2013 memorandum from Epsilon Associates reproduced here as Attachment G), the average annual bank contribution volume, calculated from 1994-2013, is 12-14.3 cy/lf/yr (depending on calculation methodology). The conservative volume of 22 cy/lf/yr is 1.5-1.8 times the average bank contribution. A review of ten comparable bank and dune protection projects presented 21597/Lighthouse/NOI 4-3 Monitoring and Mitigation Epsilon Associates, Inc. in Attachment B of the Existing Project’s Annual Report (reproduced here as Attachment E) indicates that associated mitigation volumes are based upon average annual erosion of the bank or shoreline multiplied by the height and length of the shoreline protected. This review demonstrates that the significant mitigation required at Sconset (equivalent to 1.5-1.8 times the bank contribution volume) is uniquely conservative. The conservative nature of the mitigation volume sand is evidenced by the fact that significant volumes of mitigation sand are remaining in the sand template at the each of each winter. In summer 2017, the volume of sand remaining in the template at the end of the winter was approximately 17,000 cy. A substantial volume of sand (about 15,000 cy) was also available in 2016 after the end of the winter. The updated bank contribution calculations indicate that the annual, distance-weighted bank contribution volume for the area from 71 to 119 Baxter Road is 10.0 cy/lf/yr. For the Proposed Project, SBPF proposes a more adaptive mitigation program, where the full mitigation volume of 22 cy/lf will be available each year for the winter storm season, but will not be indiscriminately placed annually regardless of how much sand remains in the template. The proposed mitigation plan is to place the full 22 cy/lf in the sand template prior to the start of the storm season each fall. Consistent with current practice, each time the seaward portion of the sand cover washes away as designed during storm events, the sand template will be re-graded (sand from the top will be pushed down) so that the geotextile tubes remain covered and sand is available to the littoral system. Each following year (prior to the start of the storm season), a sufficient volume of sand will be added to refill the sand template to 22 cy/lf, so that 22 cy/lf is always available at the start of each storm season. We believe this mitigation approach will be much more adaptive and will allow the mitigation sand requirement to more closely mimic natural conditions. The proposed mitigation approach recognizes that not all of sand template is washing away each year. As noted above, in 2017, about 17,000 cy of sand remained in the template after the storm season ended, even though the volume of sand contributed from the sand template was higher than the volume of sand contributed from the unprotected bank. The proposed approach avoids increasing the height of the template each year to accommodate another full placement of 22 cy/lf even though ample sand remains, and instead simply refills the sand to the 22 cy/lf mark each year. Continuing to increase in height of the sand template each year is not recommended because it covers the existing bank vegetation and steepens the access ramps, making pedestrian and equipment access and template management activities (such as re-grading) more difficult. 4.3 Failure Criteria The same “failure criteria” from the Order of Conditions for the Existing Project (reproduced here as Attachment N) are recommended for the Proposed Project: a. Failure to provide the sand mitigation as required herein. 21597/Lighthouse/NOI 4-4 Monitoring and Mitigation Epsilon Associates, Inc. b. Failure to conduct the shoreline monitoring and post-storm monitoring as required herein. c. Failure to repair and/or replace damaged geotextile tubes in a timely manner. If repair or replacement cannot be accomplished within 30 days from the date of the damage, SBPF shall notify the Department and the NCC before 30 days have elapsed and provide a repair schedule for Department review and approval. d. Excessive loss in updrift or downdrift beach cross section that can be attributed to the project. If the shoreline monitoring program identifies excessive loss to the adjacent shoreline (compared to historical data) that may be attributable to the project, then SBPF shall provide notice to the Department and the NCC within 30 days of the completion of the quarterly survey. Upon such notice the procedures set forth in the SOC for such circumstances shall apply. e. Failure to maintain adequate beach width in front of the Bank. If the beach in the project area erodes so that the position of MHW migrates landward to the seaward edge of the second tier of geotextile tubes for any two consecutive surveys, then within 30 days of completion of the second quarterly survey SBPF shall provide notice to the Department and the NCC. f. Failure to maintain a walkable beach in front of the geotextile tubes. It shall be a failure if the beach on the seaward side of the coastal bank is not passable by foot and has narrowed by a greater percentage in comparison to the widths of nearby and adjacent beaches up-drift and down-drift, including those beaches in front of other forms of erosion control, for the majority of two consecutive quarters, considering storms, tides, and similar conditions. It is understood that the portion of the beach in front of the geotextile tubes is by definition narrower than nearby unprotected beaches because the geotextile tubes and the sand template covers the back of the beach. In calculating whether the beach has narrowed disproportionately the distance will be measured from Mean High Water to the natural toe of the bluff which in some locations is buried behind the erosion protection system. Upon such a failure SBPF, shall provide notice to the Department and the NCC within 30 days. g. Failure to maintain all required insurance, permits and licenses. h. Failure to meet reporting requirements or good faith effort to provide required reporting. Should any of the failure criteria be met, SBPF will schedule an appearance the Conservation Commission. The Commission shall review he failure and determine how SBPF shall act to address it. In the event removal of the geotextile tubes is ordered, then the geotextile fabric shall be cut, removed, and properly disposed of. Following the removal of the geotextile fabric, sand from the geotextile tubes shall be spread along the beach landward of MHW. 21597/Lighthouse/NOI 4-5 Monitoring and Mitigation Epsilon Associates, Inc. SBPF and the Town shall maintain the escrow fund in place as of the date of the Order of Conditions for the Existing Project (9/30/2015) to ensure the availability of funds to pay for the removal of the geotextile tubes. 21597/Sconset/NOI 5-1 Regulatory Consistency Epsilon Associates, Inc. 5.0 REGULATORY CONSISTENCY Wetland resource areas are described in Section 2.2. The Project’s consistency with applicable state and local wetlands regulations is presented below. 5.1 Compliance with State Wetlands Regulations The installation of the Project will require authorization under the WPA for work occurring within the following wetland resource areas: Coastal Bank, Coastal Beach, and Land Subject to Coastal Storm Flowage. The protected interests within the wetland resource areas the project area include storm damage prevention, flood control, and protection of wildlife habitat. The following sections assess Project compliance with the state wetlands regulations for each resource area. Coastal Bank (310 CMR 10.30) Coastal Bank is defined at 310 CMR 10.30(2) as “the seaward face or side of any elevated landform, other than a coastal dune, which lies at the landward edge of a coastal beach, land subject to tidal action, or other wetland.” The state wetlands regulation at 310 CMR 10.30 includes the following conditions: “WHEN A COASTAL BANK IS DETERMINED TO BE SIGNIFICANT TO STORM DAMAGE PREVENTION OR FLOOD CONTROL BECAUSE IT SUPPLIES SEDIMENT TO COASTAL BEACHES, COASTAL DUNES OR BARRIER BEACHES, 310 CRM 10.30(3) through (5) SHALL APPLY.’ “WHEN A COASTAL BANK IS DETERMINED TO BE SIGNIFICANT TO STORM DAMAGE PREVENTION OR FLOOD CONTROL BECAUSE IT IS A VERTICAL BUFFER TO STORM WATERS, 310 CMR 10.30(6) through (8) SHALL APPLY.” The coastal bank in the Project area supplies sand to nearby coastal landforms; therefore, it is significant to storm damage prevention and flood control. The coastal bank in the Project area also is significant to storm damage prevention and flood control because it is a vertical buffer to storm waters. The following sections describe how the Project design complies with state regulations for coastal banks (310 CMR 10.30(3) through (8)). 310 CMR 10.30(3) – Performance Standard “No new bulkhead, geotextile tube, seawall, groin or other coastal engineering structure shall be permitted on such a coastal bank except that such a coastal engineering structure shall be permitted when required to prevent storm damage to buildings constructed prior to the effective date of 310 CMR 1.21 through 10.37 or constructed pursuant to a Notice 21597/Sconset/NOI 5-2 Regulatory Consistency Epsilon Associates, Inc. of Intent filed prior to the effective date of 310 CMR 10.21 through 10.37 (August 10, 1978), including reconstructions of such buildings subsequent to the effective date of 310 CMR 10.21 through 10.37, provided that the following requirements are met: (a) a coastal engineering structure or modification thereto shall be designed and constructed so as to minimize, using best available measures, adverse effects on adjacent or nearby coastal beaches due to changes in wave action, and (b) the applicant demonstrates that no method of protecting the building other than the proposed coastal engineering structure is feasible. (c) Protective planting designed to reduce erosion may be permitted.” Project Compliance: The Project is necessary to prevent storm damage to buildings and public infrastructure constructed prior to August 10, 1978, including reconstructions of such buildings. Figure 9 shows the status of the lots in terms of which have pre-1978 structures or houses on them and Section 2.1 demonstrates that protection throughout the Project area is required to protect pre-1978 homes. The Project conforms to the other requirements of this regulation, as described below: Coastal Engineering Structure: With respect to subsection (a) above, the geotextile tubes have been designed and will be constructed using best available measures to minimize adverse effects on adjacent or nearby coastal beaches caused by changes in wave action. Best Available Measures are defined at 310 CMR 10.04 as “the most up-to-date technology or the best designs, measures or engineering practices that have been developed and that are commercially available.” The Project also incorporates design features that will minimize the potential for adverse effects on adjacent beaches due to changes in wave action. First, the sloped design of the geotextile tubes will minimize wave reflection or focusing of wave energy onto adjacent, unprotected areas of the bank along the shoreline. Second, the sand mitigation program will minimize impacts on adjacent beaches. No other feasible protection: With respect to subsection (b) above, the Alternatives Analyses referenced in Section 3.5 demonstrate that there is no other feasible method of protecting the existing buildings in the Project area in the long-term other than the proposed geotextile tubes. Protective Plantings: With respect to subsection (c) above, the Project design includes native vegetation plantings to protect the upper bank face and reduce runoff-related erosion. 21597/Sconset/NOI 5-3 Regulatory Consistency Epsilon Associates, Inc. 310 CMR 10.30(4) - Performance Standard “Any project on a coastal bank or within 100 feet landward of the top of a coastal bank, other than a structure permitted by 310 CMR 10.30(3), shall not have an adverse effect due to wave action on the movement of sediment from the coastal bank to coastal beaches or land subject to tidal action.” Project Compliance: The Project is being permitted under 310 CMR 10.30(3), and thus this standard does not apply. 310 CMR 10.30(5) - Performance Standard “The Order of Conditions and the Certificate of Compliance for any new building within 100 feet landward of the top of a coastal bank permitted by issuing authority under M.G.L. c. 131, § 40 shall contain the specific condition: 310 CMR 10.30(3), promulgated under M.G.L. c. 131, § 40, requires that no coastal engineering structure, such as a bulkhead, geotextile tube, or seawall shall be permitted on an eroding bank at any time in the future to protect the project allowed by this Order of Conditions.” Project Compliance: This standard does not apply to this NOI because the proposed Project does not include the construction of any new buildings. 310 CMR 10.30(6) - Performance Standard “Any project on such a coastal bank or within 100 feet landward of the top of such a coastal bank shall have no adverse effects on the stability of the coastal bank.” Project Compliance: The Project has been designed to maintain the stability of the coastal bank; thus, it complies with this standard. 310 CMR 10.30(7) - Performance Standard “Bulkheads, geotextile tubes, seawalls, groins or other coastal engineering structures may be permitted on such a coastal bank except when such bank is significant to storm damage prevention or flood control because it supplies sediment to coastal beaches, coastal dunes, and barrier beaches.” Project Compliance: As described above, the coastal bank in the Project area provides sand to the coastal beach and adjacent coastal system. However, the Project is designed to stabilize the existing bank face in accordance with 310 CMR 10.30(3) and sand mitigation and shoreline monitoring will be conducted to ensure that downdrift beaches are not impacted. If shoreline monitoring demonstrates that the revetment is causing impacts, sand nourishment will be provided to mitigate for this geotextile tube. 21597/Sconset/NOI 5-4 Regulatory Consistency Epsilon Associates, Inc. 310 CMR 10.30(8) - Performance Standard “Notwithstanding the provisions of 310 CMR 10.30(3) through (7), no project may be permitted which will have any adverse effect on specified habitat sites of rare vertebrate or invertebrate species, as identified by procedures established under 310 CMR 10.37.” Project Compliance: The Project area for initial installation is largely outside estimated habitat indicated on the most recent Estimated Habitat Map of State-Listed Rare Wetlands Wildlife published by the NHESP (NHESP 2008 Atlas, MassGIS) (see Figure 13). Lot 61 is within mapped habitat, and the SBPF will consult with NHESP through the filing of this NOI. Coastal Beaches (310 CMR 10.27) Coastal Beach is defined at 310 CMR 10.27(2) as “unconsolidated sediment subject to wave, tidal and coastal storm action which forms the gently sloping shore of a body of salt water and includes tidal flats. Coastal beaches extend from the mean low water line landward to the dune line, coastal bankline or the seaward edge of existing man-made structures when these structures replace one of the above lines, whichever is closest to the ocean.” The state wetlands regulation at 310 CMR 10.27(2) includes the following conditions: “WHEN A COASTAL BEACH IS DETERMINED TO BE SIGNIFICANT TO STORM DAMAGE PREVENTION, FLOOD CONTROL, OR PROTECTION OF WILDLIFE HABITAT, 310 CMR 10.27(3) through (7) SHALL APPLY.” The coastal beach in the Project area dissipates wave energy, reduces the height of approaching waves, and acts as a sand source to nearby coastal landforms. It also provides habitat for non-listed and listed foraging shorebirds. As such, the coastal beach is significant to storm damage prevention, flood control, and the protection of wildlife habitat. As discussed below, the Project is designed to comply with state regulations for coastal beaches 10.27(3) through (7). 310 CMR 10.27(3) – Performance Standard “Any project on a coastal beach, except any project permitted under 310 CMR 10.30(3)(a), shall not have an adverse effect by increasing erosion, decreasing the volume or changing the form of any such coastal beach or an adjacent or downdrift coastal beach.” Project Compliance: As explained above, the Project is being permitted under 310 CMR 10.30(3)(a). Therefore, this standard does not apply. 21597/Sconset/NOI 5-5 Regulatory Consistency Epsilon Associates, Inc. 310 CMR 10.27(4) – Performance Standard “Any groin, jetty, solid pier or other such solid fill structure which will interfere with littoral drift, in addition to complying with 310 CMR 10.27(3), shall be constructed as follows: (a) It shall be the minimum length and height demonstrated to be necessary to maintain beach form and volume. In evaluating necessity, coastal engineering, physical oceanographic and/or coastal geologic information shall be considered. (b) Immediately after construction any groin shall be filled to entrapment capacity in height and length with sediment of grain size compatible with that of the adjacent beach. (c) To transfer sediments to the downdrift side of the inlet or shall be periodically redredged to provide beach nourishment to ensure that downdrift or adjacent beaches are not starved of sediments.” Project Compliance: This standard does not apply. The Project is located above the zone of littoral drift (i.e., at the landward edge of the coastal beach). 310 CMR 10.27(5) – Performance Standard “Notwithstanding 310 CMR 10.27(3), beach nourishment with clean sediment of a grain size compatible with that on the existing beach may be permitted.” Project Compliance: The Project includes clean sand mitigation from on-island source previously approved by the Commission. 310 CMR 10.27(6) – Performance Standard “In addition to complying with the requirements of 310 CMR 10.27(3) and 10.27(4), a project on a tidal flat shall if water-dependent be designed and constructed, using best available measures, so as to minimize adverse effects, and if non-water-dependent, have no adverse effects, on marine fisheries and wildlife habitat cause by: (a) alterations in water circulation, (b) alterations in the distribution of sediment grain size, and (c) changes in water quality, including, but not limited to, other than natural fluctuations in the levels of dissolved oxygen, temperature or turbidity, or the addition of pollutants.” 21597/Sconset/NOI 5-6 Regulatory Consistency Epsilon Associates, Inc. Project Compliance: This standard does not apply. The Project does not include any work on a tidal flat, which is defined at 310 CMR 10.27(2) as “any nearly level part of a coastal beach which usually extends from the mean low water line landward to the more steeply sloping face of the coastal beach, or which may be separated from the beach by land under the ocean.” All proposed Project activities will occur on the coastal bank and at the toe of the coastal bank on a narrow strip of the coastal beach well landward of and above the steeply sloping beach face. 310 CMR 10.27(7) – Performance Standard “Notwithstanding the provisions of 310 CMR 10.27(3) through 10.27(6), no project may be permitted which will have any adverse effect on specified habitat sites or rare vertebrate or invertebrate species, as identified by procedures established under 310 CMR 10.37.” Project Compliance: The Project area for initial installation is largely outside estimated habitat indicated on the most recent Estimated Habitat Map of State-Listed Rare Wetlands Wildlife published by the NHESP (NHESP 2008 Atlas, MassGIS) (see Figure 13). Lot 61 is within mapped habitat, and the SBPF will consult with NHESP through the filing of this NOI. Land Subject to Coastal Storm Flowage Land Subject to Coastal Storm Flowage is defined at 310 CMR 10.04 as “… land subject to any inundation caused by coastal storms up to and including that caused by the 100-year storm, surge of record or storm of record, whichever is greater”. The Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) for the Project area, which defines the 100-year storm elevations, is provided as Figure 11. Project Compliance: There are no performance standards in the state wetlands regulations for Land Subject to Coastal Storm Flowage (LSCSF). However, since LSCSF overlays the coastal beach and the coastal bank up to the 100-year storm elevation as shown on Figure 11, the relevant performance standards have been reviewed and addressed above. 5.2 Compliance with Local Wetlands Regulations The Project requires authorization under the Nantucket Wetlands Bylaw for work occurring within the following wetland resource areas: Coastal Bank, Coastal Beach, and Land Subject to Coastal Storm Flowage. The protected interests within these wetland resource areas include storm damage prevention, flood control, protection of wildlife habitat, and wetland scenic views. 21597/Sconset/NOI 5-7 Regulatory Consistency Epsilon Associates, Inc. Nantucket Coastal Banks (Section 2.05) “Bank (coastal)” is defined in Section 1.02 of the local wetlands regulations as “the seaward face or side of any elevated land form, other than coastal dune, which lies at the landward edge of coastal beach, coastal dune, land subject to tidal action or coastal storm flowage, or other coastal wetland. Any minor discontinuity of the slope notwithstanding, the top of the bank shall be the first significant break in slope as defined by site specific topographic plan information, site inspection, wetland habitat evaluation, geologic origin, and /or relationship to land subject to coastal storm flowage. A bank may be partially or totally vegetated, or it may be comprised of exposed soil, gravel, stone or sand. A bank may be created by man and/or made of man-made materials. A bank may or may not contribute sediment to coastal dunes, beaches and /or to the littoral drift system. A bank may be significant as a major source of sediment, as a vertical buffer, for wildlife habitat and for wetland scenic views.” Performance Standards for work on coastal banks are set forth in Section 2.05 B of the local wetlands regulations, which provides that “Coastal Banks or Land within 100 feet of a Coastal Bank shall be presumed significant to the Interests Protected by the Bylaw as referenced in Section A, therefore the following regulations shall apply.” The Project does not include structures subject to the performance standards listed below, and hence they are excluded from the following discussion: ♦ Section 2.05 B(2) (piers); ♦ Section 2.05 B(4) (elevated walkways); ♦ Section 2.05 B(6) (septic leach facility); and ♦ Section 2.05 B(8) (buildings). The remaining applicable sections of the local wetlands regulations pertaining to coastal bank are addressed below. Section 2.05 B(1) – Performance Standard “No new bulkheads, coastal geotextile tubes, groins, or other coastal engineering structures shall be permitted to protect structures constructed, or substantially improved, after 8/78 except for public infrastructures. Bulkheads and groins may be rebuilt only if the Commission determines there is no environmentally better way to control an erosion problem, including in appropriate cases the moving of the threatened buildings and/or public infrastructure. Other coastal engineering structures may be permitted only upon a clear showing that no other alternative exists to protect a structure that has not been substantially improved or public infrastructure built prior to 9/78, from imminent danger.” Project Compliance: The Project objectives are to protect Baxter Road and other infrastructure and to preserve an entire historic largely pre-78 community, which necessarily includes a number of post-78 homes as well as pre-78 structures to which various alterations 21597/Sconset/NOI 5-8 Regulatory Consistency Epsilon Associates, Inc. have been made. In addition, the project objectives include protecting and possibly extending the ‘Sconset Foot-path, and proposed public access ways to the Foot-path and to the beach between properties. Note that many houses have already been moved, others have little room to move, and the Town voted for the Existing Project recognizing that infrastructure is in imminent danger and should be protected in place. The Memorandum of Understanding entered into in July 2013 by the Town and SBPF specifically recognized that “certain private homes located on or near Siasconset Bluff and Baxter Road, a public way, may be imminently threatened with damage and/or loss and destruction due to severe erosion of the bluff” and specifically planned for up to 4,000 feet of a coastal erosion structure in the areas included in the Existing Project Area and Proposed Project Area (see Attachment O). Bank recession is progressing from north to south and many homes have been forced to move off their lots or have been lost to erosion (see Attachment D). An analysis of bank retreat prepared for the Existing Project documented that single-season bank recession rates could be as high as 40-feet, based on measured bank recession from 2012-2013 (this document is reproduced here as Attachment P). The homes and infrastructure in the Project area are all in imminent danger because they could be destroyed if another season or two of significant bank erosion occurs. The Project does not involve rebuilding any bulkhead or groin. The Alternatives Analysis referenced in Section 3.5 demonstrate that no other alternative is feasible to satisfy the project objectives. Section 2.05 B(3) - Performance Standard “All projects shall be restricted to activity determined by the Commission to have no adverse effect on bank height, bank stability, wildlife habitat, vegetation, wetland scenic view, or the use of a bank as a sediment source.” Project Compliance: The Project will not have any adverse effect on bank height, bank stability, wildlife habitat, vegetation, wetland scenic view, or the use of a bank as a sediment source as described below. ♦ Bank height: The Project will preserve rather than adversely affect bank height, as it does not involve any work which would lower the bank height. ♦ Bank stability: As designed, the Project is intended to maintain bank stability by protecting the lower bank from wave-induced erosion. Vegetation plantings on the upper bank face will also prevent rain- and wind-induced erosion. ♦ Wildlife habitat: The Project will not adversely impact wildlife habitat. Bank vegetation will be restored as described in Section 3.2. ♦ Vegetation: Planting beach grass and other native vegetation on the bank face will enhance vegetation in the Project area. 21597/Sconset/NOI 5-9 Regulatory Consistency Epsilon Associates, Inc. ♦ Wetland scenic view: As shown by Figures 3-8, the geotextile tubes with the sand cover and associated vegetation will have wetland scenic views similar to bank appearance before it was denuded by erosion. ♦ Sediment Source: With respect to the bank as a sediment source, although the Project is designed to stabilize the existing bank in accordance with local performance standard Section 2.05 B(1) and state performance standard 310 CMR 10.30(3), the Project also provides sand mitigation and includes monitoring of adjacent and downdrift beaches. Section 2.05 B(5) - Performance Standard “All projects which are not water dependent shall maintain at least a 25-foot natural undisturbed area adjacent to a coastal bank. All structures which are not water dependent shall be at least 50 feet from a coastal bank.” Project Compliance: “Water Dependent Projects or Uses” are defined in the local wetlands regulations as “projects which require direct access for their intended use and therefore cannot be located out of the Area Subject to Protection under the Bylaw. Examples include but are not limited to: docks, piers, boat landings, boathouses, marinas, stairs to beaches, and boardwalks over wetland vegetation. Projects which benefit from wetlands access but which do not require it are not water dependent uses. Examples include: restaurants, dwellings, and commercial enterprises servicing marine-related uses such as fish markets, repair facilities, ships’ chandleries, and general use recreational trails.” The Project is water dependent because direct access to the coastal bank and coastal beach is required to achieve the intended purpose of the Project in stabilizing the coastal bank to provide storm damage prevention and flood control. This Project cannot be located out of the coastal bank and coastal beach resource areas. The Project will also include preserving and enhancing recreational trails and beach access. Section 2.05 B(7) - Performance Standard “In areas of an eroding coastal bank, the distance from all new structures to the coastal bank shall be at least 20 times the average annual erosion rate or 100 feet, whichever is the lesser. The average annual erosion rate shall be determined by averaging the annual erosion over a 150-year period ending with the date the NOI was filed, or if no NOI was filed, the date construction began. If erosion data is not available for the 150 year period, the Commission shall determine the average annual erosion rate from such lesser time for which erosion data is available. In cases where documentation can be provided to show that the use of the I50- year period is inappropriate to existing coastal shoreline characteristics and trends, alternate shoreline change rates may be used with the approval of the Commission.” 21597/Sconset/NOI 5-10 Regulatory Consistency Epsilon Associates, Inc. Project Compliance: This regulation is designed to ensure a substantial setback for new structures built on the land above an eroding coastal bank. The Project does not involve construction of any new buildings or other structures at the top of the coastal bank that might require future protection; therefore, this standard does not apply. Nantucket Coastal Beaches (Section 2.02) “Beach” is defined in Section 1.02 of the local wetlands regulations as “unconsolidated sediment subject to wave, tidal, or storm action which forms the gently sloping shore of a body of water, including land which is separated from other land by a body of water or marsh system. Beaches extend from the mean low water line landward to the dune line, bank line, or the edge of existing man-made structures, when these structures replace one of the above lines, whichever is closest to the defining water body.” Performance Standards for coastal beaches are set forth in Section 2.02 B of the local wetlands regulations, which provides that “[a] Coastal Beach, Tidal Flat or Land within 100 feet of a Coastal Beach or Tidal Flat shall be presumed significant to the interests Protected by the Bylaw, as referenced in Section A, therefore the following regulations shall apply:” The Project does not include activities or structures subject to the following performance standards, and hence they are excluded from the subsequent discussion: ♦ Section 2.02 B(3) (dredging); ♦ Section 2.02 B(5) (septic systems); ♦ Section 2.02 B(6) (non-water dependent activities); ♦ Section 2.02 B(7) (new buildings); and ♦ Section 2.02 B(8) (vehicular access for houses and recreational areas). The remaining applicable sections of the local wetlands regulations pertaining to coastal beach are addressed below. Section 2.02 B(1) – Performance Standard “The provisions of Section 2.01 B(1-8) (Land Under the Ocean) shall apply to coastal beaches and tidal flats.” Project Compliance: “Land Under the Ocean” is not defined in the local wetlands regulations. Therefore, in accordance with Section 1.02, “To the extent not defined herein or in the Bylaw, words used in the Bylaw or in the regulations shall have the definitions contained in the Massachusetts Wetlands Protection Act (M.G.L. c. 131, sec. 40) and the rules and regulations promulgated thereunder.” “Land Under the Ocean” is defined in the state wetland regulations at 310 CMR 10.25(2) to mean “land extending from the mean low water line seaward to the boundary of the municipality’s jurisdiction and includes land under estuaries.” 21597/Sconset/NOI 5-11 Regulatory Consistency Epsilon Associates, Inc. The Project does not involve any work seaward of the mean low water line; therefore, none of the performance standards at Section 2.01 B(1-8) of the local wetlands regulations apply. However, even if these performance standards did apply, the Project does not include activities or structures subject to the following performance standards: ♦ Section 2.01 B(1) (improvement and maintenance dredging); ♦ Section 2.01 B(2) (dredging); ♦ Section 2.01 B(3) (residential piers); ♦ Section 2.01 B(4) (commercial piers); ♦ Section 2.01 B(5) (commercial or residential piers); ♦ Section 2.01 B(6) (aquaculture); and ♦ Section 2.01 B(9) (non-water dependent project). If Section 2.01 B were applicable, the only standards in Section 2.01 B that would be relevant are those provided in 2.01 B(7) (coastal engineering structure) and 2.01 B(8) (water dependent project), which are both discussed below for informational purposes only: Section 2.01 B(7) – Performance Standard “No new bulkheads or coastal engineering structures shall be permitted to protect structures constructed or substantially improved after 8/78. Bulkheads may be rebuilt only if the Commission determines that there is no environmentally better way to control an erosion problem, including in appropriate cases the moving of the threatened building. Other coastal engineering structures may be permitted only upon a clear showing that no other alternative exists to protect a structure built prior to 9/78, but not substantially improved, from imminent danger.” Project Compliance: Project compliance with the language of this standard is described below under Section 2.02 B(2). Section 2.01 B(8) – Performance Standard “Water dependent projects shall be designed and performed so as to cause no adverse effects on wildlife, erosion control, marine fisheries, shellfish beds, storm damage prevention, flood control, and recreation.” Project Compliance: As described in Section 2.05 B(5), the Project is water dependent because it requires direct access to the coastal bank and landward portion of the coastal beach. ♦ Wildlife: See previous discussion under Section 2.05 B(3). ♦ Erosion Control: The Project will have a positive effect on erosion control, as it will protect the bank from wave-induced erosion and sand mitigation will be added to mimic the natural sand supply from the coastal bank. 21597/Sconset/NOI 5-12 Regulatory Consistency Epsilon Associates, Inc. ♦ Marine Fisheries and Shellfish beds: No Project activities will occur seaward of Mean High Water, and hence the Project will not have any adverse effects on marine fisheries or shellfish beds. ♦ Storm damage prevention and flood control: Storm damage prevention and flood control will benefit from the Project since it will protect the coastal bank. Sand mitigation will be provided and shoreline monitoring will be conducted to ensure that adjacent and downdrift beaches are not impacted. ♦ Recreation: The Project will not adversely impact recreational uses along the beach or in the water, as it will be located on the coastal bank and a portion of the coastal beach. The Project will maintain public access in front of or on top of the geotextile tubes. Section 2.02 B(2) – Performance Standard “No new bulkhead or coastal engineering structure shall be permitted to protect structures constructed, or substantially improved, after 8/78. Bulkheads may be rebuilt only if the Commission determines there is no environmentally better way to control an erosion problem, including in appropriate cases the moving of the threatened building. Other coastal engineering structures may be permitted only upon a clear showing that no other alternative exists to protect a structure built prior to 9/78, and not substantially improved, from imminent danger.” Project Compliance: Project compliance with this standard is discussed below. ♦ Protect Buildings: The Project is designed to preserve an entire historic largely pre- 1978 community, which necessarily includes a number of post-1978 homes as well as pre-1978 structures to which various additions have been made. See Section 2.1 above. Not all of the pre-1978 homes may meet the specific criteria for not being “substantially improved12;” therefore, a waiver request from this provision is included in Section 5.3 below. 12 “Substantially Improved” is defined in Section 1.02 of the local wetlands regulations as: “cumulative expansion of habitable space greater than twenty percent (20%).” “Habitable Space” is defined in Section 1.02 of the local wetlands regulations as: “space in a structure for living, sleeping, eating or cooking. Bathrooms, toilet compartments, closets, halls, storage or utility space, and similar areas are not considered habitable space.” 21597/Sconset/NOI 5-13 Regulatory Consistency Epsilon Associates, Inc. ♦ Alternatives: The Alternatives Analyses described in Section 3.5 demonstrate that although numerous alternatives have been considered and evaluated (or even implemented previously in the Project area), no suitable alternatives to the proposed Project exist which would satisfy the objective of providing long-term protection for existing structures that pre-date September 1978 and have not been substantially improved and that are in imminent and ongoing danger from the demonstrated erosion of the bank. Section 2.02 B(4) - Performance Standard “Clean fill of a compatible grain size may be used on a Coastal Beach, but not on a Tidal Flat, only if the Commission authorizes its use, and only if such fill is to be used for a beach or dune nourishment project. All possible mitigation measures shall be taken, as determined by the Commission, to limit the adverse effects of the fill.” Project Compliance: Project compliance with this standard is discussed below. ♦ Clean Fill: Sand mitigation will consist of placing clean, beach-compatible sand into the littoral system. ♦ Tidal Flats: The Project does not involve placement of sand on any tidal flats. Section 2.02 B(9) – Performance Standard “The Commission may impose such additional requirements as are necessary to protect the Interests Protected by the Bylaw.” Project Compliance: The Project has been designed using best available measures to stabilize the coastal bank and protect existing landward structures and public infrastructure while simultaneously avoiding, minimizing, and mitigating for potential impacts. All of the interests protected by the Bylaw have been considered during the process of Project design. Nantucket Land Subject to Coastal Storm Flowage (Section 2.10) “Land Subject to Coastal Storm Flowage” is defined in Section 1.02 of the local wetlands regulations as “land subject to any inundation caused by coastal storms up to and including that caused by the 100-year storm, surge of record, or storm of record, whichever is greater.” Performance Standards for Land Subject to Coastal Storm Flowage (LSCSF) are defined in Section 2.10 of the local wetlands regulations, which provides that “Land Subject to Coastal Storm Flowage or Land within 100 feet of Land Subject to Coastal Storm Flowage shall be presumed significant to the interests Protected by the Bylaw, as referenced in Section A, therefore the following regulations shall apply:” 21597/Sconset/NOI 5-14 Regulatory Consistency Epsilon Associates, Inc. The Project does not include activities or structures subject to the following performance standards, and hence they are excluded from the subsequent discussion: ♦ Section 2.10 B(2) (use of pollutants or septic systems); ♦ Section 2.10 B(3) (underground fuel tanks); and ♦ Section 2.10 B(4) (new buildings). The applicable Sections 2.10 B(1) and 2.10 B(5) are discussed below. Section 2.10 B(1) – Performance Standard “The work shall not reduce the ability of the land to absorb and contain flood waters, or to buffer inland areas from flooding and wave damage.” Project Compliance: The Project will not reduce the ability of LSCSF to absorb and contain flood waters. By stabilizing the bank face and providing protection at the toe of bank, the Project will enhance the coastal bank’s function of buffering inland areas and buildings from storm damage. Section 2.10 B(5) “The Commission may impose such additional requirements as are necessary to protect the Interests Protected by the Bylaw.” Project Compliance: The Project has been designed using best available measures to stabilize the coastal bank and protect existing landward structures while simultaneously avoiding, minimizing, and mitigating for potential impacts. All of the interests protected by the Bylaw have been considered during the process of Project design. 5.3 Waiver Request The Applicants request a waiver from the following local performance standard for Coastal Beaches and/or Coastal Banks. ♦ Section 2.01 B(7), 2.02 B(2), and 2.05 B(1): Not every pre-1978 structure in the project area (on both the landward and seaward sides of Baxter Road) may meet the definition of not “substantially improved”13; therefore, a request to waive 13 The pre-1978 house status of the homes in the project area is presented on Figure 9. In 310 CMR 10.30 it is provided that coastal engineering structures “shall be permitted” to protect pre-1978 homes. DEP expressly finds that the project is within the scope of that provision. There is a parallel provision in the Nantucket Wetlands Regulations. We note the “20% change” language incorporated into certain aspects of the portions of the Nantucket Wetlands Regulations which address pre-1978 structures. That language does not of course apply to infrastructure. Nothing in this request is, or is intended to be, a waiver, admission, or acknowledgement adversely affecting any claim or argument available to SBPF that a municipality has jurisdiction or authority to impose more stringent limitations on projects that “shall be 21597/Sconset/NOI 5-15 Regulatory Consistency Epsilon Associates, Inc. Section 2.02 B(2), and Section 2.01 B(7) and 2.05 B(1), as appropriate, is hereby made in connection with the proposed construction of the geotextile tubes placed beneath or on top of the landward end of the coastal beach. ♦ The Applicants also request any other waiver that the Commission deems appropriate.14 The basis for each of the requested waivers is that, given existing conditions, the Project will not adversely impact the interests identified in the By-law. The Project incorporates regular monitoring, mitigation, and reporting that will allow the Commission to carefully review the Project through time. Further, there is an ongoing threat from erosion to both public infrastructure and pre-1978 structures, and there are no reasonable conditions or alternatives that would allow the Project to proceed in compliance with the regulations. permitted” under the Wetlands Protection Act Regulations than those provided for in those Regulations. SBPF expressly reserves all of its rights with respect thereto. 14 The September 2015 Order of Conditions for the Existing Project also included waivers from Section 2.01 B(8), 2.05 B(3), and 2.10 B(1). Attachment B Figures Copyright:© 2013 National Geographic Society, i-cubed G:\Projects\Lighthouse\2013\NOI\usgs.mxd Figure 1USGS Locus Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA LEGEND Basemap: 1972 USGS Quadrangles, ESRI Existing Project Lots Expanded Project Lots Property Boundary °0 500 1,000250Feet1 inch = 1,000 feetScale1:12,000 Project Area59-119 Baxter Road BAXT ER ROADSANKATY ROADI SABEL L E'S WAYISOBELS WAYSANKATY HEAD ROADPOLPIS ROAD BAYBERRY LANE 99 97 87 101 105 93 91 85 73 83 109 81 79 77 117 75 115 113 119 107 107A 53 51B 55 51A 63 59 69 61 71 67 65 Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS,AeroGRID, IGN, and the GIS User Community G:\Projects\Lighthouse\2013\NOI\aerial.mxd Figure 2Aerial Locus Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA LEGENDExisting Project Lots Expanded Project Lots Property Boundary Basemap: 2016 Aerial Imagery, ESRI °0 150 30075Feet1 inch = 300 feetScale1:3,600 Figure 3 August 2017 Existing Conditions South of Lot 61 Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA Figure 4 August 2017 Existing Conditions Lots 59 to 65 63 Baxter 59 Baxter 65 Baxter Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA Figure 5 August 2017 Existing Conditions Lots 63 to 79 Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA 71 Baxter 73 Baxter 75 Baxter 77 Baxter 79 Baxter Figure 6 August 2017 Existing Conditions Lots 73 Northward Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA Figure 7 August 2017 Existing Conditions Lots 85 to 105 Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA Figure 8 August 2017 Existing Conditions Lots 93 to 115 109 Baxter 113 Baxter 115 Baxter Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA BAXT ER ROADSANKATY ROADI SABEL L E'S WAYISOBELS WAYSANKATY HEAD ROADPOLPIS ROAD BAYBERRY LANE 53 52 86 63 97 51B 73 83 59 92 68 82 109 106 6970 100 81 79 61 55 104 51A 71 93 84 67 77 75 115 96 65 113 116 58 112 72 85 99 87 101 105 91 117 80 119 107 107A 64 60 54 3 54A 56 76 94 62 108 110 90 120 78 114 98 82A Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS,AeroGRID, IGN, and the GIS User Community G:\Projects\Lighthouse\2013\NOI\year_built.mxd Figure 9Pre-1978 House Status Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA LEGEND Basemap: 2016 Aerial Imagery, ESRI Pre-1978 House Status Pre-1978 Post-1978 Vacant Not Specified °0 150 30075Feet1 inch = 300 feetScale1:3,600 BAXT ER ROADSANKATY ROADI SABEL L E'S WAYISOBELS WAYSANKATY HEAD ROADPOLPIS ROAD BAYBERRY LANE 85 73 83 109 81 79 77 117 75 115 113 119 107 107A 63 59 69 61 71 67 65 53 51B 55 51A 99 97 87 101 105 93 91 Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS,AeroGRID, IGN, and the GIS User Community G:\Projects\Lighthouse\2013\NOI\wetlands.mxd Figure 10Wetland Resource Areas Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MACOASTAL BEACHCOASTAL BEACHCOASTAL BEACHCOASTAL BEACHLEGEND Basemap: 2016 Aerial Imagery, ESRI Existing Project Lots Expanded Project Lots Property Boundary 100-foot Buffer Coastal Dune Coastal Bank °0 150 30075Feet1 inch = 300 feetScale1:3,600 BAXT ER ROADSANKATY ROADI SABEL L E'S WAYISOBELS WAYSANKATY HEAD ROADPOLPIS ROAD BAYBERRY LANE 85 73 83 109 81 79 77 117 75 115 113 119 107 107A 63 59 69 61 71 67 65 53 51B 55 51A 99 97 87 101 105 93 91 Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS,AeroGRID, IGN, and the GIS User Community G:\Projects\Lighthouse\2013\NOI\fema.mxd Figure 11FEMA Q3 Flood Zones Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA LEGEND Basemap: 2016 Aerial Imagery, ESRI Existing Project Lots Expanded Project Lots Property Boundary Flood Zone VE: 100-year Flooding °0 150 30075Feet1 inch = 300 feetScale1:3,600 Figure 12 August 2017 Existing Conditions –Coastal Dune and Coastal Bank Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA BAXTER ROADSANKATY ROADISABE L LE 'S WAY ISOBELS WAYSANKATY HEAD ROADPOL P I S R O A D BAYBERRY LANE 85 73 83 109 81 79 77 117 75 115 113 119 107 107A 99 97 87 101 105 93 91 63 59 69 61 71 67 65 53 51B 55 51A Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS,AeroGRID, IGN, and the GIS User Community G:\Projects\Lighthouse\2013\NOI\aerial.mxd Figure 13NHESP Habitat Map Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA LEGENDExisting Project Lots Expanded Project Lots Property Boundary NHESP 2017 Priority Habitats for State-Protected Rare Species NHESP 2017 Estimated Habitats for Rare Wildlife Basemap: 2016 Aerial Imagery, ESRI °0 300 600150Feet1 inch = 300 feetScale1:3,600 Figure 14 June 2017 Image of Vegetation in Existing Geotextile Tube Project Area Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA S1 Q1 Q2 S Q 81 83 84 85 82 86 87 88 89 90 91 92 93 94 95 96 9798 99 W Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community G:\Projects\Lighthouse\2017\MXD\Transects_Overview_20180102.mxd Figure 15Shoreline Monitoring Survey Transects - Wauwinet to Sewer Beds Expanded Baxter Road and Sconset Bluff Stabilization Project Nantucket, Massachusetts LEGEND Project Area Properties WHG Survey Line WAUWINET SEWER BEDS SQUAM QUIDNET SIASCONSET SesachachaPond AtlanticOcean LIGHTHOUSE see Figure 16for zoom-in toProject Area Basemap: 2016 Aerial Imagery, ESRI °0 1,100 2,200550 Feet1 inch = 2,200 feet Scale 1:26,400 BAXTER ROADSANKATY ROADSANKATY HEAD ROADISABELLE'S WAYPOL P I S R O A D ISOBELS WAY ANNES LANE BAYBERRY LANE ELDRIDGE LANE 90.8 90.9 91.2 91.9 92.2 92.1 91.35 90.85 90.95 88 89 9091 93 94 88.6 89.2 89.8 89.5 90.6 91.5 92.5 93.5 53 63 51B 59 69 61 55 71 51A 67 65 85 99 97 87 73 83 101 105 109 81 79 93 91 77 117 75 115 113 119 107 107A 92 Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community G:\Projects\Lighthouse\2017\MXD\WHG_Project_Area_20180102.mxd Figure 16Shoreline Monitoring Survey Transects - Project Area Expanded Baxter Road and Sconset Bluff Stabilization Project Nantucket, Massachusetts LEGEND Property Boundaries WHG Survey Line Basemap: 2016 Aerial Imagery, ESRI °0 200 400100 Feet1 inch = 400 feet Scale 1:4,800 Attachment C Project Plans PREPARED FOR:12716 - C - 0002924 MARKETPLACE DRIVE, SUITE 200MADISON, WI USA 53719W.F. Baird & AssociatesCoastal Engineers Ltd.PREPARED BY:PROJECTLOCATIONMARTHA'SVINEYARDATLANTICOCEANNANTUCKETN.T.SN.T.SPROVIDENCENEWBEDFORDATLANTICOCEANPURPOSE: BLUFF STABILIZATIONDATUM: NAD83EXPANDED BAXTER ROAD ANDSCONSET BLUFF STORM DAMAGEPREVENTION PROJECTSCONSET BEACHCOUNTY OF NANTUCKETSTATE OF MASSACHUSETTSPO BOX 2279NANTUCKET, MA 02554ADJACENT PROPERTY OWNERS: SEE APPLICATIONAGENT: EPSILON ASSOCIATES, INC.DATE: 2018-01-04SHEET 1 OF 6VICINITY MAPFOR PERMIT USE ONLYNOT FOR CONSTRUCTIONPROJECTLIMITSSIASCONSET -2502550 -2502 5 50 0 2 5 507 5 -250 255 0 7 51005558566463718659606261656867697072376737875807779828182A84838590879299 114113919493969897100104101106105107108107A110109112116115117120119REVISIONSREV(T.I.)T.I.TYPE OFISSUEDESCRIPTIONDRNDSNAPRYYYY-MM-DDREV.PREPARED FOR:1/4/2018 3:59:38 PMDate Plotted:P:\12643.101 SCONSET BEACH PRESERVATION FUND\H - CADD\WORKING DRAWINGS\C PERMIT\12643-C-010.DWG DRAWING NUMBER:DATE:PREPARED BY:W.F. Baird & Associates Ltd.(A) INFORMATION(B) REVIEW(D) TENDER DOCUMENT(F) RECORD(E) CONSTRUCTION DOCUMENT(C) PERMITSCONSET BEACH PRESERVATION FUNDEXISTING CONDITIONS12643C010A2018-01-04ACFOR PERMITBKCLMAGCT2018-01-04GRAPHIC SCALE FEET0500250125NORTHGENERAL NOTES1.CONTOURS ARE DERIVED FROM THE 2017 LIDAR SURVEY AND THE FALL 2016 WOODS HOLE TOPO ANDBATHYMETRY SURVEY.2.ELEVATIONS ARE IN FEET AND ARE REFERENCED TO MLW '92.3.GEOTUBES TO BE FIELD FIT TO MINIMIZE EXCAVATION.TN-1TN-2122TN-3 -2502550 -25 0 2 5 5 0 0 2 5 507 5 -25 0 255 0 7 51005558566463718659606261656867697072376737875807779828182A84838590879299 114113919493969897100104101106105107108107A110109112116115117120119REVISIONSREV(T.I.)T.I.TYPE OFISSUEDESCRIPTIONDRNDSNAPRYYYY-MM-DDREV.PREPARED FOR:1/4/2018 4:00:14 PMDate Plotted:P:\12643.101 SCONSET BEACH PRESERVATION FUND\H - CADD\WORKING DRAWINGS\C PERMIT\12643-C-010.DWG DRAWING NUMBER:DATE:PREPARED BY:W.F. Baird & Associates Ltd.(A) INFORMATION(B) REVIEW(D) TENDER DOCUMENT(F) RECORD(E) CONSTRUCTION DOCUMENT(C) PERMITSCONSET BEACH PRESERVATION FUNDPROPOSED PLANVIEW12643C020A2018-01-04ACFOR PERMITBKCLMAGCT2018-01-04FOUR SAND FILLED 45'CIRCUMFERENCE GEOTUBES (TYP.)GEOTUBE RETURNTOP OF HIGHEST BAGEL. - +25.0GEOTUBE RETURNTOP OF HIGHEST BAGEL. - +25.0EXISTING JUTE AND COIRTEMPORARY STRUCTURETO BE REMOVED.EXISTING GEOTUBEEXACT LOCATION ANDELEVATIONS TO BE VERIFIEDTIE IN TO EXISTING GEOTUBESAS DIRECTED TO SITE ENGINEERGEOTUBE #4CREST EL. - +25.0'GEOTUBE #3CREST EL. - +18.0'GEOTUBE #2CREST EL. - +11.0'GEOTUBE #1CREST EL. - +4.0'FOUR SAND FILLED 45'CIRCUMFERENCE GEOTUBES (TYP.)4 - SAND FILLED 45'CIRCUMFERENCE GEOTUBES (TYP.)TIE IN TO EXISTING GEOTUBESAS DIRECTED BY SITE ENGINEERGRAPHIC SCALE FEET0500250125ANCHOR TUBE(TYP.)NORTH04001040020400304004TOP OF WATER TRENCH (± +5.0)BOTTOM OF WATERTRENCH (± -3.0)GENERAL NOTES1.CONTOURS ARE DERIVED FROM THE 2017 LIDAR SURVEY AND THE FALL 2016 WOODS HOLE TOPO ANDBATHYMETRY SURVEY.2.ELEVATIONS ARE IN FEET AND ARE REFERENCED TO MLW '92.3.GEOTUBES TO BE FIELD FIT TO MINIMIZE EXCAVATION.TN-1TN-2122TN-3 REVISIONSREV(T.I.)T.I.TYPE OFISSUEDESCRIPTIONDRNDSNAPRYYYY-MM-DDREV.PREPARED FOR:1/4/2018 3:43:12 PMDate Plotted:P:\12643.101 SCONSET BEACH PRESERVATION FUND\H - CADD\WORKING DRAWINGS\C PERMIT\12643-C-010-NO GEO.DWG DRAWING NUMBER:DATE:PREPARED BY:W.F. Baird & Associates Ltd.(A) INFORMATION(B) REVIEW(D) TENDER DOCUMENT(F) RECORD(E) CONSTRUCTION DOCUMENT(C) PERMITSCONSET BEACH PRESERVATION FUNDPROPOSED PLANVIEW12643C030A2018-01-04ACFOR PERMITBKCLMAGCT2018-01-04GRAPHIC SCALE FEET0500250125NORTH05005050060500705008GENERAL NOTESSAND TEMPLATE CRESTTOE OF SAND TEMPLATESAND TEMPLATE CRESTTOE OF SAND TEMPLATEAPPROXIMATE SAND TEMPLATEINTERCEPT WITH BLUFFEXISTING JUTE AND COIRTEMPORARY STRUCTURETO BE REMOVED.EXISTING GEOTUBEEXACT LOCATION ANDELEVATIONS TO BE VERIFIED1.CONTOURS ARE DERIVED FROM THE 2017 LIDAR SURVEY AND THE FALL 2016 WOODS HOLE TOPO ANDBATHYMETRY SURVEY.2.ELEVATIONS ARE IN FEET AND ARE REFERENCED TO MLW '92.APPROXIMATE SAND TEMPLATEINTERCEPT WITH BLUFF REVISIONSREV(T.I.)T.I.TYPE OFISSUEDESCRIPTIONDRNDSNAPRYYYY-MM-DDREV.PREPARED FOR:1/4/2018 3:42:16 PMDate Plotted:P:\12643.101 SCONSET BEACH PRESERVATION FUND\H - CADD\WORKING DRAWINGS\C PERMIT\12643-C-010.DWG DRAWING NUMBER:DATE:PREPARED BY:W.F. Baird & Associates Ltd.(A) INFORMATION(B) REVIEW(D) TENDER DOCUMENT(F) RECORD(E) CONSTRUCTION DOCUMENT(C) PERMITSCONSET BEACH PRESERVATION FUNDTYPICAL SECTIONS12643C040A2018-01-04ACFOR PERMITBKCLMAGCT2018-01-04GRAPHIC SCALE FEET0502512.502TYPICAL GEOTUBE SECTION040ANCHOR TUBEEXISTINGGRADEFOUR SAND FILLED 45'CIRCUMFERENCE GEOTUBES (TYP.)-3.0+4.0+11.0+18.0+25.019' ±7.0' ±7.5' ±GEOTEXTILE100 YR STORM W.L (+7.68)5.0'PROPOSED SAND TEMPLATE5.0'+5.05.0' ±7.5' ±01TYPICAL GEOTUBE SECTION04003TYPICAL GEOTUBE SECTION04004TYPICAL GEOTUBE SECTION04021GENERAL NOTES1.ELEVATIONS ARE REFERENCED TO MLW '92.2017 (WOODS HOLE LIDAR)2017 (WOODS HOLE LIDAR)2017 (WOODS HOLE LIDAR)2017 (WOODS HOLE LIDAR)100 YR STORM W.L (+7.68)100 YR STORM W.L (+7.68)100 YR STORM W.L (+7.68)WATERTRENCH AREA2.0'2.0'2.0'2.0' REVISIONSREV(T.I.)T.I.TYPE OFISSUEDESCRIPTIONDRNDSNAPRYYYY-MM-DDREV.PREPARED FOR:1/4/2018 3:44:27 PMDate Plotted:P:\12643.101 SCONSET BEACH PRESERVATION FUND\H - CADD\WORKING DRAWINGS\C PERMIT\12643-C-010-NO GEO.DWG DRAWING NUMBER:DATE:PREPARED BY:W.F. Baird & Associates Ltd.(A) INFORMATION(B) REVIEW(D) TENDER DOCUMENT(F) RECORD(E) CONSTRUCTION DOCUMENT(C) PERMITSCONSET BEACH PRESERVATION FUNDTYPICAL SECTIONS - SAND TEMPLATE12643C050A2018-01-04ACFOR PERMITBKCLMAGCT2018-01-04GRAPHIC SCALE FEET0502512.5+30 ±100 YR STORM W.L (+7.68)SAND TEMPLATE CREST05TYPICAL SAND TEMPLATE SECTION050GENERAL NOTES1.ELEVATIONS ARE REFERENCED TO MLW '92.2017 (WOODS HOLE LIDAR)100 YR STORM W.L (+7.68)100 YR STORM W.L (+7.68)100 YR STORM W.L (+7.68)TOE OF SAND TEMPLATESAND TEMPLATE INTERCEPT WITH BLUFF+30 ±SAND TEMPLATE CREST2017 (WOODS HOLE LIDAR)TOE OF SAND TEMPLATESAND TEMPLATE INTERCEPT WITH BLUFF+30 ±SAND TEMPLATE CREST2017 (WOODS HOLE LIDAR)TOE OF SAND TEMPLATESAND TEMPLATE INTERCEPT WITH BLUFF+30 ±SAND TEMPLATE CREST2017 (WOODS HOLE LIDAR)TOE OF SAND TEMPLATESAND TEMPLATE INTERCEPT WITH BLUFF07TYPICAL SAND TEMPLATE SECTION05008TYPICAL SAND TEMPLATE SECTION05006TYPICAL SAND TEMPLATE SECTION050 Attachment D Construction Dates of Baxter Road Properties Construction Dates of Baxter Road Properties 51 – 120 Baxter Road Property Owner Property Address Map/ Parcel Date of Initial Construction of Main Dwelling (& Cottages/Garages as Noted); references to other outbuildings are only noted if they were referenced in HDC files Alterations, etc. per Building Dept. Records & Moves per Building Dept. Records and Historic Structures Files Note: year noted is year applied/permit issued Richard S. and Linda M. Mackay 120 Baxter Road 48-33 House: 1983 1983 – Single family dwelling Sconset Trust, Inc. 119 Baxter Road 48-7 1987 – Moved to 82 Baxter Road Stephen B. Cohen 117 Baxter Road 48-9 House: By 1923/ 1978 Garage: By 1923 1978 – Single family dwelling 1988 – Moved on same lot 2001 – New deck piers & rails (issued?) 2005 – Moved to 116 Baxter Road Stephen B. Cohen 116 Baxter Road 48-34 2005 – 117 Baxter moved to this lot 2012 – Replace windows, rakes, fascia, soffit, gutters & cornerboards Donald E. Claudy, Trustee 115 Baxter Road 48-10 House: By 1923/ 1925 1983 – Structural repairs, new deck, interior reno 1987 – Alter and renovate, raise roof, new windows & doors 1988 – 2nd floor addition, window & door changes 1988 – Relocate house on same lot, add steps - sewer Rick Hinchey, Trustee 114 Baxter Road 48-35 House: 1984 1984 – Dwelling 1998 – Repair & replace 8 windows Kyle L. Latshaw and Loretta A. Yoder 113 Baxter Road 48-11 House: Since 1940 1988 – Move on same lot Ann B. Furrow 112 Baxter Road 48-36 2005 – 99 Baxter moved to this lot, add basement 1494 sf finished space, 1st floor add 314 sf, 2nd floor existing, 5 beds/5 baths Patrick T. Ryan, Trustee 110 Baxter Road 48-37 House: 2001 2nd Dwelling: 2005 2001 – 2 story, 4 bed, 4 bath dwelling – septic 2005 – Construct 1 DU; 1st floor 615 sf – 2nd dwelling 2006 – Finish basement 550 sf John P. and Susan D. Deangelis 109 Baxter Road 48-12 Since 1940 1988 – Moved from “Lot A to Lot B”/111 Baxter Road (109 & 111 are combined) 1988 – Alter and repair dwelling 1996 – Renovate 1st 1012 sf, basement 980 sf, rec room, bath, storage, add 450 sf 2nd 2 br, bath, 1 du (note: plans show new dormers, replace windows, new porch, etc.) Whitney A. Gifford, Trustee 108 Baxter Road 48-38.1 House: 2001 2nd Dwelling: 2005 2001 – Build 2 story 4 br 1 du 2005 – Construct 1 du finished full cellar (2nd dwelling) Whitney A. Gifford, Trustee 107A Baxter Road 48-14 Whitney A. Gifford, Trustee 107 Baxter Road 48- 14.1 William B. & Marilee B. Matteson 106 Baxter Road 48-39 Garage by 1940 1998 – 105 Baxter moved to this lot 2004 – pool w/fence 2004 – renovate garage William B. & Marilee B. Matteson 105 Baxter Road 48-15 By 1940 1975 – Moved per HDC file 1988 – Moved on same lot; add & alter (per plans, alterations appear to be new decks and lattice at large deck) 1998 – Moved to 106 Baxter James E. Walker, III and Deborah C. Walker 104 Baxter Road 48-40 2001 – 101 Baxter moved to this lot; necessary repairs and maintenance 2007 – Cover existing deck w/porch roof 2011 – Enclose porches 1st & 2nd floor, add bath . . . James E. Walker, III and Deborah C. Walker 101 Baxter Road 48-17 By 1940 1984 – Permit noted on file cover, but permit is not in file (work performed is not indicated) 1988 – Moved per HDC file 1989 – “Move” noted on file cover, but permit is not in file 2001 – Emergency move to 104 Baxter David S. and Dorothy O. Bailey 100 Baxter Road 48-42 House: 1983 Garage Apt.: 2004 Shed: Since 1940 1983 – Construct 2 story, 4 bedroom single family dwelling, deck 2004 – Relocate dwelling and 1 story addition – sewer on same lot 2004 – 2 story 1 br 1 bath garage apt. Ann B. Furrow 99 Baxter Road 48-18 House: By 1940 Garage: Since 1940 1975 – Moved per HDC file 1988 – Moved on same lot 1999 – Renovate entire DU (no exterior changes per application) 2005 – Moved to 112 Baxter Road 2010 – Move 400 sf storage shed onto lot from 97 Baxter and place on slab foundation – no plumbing 2013 – Emergency demolition of garage due to coastal erosion Janice S. Savery et al. 98 Baxter Road 48-43 House: 1980 1980 – 1 story 2 BR, 2 Bath DU – sewer 2005 – Renovate kitchen 160 sf, renovate baths 112 sf & replace front door w/like kind 2006 – Porch roof and outside shower stall 2006 – Demo shed 2006 – Construct shed Lawrence C. and Margaret McQuade 97 Baxter Road 48-19 House and Guesthouse: Since 1940 Garage: 1982 1972 - Addition 1975 – Moved per HDC file 1982 – Garage 1982 – Addition (enlarge one room, enclose porch) 1988 – Moved on same lot 1988 – Move garage 1989 – Addition 1996 – Renovate 2nd floor bath & deck and mudroom additions 1998 – Add 839 sf unfinished 2nd floor to 3 br 1 du, 297 sf 1st addition, reno 160 sf kitchen area 2005 – demo 24’ x 16’ section of studio due to bank erosion 2010 – Move 400 sf storage building off lot to 99 Baxter 2010 – Moved part to 7 Plainfield leaving 720 sf portion for conversion to 1 DU 2010 – Convert & relocate existing remaining elements per plans for new 1 DU . . . Alexander Webb, III and Laura R. Webb 96 Baxter Road 48-44 House and Guesthouse Since 1940 2007 – Replace windows & doors, extend deck 8’ x 12’, arbor at front door Daniel T. Korengold, Trustee 94 Baxter Road 48-45 Steven T. and Erin P. Freeman 93 Baxter Road 48-21 House: 1950/1951 Garage Apt.: ND 1992 – Relocate garage on same lot 1992 – Relocate 1 DU on same lot 2005 – Renovate 140 sf kitchen, 2 full baths 100 sf, new walls living room & new floor in family room “interior only” 2010 – Relocate dwelling on same lot 2010 – Relocate garage on same lot Daniel T. Korengold, Trustee 92 Baxter Road 48-23 House and Shed: Since 1940 New Dwelling and Garage/Studio: 2005 2005 – Demo garage 2005 – Move 1 DU 1133 sf dwelling to 18 Irving 2005 – Construct garage w/studio 2005 – Construct new dwelling full cellar finished Daniel T. Korengold, Trustee 91 Baxter Road 48-22 Laurance J. Guido, MD FACS et al. 90 Baxter Road 49-5 House: 1996 1996 - Dwelling Samuel and Ann Furrow 87 Baxter Road 49-8 House: 1976 1976 – One family dwelling 1988 – Add and alter dwelling 1988 – Enclose existing porch 1989 – Add 192 sf and alter 972 sf to existing dwelling 1990 – alterations (“interior change”) 2003 – renovate kitchen 1st floor & renovate 2nd fl master bedroom and bath area, shingle roof) 2007 – relocate 1 DU on same lot on 5 ft crawl space 2013 – Demolish 2 story single family dwelling . . . Clark M. Whittemore, Jr., Trustee 86 Baxter Road 49-36 House: By 1940 Garage: 1983 1983 – Garage 1995 – 16’ x 17’ deck 1996 – Add 2nd floor br & bath 2002 - Shed Jay W. Wertheimer, Trustee 85 Baxter Road 49-35 House: 1925/By 1940 Guesthouse: Since 1975 Garage: Since 1940 2006 – Demo existing 748 sf dwelling 2010 – Prepare dwelling to move off lot; amended to reflect move off of primary structure to 47 Monomoy 2010 – Prepare dwelling for move off lot . . . (cottage) 2011 – Demo garage (amended to move off) Note: other permit numbers are noted on face of file, but are not inside file Juliet F. Hunter, Trustee 84 Baxter Road 49-37 House and Garage: Since 1940 1991 – Kitchen and bedroom addition Marie Dostalier et al. 83 Baxter Road 49-34 House: Since 1940 1982 – Extension of existing kitchen 1991 – Addition of sunroom and roof over dining room 2001 – Relocate dwelling and place on new foundation on same lot East Eden, LLC 82A Baxter Road 49-38 House: 1993 1993 – 2 story 2 bedroom single family dwelling 1996 – bed, bath & shed addition 82 Baxter Road, LLC 82 Baxter Road 49-39 House: By 1923 1987 – 119 Baxter moved to this lot (& build deck per application) William D. and Deborah F. Cohan 81 Baxter Road 49-33 House: By 1923 New House: 1994 1993 – Demolish 1393 sf 1 story 3 br 1 du 1993 – 2 story, 4 bedroom single family dwelling 2001 – addition to dwelling, add deck, renovate 1st floor Joshua Posner and Eileen Rudden 80 Baxter Road 49-40 Helmut F. and Caroline S. Weymar 79 Baxter Road 49-23 House: 1916/By 1923 Shed: ND Per HDC file: 1987-1988 North Wing, Porch, Deck Roof Walk Reconstructed 1989 – Demo shed 1989 – Alter & add to single family dwelling 1997 – Add 278 sf to 1st floor deck 1 du 1999 – Replace windows, redo roofwalk Caroline S. Weymar, Trustee 78 Baxter Road 49-41 House: 1990 1990 – 2 bedroom single family dwelling 1993 – 16’ x 16’ deck to rear of 1 du 1994 – Change 2nd floor to 3 br’s – 4 br total 1 du 2002 – Construct 100 sf addition along/w 3 shed dormers Joshua Posner and Eileen Rudden 77 Baxter Road 49-31 House: Since 1940 Shed: ND 2005 – Demo 558 sf bunkhouse 2006 – Move existing house on same lot, add finished full basement, add sunroom & garage Caroline S. Weymar, Trustee 76 Baxter Road 49-42 Combined w/3 Bayberry Lane b dept. file Sankaty Bluff Group, LLC 75 Baxter Road 49-30 House: 1922/ By 1923 Garage: By 1923 2002 – Add dormer, add 2 decks, reno interior 2004 – Add dormer & windows to existing garage, replace garage doors, add storage loft, construct pergola Linda Mason, Trustee 3 Bayberry Lane 49-43 1991 – Renovate 3 br 1 du both floors, doors & windows 1992 – add 238 sf br over porch, deck 1 du 1992 – Renovate garage to living space Joan R. Brecher et al. 73 Baxter Road 49-27 House: 1920 Garage: ND 1986 – Addition of 2nd story bathroom 1989 – Construct addition 1989 – Build 10’ x 14’ addition to garage for storage 2012 – Demolish 350 sf of 1st floor, relocate on same lot, add 150 sf 1st kitchen, reno baths, reside wall & roof James K. McAuliffe, Trustee 72 Baxter Road 49-44 House: Since 1940 Garage: 1993 1993 – Total renovation of single family dwelling 1993 – Construct garage 1996 – Renovate and convert garage to heated studio w/bath 1998 – Build one story addition for a master bathroom 2008 – Pool 2008 – Construct cellar under studio, remove non-conforming shed, relocate entry door 2012 - Shed John C. Merson and Carol Bunevich 71 Baxter Road 49-26.1 House: 1932/ 1939 Garage: 1932 1982 – Bedroom addition 2004 – Repair/replace walls, reno bath (interior only) 2005 – Construct deck at east entrance & outside shower 2009 – Dismantel cottage/garage 2009 – Relocate 1 du on same lot, remove additions, construct finished full cellar, reno 1st flr 1500 sf & add 2nd fl 400 sf Susan Wilner and David Golden, Trustees 70 Baxter Road 49-45 House: 1940 New House and Garage Studio: 2000 Guesthouse: Since 1940 1989 – Alter interior/add windows & deck 2000 – Build a 2 story 4 br 1 du 2000 – Garage studio 2000 – Move 1 du 1740 sf to 4 Lincoln St. 2000 – Move 1 du off to 4 Lincoln St., 1200 sf Richard and Marianne L. Moscicki 69 Baxter Road 49-25 Dwelling & Garage Apt.: Since 1940 New House: 1996 1996 – Build 2 story 5 br 1 du 1920 sf 1st 1830 sf 2nd 1997 – Move garage to 320R Milestone 1997 – Move house to 320R Milestone 1999 – Add wet bar and powder room in basement Whitney A. Gifford, Trustee 68 Baxter Road 49-47 House: By 1938 1996 – Add 5068 frenchwood door and window side of 1 du & amendment to remove existing wall, replace ceiling and floor, install 6’0” x 6’8” patio door 2004 – Renovate 1st and 2nd floor, add 2nd floor Morning Light, LLC 67 Baxter Road 49-24 House: 1930; Garage: ND 1979 – Construct 5’6” x 9’ and 5’6” x 16’ additions 2001 – Relocate DU on same lot for setback compliance 2002 – Repairs and reshingle side & roof, red fire proof shingles on roof (note: it looks like this is permit is for the garage) 2002 – Reno of relocated DU, 2 new decks – sewer; add porch & 2nd floor deck Thomas and Sharmila Tuttle 65 Baxter Road 49-23 House: 1895; Garage & Shed: ND 2001 – Raise house to provide cellar, completely renovate 3 story 1 DU 2001 – Reno shed 2001 – Reno garage Elizabeth Singer 64 Baxter Road 49-51 2006 – Shed NOTE: GIS shows tennis court on property Elizabeth Singer 63 Baxter Road 49-22 House: 1890/ 1892 Garage Apt.: By 1923 (was a stable) 2nd Dwelling: 2004 Garage and Store 2002 – Reno existing dwelling unit approx.. 3000 sf reroof & shingle walls 2004 – Demo guest house/garage 2004 – 2nd dwelling 2005 – Demo shed 2007 – Garage and store room Room: 2007 Shed: By 1923 Ann R. Healey, Trustee et al. 62 Baxter Road 49-52 Ann R. Healey, Trustee et al. 61 Baxter Road 49-21 House: 1893-4/1893 Beach house: ND Garage: By 1923 2004 – Repair existing porch decking & joists – reroof 2800 sf trim 1 du & amendment to reshingle, renovate kit, laundry & 4 baths, foundation repairs, 1st flr girder replacement, insulate & add heat, upgrade plumbing & electrical ABCET, LLC 60 Baxter Road 49-53 Kevin F. Dale, Trustee 59 Baxter Road 49-20 House: 1905/ By 1923 Shed: ND Garage/Workshop: 1996 1991 – Rebuild shed 1991 – Rebuild front porch, alter windows & doors, reside & reroof & amendment to add 121 sf porch enclosure, bed, bath 1996 – Build garage/workshop 1999 – Remove enclosure on 166 sf porch – add steps and door 2003 – Replace fixtures & tile in 3 baths 2011 – Raise dwelling & place on new full foundation; finish basement BR, 2 BA, LR; reno 495 sf, add 97 sf 1st, reno 153 sf 2nd ABCET, LLC 58 Baxter Road 49-54 House: Since 1938 1987 – Install new bath fixtures & kitchen facilities (“garage to dwelling” per file cover) 1999 – Relocate on same lot, demo part & add 1 story 1 du 1138 sf 680 sf habitable basement ABCET, LLC 56 Baxter Road 49-55 Stephen W. Kidder, Trustee, et al. 55 Baxter Road 49-18 House: 1890 1973 – Addition (library) 1998 – Relocate dwelling on same lot, new finished cellar, renovate remaining 2 stories - porch ABCET, LLC 54A Baxter Road 49-122 ABCET, LLC 54 Baxter Road 49-125 Stephen W. Kidder, Trustee, et al. 53 Baxter Road 49-17 House: 1925/ 1930 Garage: 1930 1987 – Addition to garage 1987 – 850 sf addition 1988 – 16 ½ sf addition 1997 – Repair & replace chimney 2000 – Replace windows & doors on 1 du 2007 – Renovate kitchen, bath & office 800 sf on 2nd fl renovate 3 bathrooms 350 sf 2011 – Remove existing beach stairs and rebuild new deck and stairs 52 Baxter Road, LLC 52 Baxter Road 49-57 House: Since 1938 1988 - Addition Fifty-One Baxter Road, LLC 51B Baxter Road 49-16 House: 1886/ 1887 Garage and Shed: ND 2nd Dwelling w/Garage: 2009 1991 – Repair windows, shingle, decking, pantry flr 1991 – Add 8’6” x 14’ to existing 2nd flr BR 1 BU no heat 1994 – Add 126 sf 1st flr kitchen and 72 sf 2nd fl bath & improve baths on 2nd flr 1994 – demo shed 1995 – demo garage 2009 – Relocate building on new finished full basement 1905 sf – add 255 sf & reno 1st flr 2025 sf, 2nd flr reno 1349 sf – windows and doors & amendment to reframe porch and replace sunroom walls & ceiling, new windows 2009 – Build 2 story, one bed 1DU 807 sf 1st inc. garage 283 sf 2nd 2011 – Remove existing beach stairs & replace w/new 51A Baxter Road 49-16.1 F:\WpS\SBPF, Inc\Table of Homes 1978 or earlier.docx Attachment E Annual Review – Sconset Geotextile Tube Project (SE48-2824) (dated December 13, 2016) Submitted to: Nantucket Conservation Commission 2 Bathing Beach Road Nantucket, Massachusetts 02554 Submitted by: Siasconset Beach Preservation Fund P.O. Box 2279 Nantucket, Massachusetts 02584 Prepared by: Epsilon Associates, Inc. 3 Mill & Main Place, Suite 250 Maynard, Massachusetts 01754 December 13, 2016 Annual Review –Sconset Geotextile Tube Project (SE48-2824) Nantucket, MA 21597/Sconset i Annual Review Epsilon Associates, Inc. TABLE OF CONTENTS EXECUTIVE SUMMARY 1 1.0 Introduction 1 2.0 Monitoring Results 1 2.1 Sand Delivery 1 2.2 Bluff Monitoring 2 2.2.1 Beach Contribution Volume 3 2.3 Shoreline Monitoring 3 2.4 Wetland Well Monitoring 5 2.5 Beach Invertebrate Monitoring 6 2.6 Underwater Video Monitoring 6 2.7 Annual Drainage System Report 7 3.0 Recommended Changes to Monitoring and Mitigation Program 7 3.1 Monitoring Program Adjustments 8 3.2 Mitigation Volume Adjustment 10 FIGURE 1 Elevation Contours Generated from Results of 2016 UAV Aerial Survey FIGURE 2 Volume Displacement of Sand for Bluff Areas on Sconset Beach ATTACHMENT A APRIL 2015 – MARCH 2016 SAND DELIVERY AND CONTRIBUTION REPORT ATTACHMENT B SUPPLEMENTAL HISTORICAL ANALYSIS OF SURVEY DATA AT SIASCONSET, NANTUCKET, MA ATTACHMENT C 2016 WETLAND WELLS GROUNDWATER LEVEL MONITORING ATTACHMENT D INTERTIDAL BENTHIC INVERTEBRATE SAMPLING, SCONSET BLUFF GEOTEXTILE PROJECT, MA ATTACHMENT E SCONSET BEACH UNDERWATER VIDEO SURVEY REPORT ATTACHMENT F DRAINAGE SYSTEM MONITORING 21597/Sconset E-1 Annual Review Epsilon Associates, Inc. EXECUTIVE SUMMARY 1.0 Introduction The Sconset Beach Preservation Fund (SBPF) is permitted under SE48-2824 to install geotextile tubes at the base of the bluff below 87-105 Baxter Road, vegetate the bluff, and install a coastal drainage system (including a catch basin) at 91 Baxter Road. As part of the Order of Conditions for the geotextile tube project, an annual review of the Project is required to review the Project’s monitoring and mitigation programs. This Annual Report has been prepared to review the existing monitoring data (Section 2.0) and provide recommended changes to monitoring and mitigation programs for the future (Section 3.0). 2.0 Monitoring Results Individual monitoring reports have been submitted for the following activities and are presented in Attachments A-F: ♦ Sand delivery report (Attachment A) ♦ Bluff monitoring report (included in Attachment A) ♦ Shoreline monitoring (Attachment B) ♦ Groundwater monitoring in wetlands wells (Attachment C) ♦ Beach invertebrate monitoring report (Attachment D) ♦ Underwater video monitoring report (Attachment E) ♦ Drainage system annual report (Attachment F) The following sections provide a summary of each of the referenced monitoring reports. 2.1 Sand Delivery As presented in the “April 2015 - March 2016 Sand Delivery and Contribution Report” included as Attachment A and discussed in detail with the Commission on August 24, 2016, the Project incorporates a substantial mitigation volume of 22 cubic yards(cy)/linear foot (lf) /year (yr). Given the project’s length of 947 feet, the total annual mitigation volume required is 20,834 cy. As required by the Project’s Order of Conditions (SE48-2824), the 22 cy/lf/yr must be placed by March 31 of any given year. Delivery tickets must be provided annually to document the total volume of sand provided on a yearly basis. 21597/Sconset E-2 Annual Review Epsilon Associates, Inc. As detailed in Tables 1-4 of Attachment A, the information in Tables 1-4 demonstrates that the sand mitigation requirements for the three “Sand Years” for the Project (December 2013 – March 2014; April 2014 – March 2015; and April 2015 – March 2016) have been met, with a small surplus 2.2 Bluff Monitoring As presented in the “April 2015 - March 2016 Sand Delivery and Contribution Report” included as Attachment A and discussed with the Commission on August 24, 2016, SBPF intends to perform an annual survey of the bluff face at the beginning of each Sand Year (Around April 1 of any given year). The first such annual aerial bluff survey since the Project’s Order of Conditions was issued was performed of the Project area on April 2, 2016. A UAV was used to capture imagery and elevation data for the bluff face and geotextile area. The images were stitched together using photogrammetric techniques to create a photomosaic. These were geo-referenced using control points for location accuracy. The elevation data from the survey was then processed and used to produce a digital elevation model and 1-foot contours of Sconset Bluff (Figure 1). A 3D model of the bluff face above the geotextile tubes as well as north and south of the bluff was also generated from this data. The survey yielded the following findings: ♦ The results of the 2016 aerial survey were compared to the most recent previous aerial survey from July 2013 (just before geotextile tube installation in December 2013 and January 2014) for those unprotected areas immediately adjacent to the north and south of the geotextile tube project. Over the last three years, the average, distance-weighted unprotected bluff contribution volume was 12.9 cy/lf/yr, which is 59% of the 22 cy/lf/yr mitigation volume. See attached Figure 2.1 ♦ As of April 2016, the volume of sand in the sand template is 14,022 cy, which is about 14.8 cy/lf. This template volume includes the volume of sand in the sand ramps. ♦ The Sand Delivery Report demonstrates that all 22 cy/lf/yr of the mitigation volume have been delivered. The April 2016 survey shows that, of the total delivered volume, about 18.1 cy/lf/yr have been contributed to the littoral system.2 1 The unprotected bluff areas were selected so as to exclude the areas of the sand ramps. 2 The volume contributed is shown in Table 7 of Attachment A and includes contribution from the template (including sand ramps), erosion of bluff face above the geotextile tubes, and contribution of mitigation sand during construction. 21597/Sconset E-3 Annual Review Epsilon Associates, Inc. ♦ The Project has contributed more sand (18.1 cy/lf/yr) than the unprotected bluff (12.9 cy/lf/yr) over the last three years. 2.2.1 Beach Contribution Volume During the Commission’s August 24, 2016 meeting when an interim update on the monitoring data was presented, a request was made to review and compare the change in beach volume over the last three years within and directly adjacent to the geotextile tube areas, similar to the calculation of bluff volume erosion. There are some important differences between beach erosion and bluff erosion: while a bluff may only remain stable or erode, beaches may gain or lose volume (seasonally or otherwise), leading to significant changes within any given time period. A review of volume change data for the profiles within the geotextile tube area (profiles 91 and 91.5) and the immediately adjacent unprotected areas to the north (profiles 92 and 92.5) and south (profile 91 is also the closest profile to the short unprotected southern segment) shows that, in the period before the geotextile tubes were installed, volume change amongst this group of profiles varied significantly on a quarterly, semi-annual, or annual basis. As an example, in the semi- annual period right before the geotextile tubes were installed (March 2013 to September 2013), the profiles in the geotube area (profiles 91 and 91.5) gained 9.9 and 3.5 cy/ft, respectively, while the profiles just north of the geotextile tubes (92 and 92.5) lost 0.2 or gained 8.0 cy/ft. A review of additional pre-geotextile tube volume change data likewise demonstrates that there is tremendous variability in the reported volume change between the profiles. This natural variability suggests that an attempt to compare beach volume change between profiles within the geotextile tube areas and immediately adjacent unprotected areas is of limited value. A more useful comparison is to review each profile individually and determine how data collected after the geotextile tubes were installed compares to data collected prior to geotextile installation. Such a comparison is presented below in Section 2.3. 2.3 Shoreline Monitoring Shoreline monitoring occurs quarterly at 46 profiles located along six miles of shoreline. Each shoreline survey includes information on the change in the position of the shoreline (the Mean Low Water [MLW] line) and the change in volume for each profile. Bathymetry is conducted each spring and fall out to -25 or -35 feet MLW92 or 2,000 to 3,000 feet offshore, whichever is farthest. Adverse impacts from the geotextile tubes would be expected to be most apparent in the areas immediately adjacent to the geotextile tubes. One of the purposes of the shoreline monitoring is to ensure that the long-standing pattern of shoreline retreat in the Project area and immediately adjacent areas is not accelerating due to the presence of the geotextile tubes. To provide a comprehensive assessment, shoreline monitoring also occurs at profiles farther to the north and south of the geotextile tubes that were established in the 1990’s, for a total monitoring distance of approximately six miles. 21597/Sconset E-4 Annual Review Epsilon Associates, Inc. A detailed analysis of shoreline survey data entitled “Supplemental Historical Analysis of Survey Data At Siasconset, Nantucket, MA” was prepared by Woods Hole Group and is included as Attachment B. This analysis reviews the shoreline monitoring data and also provides recommendations on the most useful types of ongoing data collection and analysis. Shoreline monitoring data from 8 beach profiles that represent the stretch of beach subject to monitoring were reviewed in Section 2.1 of Attachment B, including: ♦ Near the south of the monitoring area (Profile 84) ♦ Approximately 1,000 ft and 500 ft south of the geotubes (Profiles 90 and 90.6) ♦ Within the geotube area (Profiles 91 and 91.5) ♦ Approximately 500 ft and 1000 ft north of the geotubes (Profiles 92.5 and 93) ♦ Near the north end of the monitoring area (Profile S) General observations derived from the plotted shoreline data included in Attachment B are: ♦ There is an overall pattern of shoreline retreat within the Project area. The shoreline retreat is not constant, as each profile includes times of shoreline advance and shoreline retreat, demonstrating a high degree of variability on short and long time scales. This long-standing overall pattern of shoreline retreat is expected to continue after the geotextile tubes installation, since the geotextile tubes are designed to protect the base of the bluff from further erosion, not to prevent shoreline erosion. ♦ The high degree of natural variability in the position of the shoreline, with observed short term periods of erosion or accretion, suggests that adverse effects from the geotextile tubes could only be reliably determined through the prevalence of sustained periods (2 years or more) of shoreline erosion in excess of the historic observations. ♦ Each profile responds differently on variable time scales. ♦ This variability means that attempts to fit a long-term trend line do not have a high degree of statistical accuracy. ♦ Within the selected subset of eight profiles, the current (August 2016) shoreline position is generally similar (within about 20 feet) to the shoreline position in the ~2005-2008 timeframe, although there is substantial variability (up to 50 feet of cumulative difference) between these dates. In other words, the current shoreline is in a position that was previously recorded under natural conditions, prior to the 21597/Sconset E-5 Annual Review Epsilon Associates, Inc. installation of the geotextile tubes, which indicates that the presence of the geotextile tubes is not having an adverse impact on the shoreline position. ♦ The short-term variability shown by surveys since geotube installation in January 2014 is similar to short-term variability (~2-3 year periods) observed over many years of surveys before the geotubes were installed. Surveyed post-geotube shoreline changes are not materially different from previous observations as related to rates and duration of shoreline change. No accelerated erosion post-geotube installation in excess of historical observations is evident. Additionally, as presented in Section 2.2 of Attachment B, there is a strong linear relationship between shoreline position and volume change. This shows that shoreline position may provide a reliable indicator of beach volume change. Finally, as requested by the Conservation Commission, a mapset of the beach topography in the geotextile tube area and immediately surrounding areas has been prepared using the October 2016 survey data. This mapset is included as Figures A-1 through A-3 at the end of Attachment B. Figures A-1 through A-3 show contours from elevation 0 to 15 MLW92 (the toe of the bluff is typically around elevation 10 MLW92). The beach contours from elevation 0 to 10 MLW92 within the geotube areas and immediately adjacent areas are broadly congruent, with similar spacing and locations. The contours from elevation 10 to 15 MLW92 are more tightly-spaced in front of the geotextile tubes, reflecting the steep face of the mitigation template, and more loosely-spaced in the unprotected areas just to the north and south, reflecting the typical slope of the unprotected upper beach and lower bluff and the ongoing bluff erosion in these unprotected areas. South of profile 90.8, the contours from elevation 10 to 15 MLW92 are more closely-spaced, reflecting the widespread use of jute or coir terraces at the base of the bluff. Overall, the beach topography maps show similar beach elevations in the geotextile tube area and immediately adjacent areas and are not indicative of an adverse effect from the geotextile tubes. 2.4 Wetland Well Monitoring As presented in “2016 Wetlands Wells Groundwater Level Monitoring” included as Attachment C, monitoring wells were installed in June 2016 at three locations along the western side of Baxter adjacent to the bordering vegetated wetlands (see Figure 1 in Attachment C). Water levels in the wells were monitored on June 28, 2016, July 28, 2016, and September 12, 2016. Wells were monitored in response to a concern that the installation of the drainage system, including the catch basin at 91 Baxter Road, may impact (lower) water levels within the wetlands. Such an impact was not expected since the catch basin was installed across the road from the wetland and would receive only runoff from the eastern side of Baxter Road under normal conditions. During the three months of wetland monitoring in 2016, water levels in each individual well varied by about 1-2 feet. Such variation is within the range of expected variation (based on 50 previous well readings 21597/Sconset E-6 Annual Review Epsilon Associates, Inc. observed during a 6-year period from 2001-2007) and correlates with precipitation data. Accordingly, there is no evidence of harm to water levels in the wetland from the installation of the catch basin. No further monitoring is recommended. 2.5 Beach Invertebrate Monitoring As presented in “Intertidal Benthic Invertebrate Sampling, Sconset Bluff Geotextile Project, MA” included as Attachment D, CR Environmental, Inc. (CR) of East Falmouth, MA collected twelve benthic grab samples from four areas within the intertidal zone of Siasconset Beach and surrounding areas on August 16-18, 2016. The four sampling zones included the Project Area (91, 91.2, 91.5) in the vicinity of the geotubes, south of Codfish Park (82, 83, 84), between the Project Area and Hoick’s Hollow (93, 94, 95) and north of Hoick’s Hollow (96, 96.5, 97), as required by the Order of Conditions (see Figure X in Attachment D). The high energy environment of Siasconset Beach is reflected in the faunal results. Only eight species were found in this harsh environment, and with the exclusion of the mole crab Emerita and the beach flea Talorchestia, only single specimens of the six other species were found (Table 2). All of the species are types of crustaceans commonly found in sandy intertidal environments (i.e. amphipods, skeleton shrimp, hooded shrimp, mole crabs, isopods). Organisms in samples within the Project Area were not markedly different from those found to the north or south. Species number (richness) within the Project Area ranged from 1 to 3. At other sampling sites species richness ranged from 0 at Station 97 to the north of Hoick’s Hollow to 4 at Station 93 between the Project Area and Hoick’s Hollow. Mole crabs were the dominant species at all locations. The low density and diversity of marine fauna in the various samples from Siasconset Beach is not surprising given the coarse sediments. Tidal and wave action continuously moves the intertidal sediments providing a very hostile environment for marine fauna. The continual movement and reworking of sediments hinders the establishment of most species. There was no evidence of harm to intertidal invertebrates in the Project Area, proximate to the geotubes, compared to the other sampling stations. In addition, no representatives of a resource species were found at any of the twelve sampling stations. Additional monitoring is not warranted given the low species diversity, low abundance and lack of noteworthy species found within the sandy intertidal beach habitat of Siasconset Beach. 2.6 Underwater Video Monitoring As presented in “Sconset Beach Underwater Video Survey Report” included as Attachment E, on June 15, 2016, CR Environmental, Inc. (“CR”) and Epsilon conducted underwater video surveys offshore from the geotube project site and directly adjacent areas at the base of the bluff from 87-105 Baxter Road. Underwater video data was collected with CR’s portable towed video sled along the transects shown on Figure 1 in Attachment E. 21597/Sconset E-7 Annual Review Epsilon Associates, Inc. The survey showed that a productive habitat area is located just offshore from the geotextile tubes, with no indication of loss of cobble habitat. During the underwater video survey, twelve invertebrate species, four fish species, and five marine plant and algal species were observed. The dominant biota across all transects included unidentified branching brown algae, unidentified branching red algae, bread crumb sponge, black sea bass, and common skate. Most of the survey area had 25-55% cobble coverage, and there is no indication that such habitat is being covered by the sand mitigation. A comparison of the 2016 survey with a 2007 survey demonstrates that results were broadly consistent and did not indicate loss of cobble habitat due to the geotextile tubes. The required fall survey was conducted in October 2016 and the report will be submitted within 60 days of the survey. A comparison of the survey results with historic bathymetry in the area indicates that bottom elevations in the area a few thousand feet offshore of the geotextile tubes can vary annually by several feet due to regional sand or shoal movements. These natural sand and shoal movements are far more significant than the small volume of the mitigation sand template. The small volume of the sand template is illustrated by the following calculation, which considers an extremely unlikely scenario: if the entire sand template volume of 20,834 cubic yards washed directly offshore in a small area (to be conservative, this area was assumed to be 1,000 feet alongshore [the length of the geotextile tubes] by 1,600 feet offshore [the approximate distance to the depth of closure]), with no sand transport to the north or south and no transport farther offshore, the depth of coverage would be about four inches. Even considering this extremely unlikely scenario, the potential impact to offshore bathymetry from the sand template is minimal compared to natural bathymetric variability and therefore would neither be harmful nor clearly discernible. Underwater video monitoring could only generate meaningful information in the event that regular monitoring indicates that the sand mitigation template is contributing several times more sand than the unprotected bluff. Therefore, it is recommended that underwater video monitoring only occur once every three years or in the event that the mitigation template contributes 3-5 times more sand than the unprotected bluff. 2.7 Annual Drainage System Report The function of the stormwater drainage system has been monitored in accordance with the Stormwater Operation and Maintenance Plan. As noted in Attachment F, “The system appears to be functioning as designed, and we do not have any immediate concerns. There is approximately four-inches of accumulated sediment in the base of the catch basin, which is below the threshold for cleaning. We will continue to monitor the system.” 3.0 Recommended Changes to Monitoring and Mitigation Program The Project’s mitigation and monitoring programs were reviewed to determine those types of monitoring that provide the most useful data and value in assessing the potential impacts from the geotextile tubes, and which do not. 21597/Sconset E-8 Annual Review Epsilon Associates, Inc. 3.1 Monitoring Program Adjustments ♦ Aerial bluff monitoring should occur annually to provide an assessment of bluff volume change in protected and unprotected areas, as well as the volume of sand remaining in the sand template. ♦ Shoreline surveys should be adjusted to collect the most meaningful data. Nine surveys have been completed in the nearly three years since the geotextile tubes were installed in December 2013/January 2014 (survey dates: April 2014, October 204, April 2015, July 2015, October 2015, March 2016, May 2016, August 2016 and October 2016). As presented in Attachment B, the following adjustments are recommended for the ongoing shoreline surveys and reports: o Plots of shoreline trends should be included in ongoing shoreline monitoring reports. o Shoreline monitoring frequency should be changed to a maximum of two times a year. As presented in Attachment B, a seasonal analysis of the shoreline position was conducted to determine if particular times of year are more indicative of overall shoreline change. This analysis did not reveal meaningful season variability; trends and variability are similar regardless of season. Annual and longer term trends would be resolved with surveys a maximum of twice per year. Quarterly sampling and observation does not inform the analysis to any greater degree. Therefore, a survey frequency of a maximum of two times a year is recommended. This also is consistent with the monitoring suggestions in the MassDEP Beach Nourishment Best Practices Guide (MassDEP, 2007), which suggest seasonal surveys for a year or so, followed by annual surveys for monitoring beach nourishment projects. The National Research Council also recommends a similar approach to beach profile monitoring, which suggests reducing the frequency of surveys over time (National Academy Press, 1995). To be consistent with standard engineering practice, which typically is focused on capturing an eroded “winter” profile along with a recovered “summer” profile after more quiescent periods, if there will be two surveys per year, one survey is recommended in late winter / early spring and the other is recommended in late summer. These surveys also would be consistent with and comparable to long-term data. o Wading shots should be eliminated from the shoreline surveys. As presented in Attachment B, wading shots are conducted to collect data from 0 to -5 feet MLW and require a rod man adequately equipped to swim in the water, and a survey rod capable of withstanding the conditions. Each individual survey point can take several attempts as the rodman finds safe footing in the surf, and as a surveyor with a transit on the beach gains a visual fix on the survey rod. An analysis of extrapolating the data from 0 to -5 feet MLLW, as opposed to using a 21597/Sconset E-9 Annual Review Epsilon Associates, Inc. rodman to collect the data, shows that associated errors are small (the average difference in the volume of sand estimated for each profile was 1.1 cy/ft, which equates to a 1.4% difference) The surveys can be completed in approximately half the time if there are no wading shots, which would add tremendous flexibility to completing the surveys in timely fashion, and also reduces inherent risks to the survey crew. o Bathymetry monitoring frequency should be changed to once per year. The bathymetry offshore Siasconset features a generally stable profile, particularly in the northern and central portions of the monitoring area (which includes the geotextile tubes). Bathymetry data are helpful for general scientific purposes to understand regional coastal processes (e.g., offshore shoal movements and evolutions), but are not conclusive for determining whether the geotextile tubes are having an adverse impact upon adjacent beaches. Shoreline position data are most useful for that purpose. Bathymetry surveys conducted a maximum of once per year are sufficient to characterize regional morphology. In addition, fewer transects could be surveyed (particularly in the northern portion of the monitoring area) without sacrificing information to understand the regional processes. Reducing the total number of bathymetry survey profiles to ~22 that extend no more than 3,000 ft offshore would potentially allow for the survey to be completed in a single calm sea/weather day without sacrificing substantive information. To provide useful data for present and long-term comparisons, the subset of ~22 profiles would include the historic whole number profiles 81 through 99 plus profiles Q, S, and W. Additionally, it is proposed that bathymetry monitoring be re-evaluated annually to assess its continued value. ♦ Groundwater levels in wetlands wells should be discontinued. The existing monitoring data show that there are no discernible effects from the catch basin, results correlate with precipitation, and no ongoing impacts are anticipated. ♦ Beach invertebrate monitoring should be discontinued. The existing monitoring data show that there are no impacts from the geotextile tubes and that additional monitoring is not warranted given the low species diversity, low abundance and lack of noteworthy species found within the sandy intertidal beach habitat of Siasconset Beach. ♦ Underwater video monitoring should only be required once every three years or in the event that regular monitoring indicates that the sand mitigation template is contributing several (3-5) times more sand than the unprotected bluff. ♦ Drainage system reporting: The drainage system monitoring is proposed to be continued for one more year. After that time, the Town Director of Public Works will monitor the catch basin for maintenance, as is done for other Town catch basins. 21597/Sconset E-10 Annual Review Epsilon Associates, Inc. 3.2 Mitigation Volume Adjustment The current mitigation requirement is to place a minimum of 22 cy/lf/yr annually. As has been noted in previous submissions (see November 1, 2013 memorandum from Epsilon Associates), the average annual bluff contribution volume, calculated from 1994-2013, is 14.3 cy/lf/yr. The conservative volume of 22 cy/lf/yr is 1.5 times the average bluff contribution. A review of ten comparable bluff and dune protection projects presented in Attachment B indicates that associated mitigation volumes are based upon average annual erosion of the bluff or shoreline multiplied by the height and length of the shoreline protected. This review demonstrates that the significant mitigation required at Sconset (equivalent to 1.5 times the bluff contribution volume) is uniquely conservative. The conservative nature of the mitigation volume sand is evidenced by the fact that approximately 14,000 cy of sand remained in the mitigation template in April 2016, at the end of the 2015-2016 winter. SBPF proposes a more adaptive mitigation program, where the mitigation volume is set at 14.3 cy/lf/yr, with an ongoing requirement to keep the geotextile tubes covered on an as-needed basis throughout the year. In this manner, the required mitigation volume is adaptive and would be higher than the 14.3 cy/lf/yr during a more energetic winter if the geotextile tubes became exposed and required more sand to keep them covered. Under this proposed scenario, a minimum mitigation volume of 14.3 cy/lf/yr would be provided in the mitigation template by March 31 of each year, with the requirement that at least 10-14 cy/lf of mitigation sand are available on the template at the beginning of the winter storm season (consistent with current requirements in the current Order of Conditions). Throughout the winter as needed to keep the geotextile tubes covered, mitigation sand would be pushed down from the top of the template to the face of the template. If winter conditions are such that frequent recovering is required and the entire 14.3 cy/lf/yr is contributed, then additional mitigation sand would be required in an amount sufficient to keep the geotextile tubes covered through the winter. In this manner, the volume of mitigation sand is set at a minimum of 14.3 cy/lf/yr and will be adapted to a higher volume based upon encountered conditions. We believe this adaptive monitoring approach will allow the mitigation sand requirement to more closely mimic natural conditions. Attachment A April 2015 – March 2016 Sand Delivery and Contribution Report April 2015 - March 2016 Sand Delivery and Contribution Report Baxter Road and Sconset Bluff Stabilization Project Nantucket, MA June 6, 2016 Submitted by: Siasconset Beach Preservation Fund PO Box 2279 Nantucket, MA 02584 Prepared by: Epsilon Associates 3 Clock Tower Place, Suite 250 Maynard, MA 01754 In Association with: Cottage + Castle, Inc. 37 Old South Road, Unit #6 Nantucket, MA 02554 21597/Sconset 1 2016 Annual Sand Delivery Report Epsilon Associates, Inc. ANNUAL SAND DELIVERY REPORT 1.0 Introduction The Baxter Road and Sconset Bluff Stabilization Project (the “Project”) was constructed in two phases. The first phase was constructed in late December 2013 and January 2014 under an Emergency Certification approval issued by the Nantucket Conservation Commission. The first phase consisted of the installation of three stacked tiers of 45-foot circumference geotextile tubes at the base of the eroding Sconset Bluff. The geotextile tube installation was approximately 852 feet long and extends along the toe of the bank from 87- 105 Baxter Road. The second phase was constructed in October 2015 through February 2016 and includes the installation of a fourth tier of geotextile tubes on lots 91-99, intermediate returns, end returns, and a surface runoff drainage system. With the returns included, the total project length is now 947 feet. The purpose of the annual sand delivery report is to present the sand mitigation volumes and corresponding delivery tickets for each “Sand Year” from April 1 through March 31 of any given year. SBPF has previously submitted detailed Sand Reports for the first two sand years associated with the Project: November 2013 – March 31, 2014 (referred to as the “2014 Sand Year”) and April 1, 2014 through March 31, 2015 (referred to as the “2015 Sand Year”). This report presents final information on sand deliveries during the period from April 1, 2015 through March 31, 2016 (referred to as the “2016 Sand Year”). A preliminary report was submitted on March 4, 2016. 2.0 Sand Delivery Requirements The Project incorporates a substantial mitigation volume of 22 cubic yards(cy)/linear foot(lf)/year(yr). Given the project’s length of 947 feet, the total annual mitigation volume required is 20,834 cy. As required by the Project’s Order of Conditions (SE48-2824), the 22 cy/lf/yr must be placed by March 31 of any given year. Delivery tickets must be provided annually to document the total volume of sand provided on a yearly basis. 3.0 Volume of Mitigation Sand Delivered The following four tables document the sand delivery amounts. ♦ Table 1 presents a summary of the volume of sand provided from December 2013 through the end of March 2016. ♦ Table 2 presents the volume of sand delivered during the period from December 2013 – March 31, 2014, which includes construction of the initial Project. ♦ Table 3 presents the total volume of mitigation sand delivered during the period from April 1, 2014 – March 31, 2015. 21597/Sconset 2 2016 Annual Sand Delivery Report Epsilon Associates, Inc. ♦ Table 4 presents the total volume of sand delivered during the period from April 1, 2015 – March 31, 2016. The information in Tables 1-4 demonstrates that the sand mitigation requirements for the period of April 1, 2015 – March 31, 2016 have been met, with a small surplus. Each of these tables is discussed in further detail below. 3.1 Table 1. Summary Volume Lines 1-6 of Table 1 provide a summary of the required mitigation volume. The base mitigation volume is determined by multiplying 22 cy/lf/yr by the Project’s length (Line 1). This volume is then adjusted by subtracting out the surplus sand from the previous year and the amount of sand eroded from the bluff face. The surplus sand is calculated as that sand delivered the previous year that is in excess of the base mitigation requirements and that is still in the sand template at the end of the sand year (see Lines 2-4). The bluff erosion volume accounts for that portion of the bluff face that continued to erode and is discussed further in Section 5.0 below. Line 7 presents the total volume delivered for mitigation sand. Lines 9-11 of Table 1 describe the total volume of sand delivered to the site, and separate this total into the following categories: mitigation sand, sand used on the bluff face, and sand used for construction (inside or behind the geotextile tubes). Neither sand placed on the bluff face nor sand used for construction is counted towards the mitigation requirement. Line 8 of Table 1 presents the final calculation of whether the project’s mitigation requirement was met. Any surplus of sand delivered during one sand year, up to but not in excess of the amount remaining on the sand template on the beginning of the new sand year on April 1, is carried forward and counted towards the following year’s requirement. 3.2 Table 2. Sand Delivery December 2013 – March 31, 2014 Table 2 presents the volume of sand delivered during the period from December 2013 – March 31, 2014, which includes construction of the initial Project. Table 2 provides a detailed breakdown of that portion of sand placed within and behind the geotextile tubes and presents the total volume of mitigation sand placed over, in front of, and at the ends of the geotextile tubes. All delivery tickets for the total volume delivered of 39,204 cy were previously submitted to the Conservation Commission, most recently as part of the 2015 Sand Report. 3.3 Table 3. Sand Delivery April 1, 2014 – March 31, 2015 Table 3 presents the total volume of mitigation sand delivered during the period from April 1, 2014 – March 31, 2015. Three separate deliveries were made over this period of time. All delivery tickets for the total volume delivered of 14,428 cy were submitted as part of the 2015 Sand Report. 21597/Sconset 3 2016 Annual Sand Delivery Report Epsilon Associates, Inc. 3.4 Table 4. Sand Delivery April 1, 2015 – March 31, 2016 Table 4 presents the total volume of sand delivered during the period from April 1, 2015 – March 31, 2016. Table 4 provides a detailed breakdown of the sand delivered for construction, sand delivered for mitigation, and sand delivered to the bluff face. All delivery tickets for the total volume of 22,485 cy delivered during the 2016 Sand Year are attached, including the 19,066.77 cy delivered during the most recent construction period in November, December, and January and the 3,418 cy delivered in April 2015. 3.5 Summary The information in Tables 1-4 demonstrates that the sand mitigation requirements for the period of April 1, 2015 – March 31, 2016 have been met, with a small surplus. 4.0 Annual Aerial Survey of Bluff SBPF intends to perform an annual survey of the bluff face at the beginning of each Sand Year, to facilitate the calculation of the annual change in volume of (1) the bluff face above the geotubes and (2) the unprotected bluff sections to the north and south of the geotextile tubes. April 2016 is the first Sand Year since the Project’s Order of Conditions was issued and as such represents the first year of the planned annual bluff survey. An aerial survey was performed of the Project area on April 2, 2016. A UAV was used to capture imagery and elevation data for the bluff face and geotextile area. The images were stitched together using photogrammetric techniques to create a photomosaic. These were geo-referenced using control points for location accuracy. The elevation data from the survey was then processed and used to produce a digital elevation model and 1-foot contours of Sconset Bluff. A 3D model of the bluff face above the geotextile tubes as well as north and south of the bluff was also generated from this data. 5.0 Changes in Bluff Volume To understand changes in the bluff volume since project construction, the results of the 2016 survey were compared to the previous aerial photogrammetry survey of the Project area that was conducted in July 2013. The July 2013 survey was conducted about 6 months prior to the installation of the geotextile tubes. 5.1 Changes in Bluff Volume Above Geotextile Tubes The change in the bluff volume from 2013 to 2016 was calculated by first generating a 3D digital elevation model from the 2016 survey data of that portion of the bluff above the elevation of the geotextile tube sand cover, which was at approximately +34 feet Mean Low Water (MLW) at the time of the April 2016 survey. Similarly, the 2013 photogrammetry survey data was used to construct a 3D model to compare against the 2016 survey. The 2013 data was subtracted from the new survey data and the volumetric change was calculated in GIS based on the results. 21597/Sconset 4 2016 Annual Sand Delivery Report Epsilon Associates, Inc. In the 2015 Sand Report, it had been anticipated that some of the bluff above the geotextile tubes had continued to erode due to runoff and surface water breakout after the geotubes were installed and prior to bluff vegetation and stormwater control efforts undertaken in 2015. The bluff was initially vegetated in spring 2015 and the proposed stormwater management system was installed in January/February 2015; therefore, it had been anticipated that some erosion of the top and face of the bluff had continued prior to the implementation of these efforts. . Additionally, during construction of the fourth tier and returns in fall 2015, some of the sand that had been placed on the bluff face prior to vegetation slumped down. This sand, which had not previously been counted as mitigation, then became available to the littoral system. Since the purpose of the mitigation volume is to replicate that amount of sand that would have eroded from the bluff on an annual basis without the Project, it is appropriate to account for that volume of the bluff that eroded and to subtract this volume from the mitigation requirement. As shown in Table 5, direct comparison of the bluff survey data from April 2016 to July 2013 indicates that the bluff face decreased in volume by 851 cy. However, a total volume of 7,069 cy of sand was added to the bluff face during initial construction in early 2014, prior to vegetation in spring 2015 to smooth the bluff face, and during construction in fall 2015 to fill gullies (see Table 5). When the addition of 7,069 cy of sand is taken into account, the bluff face above the geotube sand cover would have decreased in volume by approximately 7,920 cy (851 cy +7,069 cy) but for the addition of 7,069 cy added to fill gullies and smooth the bluff surface for vegetation. In order to fill out the columns in Table 1, this total (7,920 cy) was apportioned as 6,000 cy in 2014-2015 and 1,920 cy in 2015- 2016. The change in bluff face volume will continue to be measured annually. Now that the bluff face has been vegetated and the stormwater system has been installed, any future changes in bluff face volume are expected to be minimal. 5.2 Changes in Bluff Volume in Adjacent Unprotected Areas The results of the 2016 aerial survey were also used to calculate the changes in the bluff volume from 2013 to 2016 for those unprotected areas immediately adjacent to the geotextile tube project. The change in the bluff volume in these unprotected areas was calculated from the toe of the bluff (elevation +11 MLW) to the top of the bluff. Similar techniques were used as in 5.1, and the results were used to show the net loss between study periods. For the north unprotected area, the section of bluff within 800 feet immediately to the north of the geotextile tubes was used. For the south unprotected area, the section on bluff within 210 feet immediately to the south of the geotextile tubes was used. Areas farther south than this could not be used because they had coir or jute terraces installed and so were not representative of the unprotected bluff. 21597/Sconset 5 2016 Annual Sand Delivery Report Epsilon Associates, Inc. As shown in Table 6, this analysis indicates that the unprotected areas immediately adjacent to the geotextile tubes eroded a total of 35,699 cy from July 2013 – April 2016. This is equivalent to an average of 12.9 cy/lf/yr. 6.0 Volume of Sand in Template The volume of the sand template was calculated by determining the total volume of sand within the sand cover at the time of the 2016 aerial survey, and subtracting out the known volume of sand within the geotextile tubes and returns located above beach level. The total volume of sand within the sand cover at the beginning of April 2016 was 14,022 cy. Calculations were also performed of that portion of the sand template that is located above the fourth tier. Per the Project’s Order of Conditions, the sand on top of the fourth tier is not counted towards the mitigation sand. This volume is calculated as 2,200-2,300 cubic yards. It is anticipated that sand on top of the sand template, including sand on top of the fourth year, will continue to be pushed down to recover the geotextile tubes as needed. Additionally, the 2,200-2,300 cy that are presently unavailable, but will become available in the future as the sand is pushed down, is less than the Project surplus of just over 3,000 cy. 7.0 Volume of Sand Contributed to Littoral System Table 7 presents the approximate volume of sand contributed to the littoral system. As shown in Table 1, the Project has delivered all the mitigation sand to the site that is required under the Order of Conditions. As has been previously noted, the mitigation sand is delivered to the top of the geotextile tubes and then pushed over to cover the face of the tubes. On an as-needed basis throughout the winter, the sand on top of the geotextile tubes is pushed from the top of the tubes to the face of the tubes whenever needed to recover the face of the geotextile tubes. Table 7 has been prepared to provide a reasonable estimate of how much mitigation sand has entered the littoral system over the past three years. For each of the three sand years (Sand Year 2014, Sand Year 2015, and Sand Year 2016), this estimate was calculated by the following steps shown in Table 7: 1. Beginning with the volume of sand in the sand template at the start of each year (this was estimated in Sand Years 2014 and 2015 and measured in Sand Year 2016); 2. Adding the total amount of mitigation sand delivered each year (this is a known amount for each Sand Year), 3. Subtracting the volume of sand in the sand template at the end of each year (this was estimated in Sand Years 2014 and 2015 and measured in Sand Year 2016); 4. Adding the bluff volume eroded (this is known as a total from 2013 through 2016 and was apportioned to Sand Years 2015 and 2016 as described above in Section 21597/Sconset 6 2016 Annual Sand Delivery Report Epsilon Associates, Inc. 5.1; that portion of the bluff that slumped down during construction in Sand Year 2016 is counted in the following bullet), 5. Adding the volume of sand contributed during construction (this is known from 2013 and was apportioned to Sand Year 2016 as described above in Section 5.1); 6. Determining the total volume of sand contributed (both as a total volume and as a rate expressed in cy/lf/yr), including as an average rate from 2013-2016. These calculations show that the Project has contributed an average of 18.1 cy/lf/yr (although all 22 cy/lf/yr have been delivered to the site and are available for contribution). This volume is higher than the average contribution of 12.9 cy/lf/yr of the unprotected bluff to the north and south of the Project. Tables Page 1 of 4 Sconset Bluff and Baxter Road Geotextile Tube Project, 87-105 Baxter Road, Nantucket, MA Table 1. Summary of Sand Delivery in Cubic Yards (CY), December 2013 - March 31, 2016 Line Sand Amounts 12/13-3/31/14 4/1/14-3/31/15 4/1/15-3/31/16 4/1/16-3/31/17 1 Required Mitigation Volume (22 cy/lf * Project Length of 852' for 3 tiers, 947' for 4 tiers w/ret.)18,744 18,744 20,834 20,834 Surplus Sand From Prior Year 2 Surplus Delivered in Prior Year (From Line 9 in Preceding Column)0 5,207 6,892 3,062 3 Volume on Template at Start of Sand Year 0 5,900 8,500 14,022 4 Countable Surplus Present in Sand Template (Line 2; Not to Exceed Line 3)0 5,207 6,892 3,062 Bluff Erosion 5 Net Contribution from Erosion of Bluff Face (pre-veg & during 4th tier const.; see Table 5)0 6,000 1,920 6 Adjusted Required Mitigation Volume (Line 1 - Line 4 - Line 5)18,744 7,537 12,022 17,772 7 Total Volume Delivered for Mitigation (see Line 9 in Table 2; Line 4 in Table 3; Line 8 in Table 4)23,951 14,429 15,085 TBI 8 Mitigation Surplus/Deficit ( Line 7 - Line 6 - Line 8)5,207 6,892 3,062 9 Total Volume Delivered for Geotube Construction (See Line 6 in Tables 2 and 4)12,653 0 2,931 0 10 Total Volume Delivered for Mitigation (see Line 11 in Table 2; Line 4 in Table 3; Line 8 in Table 4)23,951 14,429 15,085 TBI 11 Total Volume Delivered to Bluff Face (Not Counted as Mitigation; See Ln 10 in Tbl 2 & Ln 12 in Tbl 4)2,600 0 4,469 0 12 Total Volume Delivered by Truck (Sum Lines 10-12)39,204 14,429 22,485 TBI See Table 2 See Tables 3, 5 See Tables 4, 5 Base Required Mitigation Volume Mitigation Volume Adjustments Mitigation Volume Summary Sand Delivery Summary Page 2 of 4 Line Sand Delivery Amounts Cubic Yard (CY)/ Linear Foot (LF) Project Length (LF)Total CY 1 Inside Tier 2 Geotube 5 852 3,834 2 Inside Tier 3 Geotube 5 835 3,758 3 Bench Behind Tier 2 Geotube 3 852 2,556 4 Bench Behind Tier 3 Geotube 3 835 2,505 5 Total Sand For Geotube Construction (Sum Lines 1-4)12,653 6 Template on Top 22 852 18,744 7 Template at Ends 1,500 8 Sand Contributed to Littoral System During Construction 3,707 9 Total Mitigation Volume (Sum Lines 6-8)23,951 10 Total Volume Delivered to Bluff Face (Not Counted as Mitigation)2,600 11 Total Sand Delivered (Sum Lines 5, 9, and 10)39,204 Line Sand Delivery Amounts Cubic Yard (CY)/ Linear Foot (LF) Project Length (LF)Total CY 1 April 2014 7.1 852 6,015 2 Jan 2015 5.3 852 4,477 3 Feb 2015 4.6 852 3,936 4 Total Sand Delivered (Sum Lines 1-3)14,429 Table 2. Sand Delivered December 2013 - March 31, 2014 Geotube Construction Mitigation Volume Bluff Face Volume Total Sand Delivered Mitigation Volume Table 3. Sand Delivered April 1, 2014 - March 31, 2015 Page 3 of 4 Line Sand Delivery Amounts Cubic Yard (CY)/ Linear Foot (LF) Project Length (LF)Total CY Fourth Tier (3) 120' long x 45' circumference tubes (1) 75' long x 45' circumference tube Total of 435 linear feet Northern Returns (4) 25' long x 30' circumference tubes Total of 100 linear feet Northern Intermediate Returns(1) 35' long x 30' circumference tube (1) 45' long x 30' circumference tubeTotal of 80 linear feet Southern Returns (1) 65' long x 30' circumference tube (1) 70' long x 30' circumference tube(1) 75' long x 30' circumference tube (1) 80' long x 30' circumference tube Total of 290 linear feet Southern Intermediate Returns (1) 35' long x 30' circumference tube (1) 45' long x 30' circumference tube Total of 80 linear feet 6 Total Sand For Geotube 4th Tier and Returns Construction (Sum Lines 1-5)2,931 7 November and December 2015 (immediately post-construction)15,085 8 Total Mitigation Volume 15,085 9 Total Volume Delivered to Bluff for Vegetation (April 2015)3,418 10 Total Volume Delivered to Bluff to Fill Gully South of Viewing Area (Nov/Dec 2015)931 11 Total Volume Delivered to Bluff to Fill Gully at Viewing Area (Jan 2016)120 12 Total Volume Delivered to Bluff Face (Not Counted as Mitigation)4,469 13 Total Sand Delivered (Sum Lines 6, 8, and 12)22,485 2.0 80 160 2.0 2.0 290 5804 1 4.21 435 80 1831 2 2.0 100 200 160 Mitigation Volume Total Sand Delivered 5 Table 4. Sand Delivered April 1, 2015 - March 31, 2016 Geotube Construction - 4th Tier and Returns Bluff Face Volume (Not Counted as Mitigation) 3 Page 4 of 4 Table 5. Changes in Bluff Volume, July 2013 - April 2, 2016 Line Sand Delivery Amounts Total CY 1 Total Volume Delivered to Bluff Face (Dec 2013 - March 31, 2014; see Line 10 in Table 2)2,600 2 Total Volume Delivered to Bluff for Vegetation (April 2015; see Line 9 in Table 4)3,418 3 Total Volume Delivered to Bluff to Fill Gully South of Viewing Area (Nov/Dec 2015; see Ln 10 in Tbl 4)931 4 Total Volume Delivered to Bluff to Fill Gully at Viewing Area (Jan 2016; see Line 11 in Table 4)120 5 Total Volume Delivered to Bluff Face (Not Counted as Mitigation)7,069 6 Measured Change in Bluff Volume Above Geotube Sand Cover (2016 Bluff Volume - 2013 Bluff Volume)-851 Table 6. Bluff Volume Loss in Unprotected Areas Adjacent to Geotextile Tubes Line Area Volume Lost (CY)Length (Feet)Duration (Years) Erosion Rate (CY/LF/YR) 1 North Unprotected Area 31,329 800 2.75 14.2 2 South Unprotected Area 4,370 210 2.75 7.6 3 Total Bluff Erosion for Adjacent Unprotected Areas 35,699 1,010 2.75 12.9 Table 7. Summary of Sand Contribution in Cubic Yards (CY), December 2013 - March 31, 2016 Line Sand Amounts 12/13-3/31/14 4/1/14-3/31/15 4/1/15-3/31/16 1 Volume on Template at Start of Sand Year (Line 3 in Table 1)0 5,900 8,500 2 Total Volume Delivered for Mitigation (2015 and 2016: Line 7 in Table 1; 2014: Lines 6+7 in Table 2)20,244 14,429 15,085 3 Volume on Template at End of Sand Year (Line 3 in Table 1, using vol. on temp. at start of following yr)5,900 8,500 14,022 4 Total Volume Contributed from Sand Template 14,344 11,829 9,563 5 Total Volume Contributed from Sand Template (cy/lf/yr)16.8 13.9 10.1 6 Net Contribution from Erosion of Bluff Face (Line 5 in Table 1)0 6,000 0 7 Contribution from Construction (Line 8 in Table 2; Line 5 in Table 1)3,707 0 1,920 8 Total Volume Contributed 18,051 17,829 11,483 9 Total Volume Contributed in cy/lf/yr 21.2 20.9 12.1 10 Average Sand Contribution from 2013-2016 (cy/lf/yr)18.1 Construction Contribution Bluff Face Contribution Total Annual Sand Contribution Sand Added to Bluff Face (Dec 2013-3/31/2016) (Not Counted as Mitigation) Change in Bluff Volume (July 2013 - April 2, 2016) Template Sand Contribution Attachment B Supplemental Historical Analysis of Survey Data at Siasconset, Nantucket, MA Supplemental Historical Analysis of Survey Data at Siasconset, Nantucket, MA Prepared For: Siasconset Beach Preservation Association 18 Sasapana Road Nantucket, MA 02554 Prepared By: Woods Hole Group, Inc. 81 Technology Park Drive East Falmouth, MA 02536 December 2016 Supplemental Historical Analysis of Survey Data at Siasconset, Nantucket, MA December 2016 Prepared for: Siasconset Beach Preservation Association 18 Sasapana Rd Nantucket, MA 02554 Prepared by: Woods Hole Group 81 Technology Park Drive East Falmouth MA 02536 (508) 540-8080 Woods Hole Group, Inc. Supplemental Historical Analysis of December 2016 Survey Data at Siasconset, Nantucket, MA i 2000-0162-00 Siasconset Beach Preservation Association Table of Contents 1.0 INTRODUCTION ...................................................................................................1  2.0 LONG-TERM TRENDS ANALYSIS ON SHORELINE CHANGE, VOLUME CHANGE, AND BATHYMETRY .........................................................................1  2.1 SHORELINE CHANGE ................................................................................................ 3  2.2 CORRELATION BETWEEN BEACH VOLUME AND SHORELINE CHANGE ..................... 13  2.3 BATHYMETRIC CHANGE ........................................................................................ 16  3.0 ANALYSIS OF WADING SHOTS ......................................................................19  4.0 COMPARISONS TO OTHER MITIGATION REQUIREMENTS .................20  5.0 SUMMARY AND RECOMMENDATIONS .......................................................21  REFERENCES .................................................................................................................24  List of Figures Figure 1. Project Location and Profile Map. The Project Area is typically referred to as an area where shore protection projects have been located. ..............................2  Figure 2. Shoreline position at Profile 84 since 1994. ......................................................4  Figure 3. Shoreline position at Profile 90 since 1994. ......................................................5  Figure 4. Shoreline position at Profile 90.6 since 1994. ...................................................6  Figure 5. Shoreline position at Profile 91 since 1994. ......................................................7  Figure 6. Shoreline position at Profile 91.5 since 1994. ...................................................8  Figure 7. Shoreline position at Profile 92.5 since 1994. ...................................................9  Figure 8. Shoreline position at Profile 93 since 1994. ....................................................10  Figure 9. Shoreline position at Profile S since 1994. ......................................................11  Figure 10. Shoreline position at six (6) profiles within the geotube project area and immediately adjacent areas. .............................................................................11  Figure 11. Seasonality of shoreline change at Profile 84. .................................................12  Figure 12. Seasonality of shoreline change at Profile 91. .................................................13  Figure 13. Seasonality of shoreline change at Profile S. ...................................................13  Figure 14. Correlation between shoreline position and beach volume at Profile 84. ........15  Figure 15. Correlation between shoreline position and beach volume at Profile 91. ........15  Figure 16. Correlation between shoreline position and beach volume at Profile S. .........16  Figure 17. Bathymetry transects for Profile 84 since June 2008. ......................................17  Woods Hole Group, Inc. Supplemental Historical Analysis of December 2016 Survey Data at Siasconset, Nantucket, MA ii 2000-0162-00 Siasconset Beach Preservation Association Figure 18. Bathymetry transects for Profile 91 since June 2008. ......................................18  Figure 19. Bathymetry transects for Profile S since June 2008. .......................................18  Woods Hole Group, Inc. Supplemental Historical Analysis of 1 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association 1.0 INTRODUCTION The monitoring program at Siasconset provides a unique data set to characterize shoreline position, beach volume, and bathymetric change over time and space including over many years and along miles of the beach. The coverage over the years is unusually robust in that there have been sixty-nine (69) beach profile surveys since 1994. Figure 1 shows the forty-eight (48) beach profiles currently surveyed on a quarterly basis (yellow and red lines). Figure 1 also illustrates profiles that were surveyed in the past, but that were removed when new profiles (red lines) were added to focus on monitoring the performance of a geotube project installed between December 2013 and January 2014. The geotube project is permitted under Order of Conditions SE 48-2824, and is intended to manage erosion of the bluff between Profiles 90.9 and 91.9. Figure 1 demonstrates the similarly unusual robust coverage up and down the beach. The repeated beach profiles and overlapping bathymetry surveys extending offshore, afford the opportunity to gain clear insight on beach evolution and variability. To our knowledge, there are few if any other beach projects with this level of data collection over time and space. These data have been required by permit from the Conservation Commission and Mass DEP to monitor performance of shore protection projects intended to manage erosion at Siasconset. We have analyzed these data in various reports to assess the performance of shore protection and erosion control projects at Siasconset. These analyses focus on changes relative to conditions observed in the immediate prior survey, the prior year, the beginning of the period of performance (1994), or relative to some key event such as the installation of a shore protection project. The purpose of the reports is to aid in the understanding regional coastal processes, and the understanding of shoreline response to shore protection projects. Each report stands alone. The Siasconset Beach Preservation Fund (SBPF) also continued the surveys during time periods between active projects and permits to understand and quantify losses while advancing the overall understanding of coastal processes in the region. This memo presents three types of supplemental analyses including:  Long-term trends analysis on shoreline change, volume change, and bathymetry  Detailed analysis of wading water shots below mean low water  Comparisons to other known mitigation requirements in Massachusetts As such, it focuses on recent beach changes in the context of long-term trends and variability to gain further insight from these unique measurements made over a long time period and along a large area of beach. The memo also makes suggestions for future surveys, data analysis, and reporting refinements. 2.0 LONG-TERM TRENDS ANALYSIS ON SHORELINE CHANGE, VOLUME CHANGE, AND BATHYMETRY Survey data (collected since 1994) describing shoreline position, volume in the beach profile down to an elevation -5 ft below mean low water, and bathymetry were evaluated to lend additional insight on trends and variability. This additional work builds on Woods Hole Group, Inc. Supplemental Historical Analysis of 2 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association analysis presented at the 2013 Northeast Shore & Beach Preservation Association (NSBPA) in New Jersey (Buck, Leduc, and Hamilton, 2013). Figure 1. Project Location and Profile Map. The Project Area is typically referred to as an area where shore protection projects have been located. Woods Hole Group, Inc. Supplemental Historical Analysis of 3 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association 2.1 SHORELINE CHANGE Figures 2 through 9 illustrate cumulative change in shoreline position relative to a 1994 baseline position (zero on the vertical axis) against time on the horizontal axis. The figure captions include notes on profile-specific observations. A selected subset of eight (8) beach profiles represents the stretch of beach subject to monitoring including:  Near the south of the monitoring area (Profile 84)  Approximately 1,000 ft and 500 ft south of the geotubes (Profiles 90 and 90.6)  Within the geotube area (Profiles 91 and 91.5)  Approximately 500 ft and 1000 ft north of the geotubes (Profiles 92.5 and 93)  Near the north end of the monitoring area (Profile S) Individual data points on each plot represent the change in shoreline position at mean low water (MLW), based on the surveyed beach profile at that time. Positive numbers indicate shoreline advance and negative numbers indicate shoreline retreat relative to the 1994 baseline (assumed zero). On the figures, blue dots represent data obtained from surveys before the installation of geotubes. Brown dots represent data obtained from surveys obtained after the installation of geotubes. There is an underlying assumption in this color coding that monitoring data obtained from before and after the installation of geotubes (December, 2013 to January, 2014) may provide a test of whether the geotube installation affects changes in shoreline position. Based on the data presented below, the shoreline response since the geotubes were installed is not materially different from other shoreline responses measured in the past. However, the project provides a known geographic and temporal reference point, is subject to the current regulatory requirements, and is expected to be subject to future monitoring. The plots demonstrate the temporal variability and show:  Periods of stability when there is little cumulative change in shoreline position as seen in Figure 2 from December of 1996 to May of 2002;  Periods of shoreline advance as seen in Figure 2 from May 2002 to February, 2005; and  Periods of shoreline retreat as seen in Figure 3 from December, 1996 to February, 2005. General observations derived from the data plotted on Figures 2 through 9 are summarized below. Figure 10 also is included to illustrate time varying shoreline change for six (6) profiles within the geotube project area and immediately adjacent areas. This collection of long-term observations accentuates a conclusion that there is a high degree of variability, and that recent changes are similar to past observations:  Each profile includes times of shoreline advance and shoreline retreat, demonstrating a high degree of variability on short and long time scales. This high degree of variability, with observed short-term periods of erosion or accretion, suggests that adverse effects from the geotextile tubes could only be Woods Hole Group, Inc. Supplemental Historical Analysis of 4 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association reliably determined through the prevalence of sustained periods (2 years or more) of shoreline erosion exceeding historic observations.  Each profile responds differently on variable time scales.  This variability does not lend itself to fitting a long-term trend line with a high degree of statistical accuracy.  The current (August, 2016) shoreline position is generally similar (within about 20 feet) to the shoreline position in the ~2005-2008 timeframe, although there is substantial variability (up to 50 feet of cumulative difference) between these dates (which may be a result of short-term storm events, such as Hurricane Irene in August 2011 and Superstorm Nemo in February 2013).  The short-term variability shown by surveys since geotube installation in January 2014 is similar to short-term variability (~2-3 year periods) observed over many years of surveys before the geotubes were installed. Surveyed post-geotube shoreline changes are not materially different from previous observations as related to rates and duration of shoreline change. No accelerated erosion in excess of historical observations is evident.  Overall, the long-term plots of shoreline change provide more insight than the isolated time periods typically presented in the monitoring reports. Similar plots should be maintained and incorporated into the monitoring reports as appropriate. Figure 2. Shoreline position at Profile 84 since 1994.  Overall shoreline advance of ~130 ft since 1994  Relatively stable shoreline position from 1996 to late 2001  200 ft of shoreline advance from September 2001 to January 2004  Variable alternating periods of relative stability with modest shoreline advance and retreat spanning multiple years since 2004 Woods Hole Group, Inc. Supplemental Historical Analysis of 5 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association  Current shoreline position similar to 2008; an observation also noted for other profiles  Recent trend of shoreline advance since October 2014; similar periods of shoreline advance on the order of 30 ft also experienced from October 2008 to March 2012 and from February 2005 to August 2006 Figure 3. Shoreline position at Profile 90 since 1994.  Variable periods of shoreline retreat, stability, and advancement  Net shoreline erosion on the order of -120 ft since 1994  Relatively consistent erosion from 1996 through April 2001;  Sharper short-term shoreline retreat between June 2005 and February 2006  Shoreline advance from February 2006 to November, 2007  Substantial reversing trend of beach accretion from April 2011 to April 2014  Current shoreline position similar to 2007; an observation common to other profiles  Recent trend of shoreline retreat since April 2014; similar to the rate experienced from September 1998 to December 2001 Woods Hole Group, Inc. Supplemental Historical Analysis of 6 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 4. Shoreline position at Profile 90.6 since 1994.  Variable periods of shoreline erosion, stability, and accretion  General trend of shoreline erosion between 1996 and 2003  Substantial advance from October 2003 to February 2005  Sharp retreat from 2005 to 2006  Net shoreline retreat on the order of -100 ft since 1994  Recent trend of shoreline erosion since April 2014; similar periods experienced previously in 1998-2000 and 2005-2006  Current shoreline position similar to 2007; an observation common to other profiles Woods Hole Group, Inc. Supplemental Historical Analysis of 7 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 5. Shoreline position at Profile 91 since 1994.  Net shoreline loss since 1994 on the order of -110 ft  Substantial trend of beach erosion at variable rates through 2007  Variable shoreline position since 2005 with reversing trends of beach accretion and erosion  Substantial shoreline advance from September 2012 to March 2013  Little net change in the shoreline position since April 2007; similar to other profiles  Current trend of beach retreat since September 2013  Similar shoreline erosion measured also in September 2010 to September 2012, October 2003 to June 2005, and December 1998 to June 2000 Woods Hole Group, Inc. Supplemental Historical Analysis of 8 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 6. Shoreline position at Profile 91.5 since 1994.  Net shoreline retreat on the order of -75 ft since 1994  Relatively consistent long-term shoreline erosion from 1996 through September 2012; with short-term variability  Substantial beach accretion occurred from September 2012 to March 2013  Current shoreline position similar to December 2006; the observation that the current shoreline position is similar to the condition 8-10 years ago is common to other profiles  Recent trend of beach accretion since October 2015 Woods Hole Group, Inc. Supplemental Historical Analysis of 9 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 7. Shoreline position at Profile 92.5 since 1994.  Highly variable shoreline position  Net erosion on the order of -50 ft since 1994  Current shoreline position almost identical to December 2006; similar to other profiles  Recent trend of beach accretion since October 2015 Woods Hole Group, Inc. Supplemental Historical Analysis of 10 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 8. Shoreline position at Profile 93 since 1994.  Relatively stable shoreline position since 1998  Majority of net losses occurred between 1994 and 1998  Current shoreline position similar to the envelope between April 2004 and December 2006  Recent short-term variability in the shoreline position similar to past short-term variations Woods Hole Group, Inc. Supplemental Historical Analysis of 11 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 9. Shoreline position at Profile S since 1994.  Net shoreline advance on the order of 30 ft since 1994  Majority of accretion occurred up to 2007  Relatively stable but variable shoreline position since 2007; as with other profiles, the current shoreline position is almost identical to 2006 Figure 10. Shoreline position at six (6) profiles within the geotube project area and immediately adjacent areas. Woods Hole Group, Inc. Supplemental Historical Analysis of 12 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association  High degree of variability  Recent (post-geotube installation) changes in shoreline position are similar to past observations  No evidence of any accelerated erosion post-geotube installation exceeding historical observations To further investigate short-term variability in the shoreline position, a seasonal analysis of the shoreline position was conducted to determine if particular times of year are more indicative of overall shoreline change. The analysis depended on graphical visualization of the data because statistical analysis again showed no statistically meaningful indications of seasonal trends. Figures 11 through 13 provide example plots of the same data as shown on Figures 2, 5, and 9 for Profiles 84, 91, and S, each with a different symbol used for surveys during the four seasons of the year. Based on these graphics, trends and variability are similar regardless of season. Annual and longer term trends would be resolved with surveys once or twice per year. Quarterly sampling and observation does not inform the analysis to any greater degree. Figure 11. Seasonality of shoreline change at Profile 84. Woods Hole Group, Inc. Supplemental Historical Analysis of 13 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 12. Seasonality of shoreline change at Profile 91. Figure 13. Seasonality of shoreline change at Profile S. 2.2 CORRELATION BETWEEN BEACH VOLUME AND SHORELINE CHANGE A volume change analysis revealed similar trends and observations as indicated for the shoreline change analysis in Section 2.1. A complication of the volume change analysis, Woods Hole Group, Inc. Supplemental Historical Analysis of 14 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association however, exists for profiles that experienced substantial erosion landward of the original benchmarks and landward survey limits established in 1994. As explained in the quarterly survey reports, volume change between recent surveys can be computed where the survey limits have been extended farther landward. Volume change calculations from older surveys cannot be extended father landward because the survey data do not exist. Thus, volume change estimates compared to older surveys are underestimated because the recently active profile extends farther landward than the original survey limits. Once the current profile erodes to the point where no sand remains above -5 ft MLW within the originally surveyed beach profile extent, there is no additional volume left to erode; thus, by comparing only to the original survey “window,” volume change will be zero by definition. A correlation analysis between the shoreline change and the volume change in the beach profile provided an alternate method for gauging beach volume response for each survey since 2002. Figures 14 through 16 illustrate this correlation for the same three (3) representative profiles presented in Figures 11 through 13. There is a strong linear relationship between these two quantities, and many of the correlations are similar to the relationship in Profile 84. This shows that shoreline position may provide a reliable indicator of beach volume change. From a statistical perspective, R2 values for the best fit lines through the shoreline position versus beach volume curves are typically 0.8 or greater with some exceeding 0.9. Given the complications of calculating consistent beach volumes, and with drawing reliable comparisons to past data sets, emphasis should be placed on collecting reliable shoreline position data. Future surveys may be made more efficient by focusing exclusively on shoreline position instead of volume change. As shown by the examples for Profiles 91 (offset linear relationships pre- and post-geotube, likely due to the sand volume in the tubes which effectively adds sand to the profile) and S (where there is more variability), the relationship does not always hold. We do not recommend changing the survey focus at this time; however, this will be monitored in the coming surveys. Woods Hole Group, Inc. Supplemental Historical Analysis of 15 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 14. Correlation between shoreline position and beach volume at Profile 84. Figure 15. Correlation between shoreline position and beach volume at Profile 91. Woods Hole Group, Inc. Supplemental Historical Analysis of 16 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 16. Correlation between shoreline position and beach volume at Profile S. 2.3 BATHYMETRIC CHANGE Since 1994, water depth (bathymetry) measurements have been collected by extending the beach profiles offshore. Surveys were typically conducted once per year, and twice per year at times including recently. The bathymetry surveys are conducted by boat, and are intended to overlap the land-based beach surveys requiring navigating very close to the shoreline. They surveys also extend between 2,500 and 3,500 ft offshore, or to the - 25 or -35 ft MLW depths. Having repeated bathymetric surveys of the same region over a long time frame also is unique. Figures 17 through 19 provide representative sample plots of the repeated bathymetry surveys for Profiles 84, 91, and S. General observations include:  The bathymetry offshore Siasconset features a generally stable profile, particularly in the northern and central portions of the monitoring area. This is represented by the examples for Profiles S and 91.  Some areas, such as shown by the example for Profile 84, and for other profiles in the southern portion of the monitoring region, have been subject to large-scale, dynamic shoal features. These features are captured by annual bathymetric profiles, and lend insight to the regional coastal processes for planning purposes.  Variability exists in the bathymetry both due to natural bedform movements, small scale seafloor features, and as a result of the survey methods and repeatability. The small scale features (e.g., cobbles or boulders) may not always be detected along a surveyed profile depending upon the actual vessel path, which can readily vary by tens of feet due to difficulties of navigating in the coastal zone offshore Nantucket. Vertical accuracy also depends upon a variety of factors Woods Hole Group, Inc. Supplemental Historical Analysis of 17 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association related to the echosounder, movement of the vessel, tides, and waves. All of these factors collectively introduce survey variability as well related to accuracy, precision, and repeatability. For these reasons, differences of less than 1 ft cannot be distinguished.  Although the bathymetry data are valuable for understanding local geomorphology and shoal movements/migration, the data are not suitable to detect thin layers of sand coverage and transport within the cobble habitat. The sand layers are likely relatively thin compared to the cobble and/or boulder sizes. Distinguishing natural sand movements and migrations from the transport of mitigation sand quantities also introduces challenges with interpreting the data. Figure 17. Bathymetry transects for Profile 84 since June 2008. Woods Hole Group, Inc. Supplemental Historical Analysis of 18 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association Figure 18. Bathymetry transects for Profile 91 since June 2008. Figure 19. Bathymetry transects for Profile S since June 2008. Woods Hole Group, Inc. Supplemental Historical Analysis of 19 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association 3.0 ANALYSIS OF WADING SHOTS A wading shot in this context refers to data point collected in the water by a wading surveyor. These data points are collected while doing the land-based beach profile surveys, but require a different survey method and equipment. The wading shots require a rod man adequately equipped to swim in the water, and a survey rod capable of withstanding the conditions. Each individual survey point can take several attempts as the rodman finds safe footing in the surf, and as a surveyor with a transit on the beach gains a visual fix on the survey rod. Land-based shots alternatively can be collected rapidly in seconds each using only the RTK roving equipment. Given the relative importance of the shoreline position per the analysis above, and these difficulties associated with obtaining shore-based wading shots below the water line, an investigation of the information provided by data collected below 0 ft MLW was conducted. This work builds on the analysis by Woods Hole Group in the Baseline Erosion Rates Report published in July 2002. Using the shore-based beach profile data, the volume of sand between 0 ft and -5 ft MLW was calculated from the data for the last five (5) years between April 2011 and May 2016. On average the data showed that ~4 cy/ft of sand resides in the profiles between these depths. This volume translates to an average of just under 6% of the sand in the profile. Alternate approaches were then evaluated to estimate the volume of sand in the profiles below 0 ft MLW. Based on the prior work in the Baseline Erosion Rates Report, a linear extrapolation technique was preferred to approximate the beach profile shape below 0 ft MLW. This method was then applied to each data set dating back to April 2011. Volume calculations using the extrapolation technique, essentially assuming no wading shots were actually surveyed below 0 ft MLW, were compared to volumes calculated using the full data set including the wading shots. The average difference in the volume of sand estimated for each profile was 1.1 cy/ft, which equates to a 1.4% difference. Thus, whether or not the wading shots are surveyed translated to a very small difference in the overall estimate of the sand volume in each profile. Using the profile volume estimates, the total volume in the beach can be calculated for stretches of the shoreline spanned by adjacent profiles. This calculation was applied to estimate the total sand volume in the beach along the area protected by the geotubes (from Profiles 90.9 to 91.9) for each survey in the past 5 years. The total sand volume varied between a low of 21,732 cy in September 2013 to a high of 60,243 cy in October 2014, with an average of 43,103 cy of sand. Total beach sand volume also was calculated using all of the survey data, including the wading shots, and for a subset of the data not using the wading shots; instead using the extrapolation technique. The difference in total volume using the two methods was small compared to the total volume, and ranged from -3,820 cy to 1,855 cy with an average difference of -552 cy. Negative values corresponded to surveys when the extrapolation technique underestimated the total volume of sand, and positive values indicate when the extrapolation technique overestimated to the total sand volume. The volume differences between the two methods are relatively small compared to the total sand volume, as well Woods Hole Group, Inc. Supplemental Historical Analysis of 20 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association as the variability and change in sand volume between surveys. The calculated volume differences between the two methods also are small when compare to the sand mitigation quantity, which is ~18,000 cy/yr. Based on this analysis, and the apparent importance of measuring the shoreline position per the analysis above, it is important to ensure the beach profile surveys extend to the MLW shoreline; however, full surveys down to -5 ft MLW do not provide a substantial improvement. Considering that the surveys can be completed in approximately half the time if there are no wading shots, there are potential efficiency improvements when planning around sometimes brief weather, wave, tide, and daylight windows. The time spent traversing the beach during bird nesting season could potentially be reduced, and the risk exposure to swimming surveys (particularly during the winter) can also be reduced without a significant decrease in data utility. 4.0 COMPARISONS TO OTHER MITIGATION REQUIREMENTS A key aspect of the overall monitoring and mitigation program is the sand mitigation quantity, which approaches 20,834 cy/yr. We understand this volume was estimated based on long-term estimates of bluff erosion rates and volumes plus a 50% factor of safety along with special conditions related to regular observations, post-storm reviews, and requirements to maintain a certain level of geotube coverage. Based on the analysis above, there are no major changes in the performance of the beach since the geotubes were installed that have not been observed previously. Generally, there have not been apparent adverse effects, and the trends in the beach performance since installation of the geotubes are similar to trends that occurred historically prior to installation of the project. Although the documented natural variability at the site precludes a purely quantitative statistical measure of project performance and impacts (since the natural variability is large), the data indicate the influence of the project is not significant and/or the associated mitigation is effectively helping to maintain the coastal system. For comparison purposes, background research was conducted to compile sand mitigation requirements for other projects known to Woods Hole Group in the Commonwealth. A selection of ten (10) projects were identified that have Orders of Conditions with a sand mitigation requirement, including two (2) on Nantucket, one (1) on Marthas Vineyard, and seven (7) on Cape Cod. These projects span a time horizon between 1986 and 2016, and include hard and soft engineering solutions spanning shoreline reaches of between 100 ft and 1,800 ft with annual sand mitigation requirements between 65 and 1,100 cubic yards of sand per year. As with the condition at Siasconset, a volume was estimated in most cases based upon an average shoreline, bank or bluff erosion rate, height and length of shoreline protected. Implementation strategies (i.e., when and how to place the sand) varied, and included a simple annual nourishment when possible, a frontloaded strategy with some number of years deposited initially during construction, and/or a monitoring-based decision process. Although the methods are similar, two key differences with Siasconset are: 1) Scale of the mitigation volume – the height of the bluff at Siasconset, combined with its erosion rate and length of project produce a relatively large quantity of sand as compared to other projects. Woods Hole Group, Inc. Supplemental Historical Analysis of 21 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association 2) Factor of safety – the Siasconset calculated volume is unique with its 50% factor of safety applied to the sand volume, which alone is larger than the sand requirement for the other projects researched. If continued monitoring indicates the shoreline continues to respond in a manner consistent with historical observations, and that the sand quantity is sufficient to ensure continued performance of the project, than the results may be utilized to manage the mitigation sand quantity. 5.0 SUMMARY AND RECOMMENDATIONS Supplemental data analysis was performed on the beach profile survey data at Siasconset. The analysis included:  Long-term trends analysis on shoreline change, volume change, and bathymetry  Detailed analysis of wading water shots below mean low water  Comparisons to other known mitigation requirements in Massachusetts The analysis characterized recent beach changes in the context of long-term trends and variability to gain further insight from these unique measurements made over a long time period and along a large area of beach. The memo also makes suggestions for future surveys, data analysis, and reporting refinements. Key findings resulting from the supplemental analysis are:  Long-term shoreline change exhibits a high degree of variability on short and long time scales. There were no statistically meaningful trends that can be generally applied to the shoreline change data. In spite of the variability, the present shoreline is similar to the shoreline position 8 to 10 years ago. Recent shoreline change since the geotubes were installed is profile-specific, and exhibits similar patterns observed in the past. The data indicate the influence of the geotube project is not significant and / or the associated mitigation is effectively helping to maintain the coastal system. Overall, the shoreline change long-term trend plots provide better insight to the local processes, and are recommended as part of the regular survey reports.  The shoreline change data were analyzed for different seasons to identify seasonal trends. Analysis was focused to determine whether surveys at certain times of the year were more insightful or represented a more stable, worst-case, or other notable beach conditions. This analysis did not reveal meaningful seasonal variability; trends and variability are similar regardless of the season. The lack of consistent seasonal influence likely results from the highly variable wave climate, episodic severe storm influences from hurricanes and northeasters, influence of bluffs, relatively steep beach profile, and unique tidal current regime. A maximum of twice per year beach profile surveys would be sufficient. This also is consistent with the monitoring suggestions in the MassDEP Beach Nourishment Best Practices Guide (MassDEP, 2007), which suggest seasonal surveys for a year Woods Hole Group, Inc. Supplemental Historical Analysis of 22 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association or so, followed by annual surveys for monitoring beach nourishment projects. The National Research Council also recommends a similar approach to beach profile monitoring, which suggests reducing the frequency of surveys over time (National Academy Press, 1995). To be consistent with standard engineering practice, which typically is focused on capturing an eroded “winter” profile along with a recovered “summer” profile after more quiescent periods, if there will be two surveys per year, one survey is recommended in late winter / early spring and the other is recommended in late summer. These surveys also would be consistent with and comparable to long-term data.  A strong correlation exists between the shoreline position and the volume of sand in the profile. Consideration should be given to focusing the surveys on simply locating the shoreline. This has the potential to improve overall efficiency without losing meaningful information.  The bathymetry offshore Siasconset features a generally stable profile, particularly in the northern and central portions of the monitoring area (which includes the geotextile tubes). Bathymetry data are helpful for general scientific purposes to understand regional coastal processes (e.g., offshore shoal movements and evolutions), but are not conclusive for determining whether the geotextile tubes are having an adverse impact upon adjacent beaches. Shoreline position data are most useful for that purpose. Bathymetry surveys conducted a maximum of once per year are sufficient to characterize regional morphology. In addition, fewer transects could be surveyed (particularly in the northern portion of the monitoring area) without sacrificing information to understand the regional processes. Reducing the total number of bathymetry survey profiles to ~22 that extend no more than 3,000 ft offshore would potentially allow for the survey to be completed in a single calm sea/weather day without sacrificing substantive information. To provide useful data for present and long-term comparisons, the subset of ~22 profiles would include the historic whole number profiles 81 through 99 plus profiles Q, S, and W. Additionally, it is proposed that bathymetry monitoring be re-evaluated annually to assess its continued value.  Wading shots below the low water line and down to -5 ft MLW have been collected traditionally, but analysis indicates the incremental value in collecting these data is minimal. Updated analysis indicates beach volume can be extrapolated from the shoreline to -5 ft MLW. Associated errors are small compared to the overall sand volume, and substantially less than the sand mitigation amounts. Surveys to the MLW shoreline provide sufficient data to calculate beach volume and to examine time-varying shoreline trends to gauge overall beach change, including influences of shore protection projects such as the geotubes. Practically, removing a requirement for wading shots would add tremendous flexibility to completing the surveys in timely fashion, and also reduce inherent risks to the survey crew. Woods Hole Group, Inc. Supplemental Historical Analysis of 23 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association  The beach response since the geotubes were installed is similar to past measured shoreline changes. These data suggest that the mitigation sand volume required can be reduced to offset the long-term sand volume erosion rate in the project area. A review of other shore protection projects in the Commonwealth that include special conditions for sand mitigation suggests the factor of safety applied to estimating the mitigation volumes for Siasconset is uniquely conservative and requires a larger sand volume relative to long-term erosion rate as compared to other projects. Woods Hole Group, Inc. Supplemental Historical Analysis of 24 December 2016 Survey Data at Siasconset, Nantucket, MA 2000-0162-00 Siasconset Beach Preservation Association REFERENCES Buck, Mitchell A., Elise Leduc, and Robert Hamilton. 2013. Twenty Years of Shoreline Change at Siasconset, MA. Northeast Shore and Beach Preservation Association. MassDEP. 2007. Beach Nourishment MassDEP’s Guide to Best Management Practices for Projects in Massachusetts. National Academy Press. 1995. Beach Nourishment and Protection. Committee on Beach Nourishment and Protection; Marine Board; Commission on Engineering and Technical Systems; National Research Council. 334 pp. Figure A-1 October 2016 Beach Contours at Profiles 90 through 93 Sconset Geotextile Tube Project Nantucket, Massachusetts Vertical Datum is MLW92 Figure A-2 October 2016 Enlarged Beach Contours at Profiles 90 through 91.35 Sconset Geotextile Tube Project Nantucket, Massachusetts Vertical Datum is MLW92 Figure A-3 October 2016 Enlarged Beach Contours at Profiles 91.35 through 93 Sconset Geotextile Tube Project Nantucket, Massachusetts Vertical Datum is MLW92 Attachment C 2016 Wetland Wells Groundwater Level Monitoring 2016 WETLANDS WELLS GROUNDWATER LEVEL MONITORING Baxter Road, Nantucket DEP File No. SE48-2824 October 2016 Prepared by: Epsilon Associates 3 Clock Tower Place Suite 250 Maynard, MA 01754 978-897-7100 Prepared for: Siasconset Beach Preservation Fund P.O. Box 2279 Nantucket, MA 02584 21597/Sconset Beach 2 Wetland Wells Monitoring Report Sconset Beach Preservation Fund Epsilon Associates, Inc. WETLAND WELLS MONITORING REPORT 1.0 Introduction The Sconset Beach Preservation Fund (SBPF) is permitted under SE48-2824 to install geotextile tubes at the base of the bluff and a catch basin at 91 Baxter Road. As part of the Order of Conditions (SE48-2824) for the geotextile tube project, thrice annual monitoring of water levels within the wetlands is required, as described in Special Condition 50 of the Project’s Order of Conditions: 50. Groundwater levels within the Bordering Vegetated Wetlands adjacent to the drainage system and Baxter Road shall be taken at the beginning, middle and end of the growing season to determine if the drainage system is having an adverse impact to the vegetated wetlands. If there is a change in groundwater deemed significant by the Commission they may call for the discontinuation or removal of the system. In order to fulfill permit requirements and assess whether the vegetated wetlands are impacted by the project, water levels within the wetlands are being monitored. On June 28, 2016, three monitoring wells were installed along the western side of Baxter Road (monitoring wells E-2, E-4, and E-6R; see attached Figure 1). Well E-2 is located between wells E-4 and E-6R and is positioned west of Baxter Road, midway along the eastern side of 90 Baxter Road’s parcel boundary. Well E-4 was installed at 94 Baxter Road (north of the catch basin) and Well E-6R is at 86 Baxter Road (south of the catch basin). Well locations were chosen to be consistent with historic groundwater well monitoring locations to the greatest extent feasible given site constraints. The well locations were reviewed with Conservation Commission staff prior to installation. 2.0 Groundwater Level Monitoring Methodology Water levels in the monitoring wells are measured using a small-diameter water level indicator probe. The probe cable is marked in 0.01-foot increments and the depth to water level is measured to the nearest hundredth of a foot and recorded on-site. 3.0 Results Table 1 details the results of well monitoring conducted on June 28, 2016, July 28, 2016, and September 12, 2016. Water level readings are presented as depths (where the depth is measured from the top of the monitoring well). 21597/Sconset Beach 3 Wetland Wells Monitoring Report Sconset Beach Preservation Fund Epsilon Associates, Inc. Table 1. Wetland Wells Groundwater Level Monitoring June 28, 2016 July 28, 2016 September 12, 2016 Well Top Elevation Water Level Depth (ft) Top Elevation Water Level Depth (ft) Top Elevation Water Level Depth (ft) E-2 79.08 8.28 79.08 6.82 79.08 9.15 E-4 79.12 8.15 79.12 7.93 79.12 9.25 E-6R 77.54 9.60 77.54 8.90 77.54 10.79 In all three wells, water levels were slightly higher in July than in June, and then water levels dropped in September compared to July. A review of rainfall data for Nantucket indicates that May precipitation was 3 inches, June precipitation was 2.11 inches, July precipitation was 4.42 inches, August precipitation was 1.2 inches, and September precipitation was 3.6 inches (about 1.5 inches fell prior to the September well reading). The trends in the water level data appear to correlate with the rainfall data: water levels were the highest at the end of July (after the highest amount of precipitation in July), and water levels were lowest in early September after low August precipitation). 4.0 Discussion Groundwater levels in the wetlands were monitored on over 50 occasions during a 6-year period from 2001-2007. During this 6-year monitoring period, water levels were noted to vary by about 2 to 5 feet in each individual well over the course of the monitoring period. During the three months of wetland monitoring in 2016, water levels in each individual well varied by about 1-2 feet. Such variation is within the range of expected variation and appears to correlate with precipitation data. Accordingly, there is no evidence of harm to water levels in the wetland from the installation of the catch basin. No further monitoring is recommended. %2 %2 %2 8586 87 97 90 83 92 82 81 79 93 91 84 77 75 80 96 78 98 94 82A 100 E-4 E-6R BAXTER ROADSANKATY ROAD97 101 103 107 111 93 7 E-2 Figure 1Monitoring Well Locations and MassDEP Wetlands Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA Data Source: Office of Geographic Information (MassGIS), Commonwealth of Massachusetts, Information Technology Division LEGEND Basemap: 2014 Orthoimagery, MassGIS %2 Monitoring Well Location Parcel Boundary MassDEP Data (January 2009) Hydrologic Connection Wetland G:\Projects\Lighthouse\2014\installed_drainage_wells_20160328.mxd °0 75 150 Feet1 inch = 150 feetScale1:1,800 Attachment D Intertidal Benthic Invertebrate Sampling, Sconset Bluff Geotextile Project, MA CR Environmental, Inc. 639 Boxberry Hill Rd. East Falmouth, MA 02636 Ph/fax 508-563-7970 www.crenvironmental.com 1 MEMORANDUM Date: November 3, 2016 To: Maria Hartnett, Epsilon Associates, Maynard, MA From: J. Ryther/C. Cogswell, CR Environmental, Inc., E. Falmouth, MA Re: Intertidal Benthic Invertebrate Sampling, Sconset Bluff Geotextile Project, MA On August 16-18, 2016, CR Environmental, Inc. (CR) of East Falmouth, MA collected twelve benthic grab samples from four areas within the intertidal zone of Siasconset Beach, Nantucket, Massachusetts for Epsilon Associates (Figure 1). The four sampling zones included the Project Area (91, 91.2, 91.5) in the vicinity of the geotubes, south of Codfish Park (82, 83, 84), between the Project Area and Hoick’s Hollow (93, 94, 95) and north of Hoick’s Hollow (96, 96.5, 97). The study site has direct exposure to the Atlantic Ocean and the beach is a very high energy environment. The purpose of the benthic grab sampling effort was to evaluate if the intertidal benthic invertebrates closest to the geotubes were markedly different than those found to the north and south of the Project Area. Methods Samples were collected in the intertidal zone at low tide by a two-man team, and the sample coordinates recorded using an IX Blue sub-meter GPS. An 8-inch x 8-inch aluminum frame was inserted into the substrate at the designated sampling locations, and all of the material in the frame removed down to approximately four inches below the mud line. The resulting volume sampled was approximately one gallon for each of the two samples. The sampler footprint (0.04 m2) and volume is equivalent to that taken by a Ted Young benthic grab, the standard grab used extensively for subtidal studies in the New England area. The sediment samples were sieved, and preserved on-site using a 10% formalin solution. Samples were then transferred to 70% alcohol and delivered to AMA’s laboratory in Magnolia, MA to document the presence and abundance of invertebrate species. At AMA’s laboratory the samples were stained with rose bengal which dyes the organism’s protein pink making them easier to detect. CR Environmental, Inc. 639 Boxberry Hill Rd. East Falmouth, MA 02636 Ph/fax 508-563-7970 www.crenvironmental.com 2 While no grain size analyses were performed for each benthic sample, the residue after screening through a 1 mm sieve was used to give an approximation of the sediment type. The volume of material remaining after 1 mm sieving was compared to the sample volume prior to sieving. The missing material would be smaller than 1 mm. Results There was no fine material such as silt/clay or very fine sand visible in the intertidal sediment samples before sieving. Sediments were of a coarse texture due to wave action, and the median grain size at each sampling station likely changes somewhat with the season or due to storms. Sediment grain size was finer at the Project Area (Stations 91, 91.2, and 91.5), and more southerly stations (Stations 82, 83 and 84 south of Codfish Park). The majority ~95-99% of the sediment at these stations passed through a 1 mm aperture sieve and the dominant grain size was likely in the medium to coarse sand range (Table 1). In contrast, at the more northerly sampling stations the dominant grain size was predominantly very coarse sand and gravel. Fifteen to 75% of the material did not pass through a 1 mm sieve at Stations 93, 94, 95 between the Project Area and Hoick’s Hollow, and at Stations 96, 96.5 and 97, north of Hoick’s Hollow. The high energy environment of Siasconset Beach is reflected in the faunal results. Only eight species were found in this harsh environment, and with the exclusion of the mole crab Emerita and the beach flea Talorchestia, only single specimens of the six other species were found (Table 2). All of the species are types of crustaceans commonly found in sandy intertidal environments (i.e. amphipods, skeleton shrimp, hooded shrimp, mole crabs, isopods). Organisms in samples within the Project Area were not markedly different from those found to the north or south. Species number (richness) within the Project Area ranged from 1 to 3. At other sampling sites species richness ranged from 0 at Station 97 to the north of Hoick’s Hollow to 4 at Station 93 between the Project Area and Hoick’s Hollow. Mole crabs were the dominant species at all locations. Individuals of the megalopa stage of the mole crab Emerita megalothalma were present in significant numbers in the three samples within the Project Area and south. One hundred and thirteen (113) individuals were found at Station 84 south of Codfish Park; and twenty eight (28) CR Environmental, Inc. 639 Boxberry Hill Rd. East Falmouth, MA 02636 Ph/fax 508-563-7970 www.crenvironmental.com 3 at Station 91, thirteen (13) at Station 91.5 and eleven (11) at Station 91.2 within the Project Area. These sites had sand as the median sediment type rather than gravel. The variation in density and absence/low abundance of Emerita in samples at other southerly sandy stations (82 and 83) is typical of the contagious (clumped) distribution of this species. At the coarser-grained more northerly intertidal sampling stations mole crab abundance was generally lower ranging from 0 to 8 individuals (Table 1). Mole crabs are crustaceans of the intertidal zone. This species is very mobile, and moves up and down the tidal zone with changing tides. After reproduction the species goes through several planktonic zoeal phases before settling in the intertidal zone as megalopae. Several weeks later they molt into juveniles and then adults. Adults feed by burrowing backwards into the sand holding antennae above the surface to filter plankton out of the passing water. When a mole crab is exposed as waves wash over a burrowed individual it can re-bury itself in about 1.5 seconds in an attempt to avoid predation. The species is believed to be a source of food for some species of birds and fish. It is not uncommon to find megalopa stages of this species in the intertidal areas in September. The low density and diversity of marine fauna in the various samples from Siaconset Beach is not surprising given the coarse sediments. Tidal and wave action continuously moves the intertidal sediments providing a very hostile environment for marine fauna. The continual movement and reworking of sediments hinders the establishment of most species. There was no evidence of harm to intertidal invertebrates in the Project Area, proximate to the geotubes, compared to the other sampling stations. In addition, no representatives of a resource species were found at any of the twelve sampling stations. Additional monitoring may not be warranted given the low species diversity, low abundance and lack of noteworthy species found within the sandy intertidal beach habitat of Siaconset Beach. TABLE 1. Estimate of Sediment Sample Grain Size – Benthic Invertebrate Samples Sconset Bluff Geotextile Tube Project (reference Figure 1 for sample locations) Station Percentage volume compared to non-sieved sample (approximate)1 South of Codfish Park 82 < 1% 83 < 1% 84 < 1% Project Area 91 < 5% 91.2 < 5% 91.5 < 5% Between Project Area and Hoick’s Hollow 93 20% 94 50% 95 75% North of Hoick’s Hollow 96 33% 96.5 50% 97 15% NOTES: 1 Those samples with a higher % of sediment retained following sieving are coarser grained. TABLE 2. SUMMARY OF INTERTIDAL BENTHIC INVERTEBRATE DATA - Sconset Bluff Geotextile Tube Project, Nantucket, MA - August 2016 Sample Number SPECIES 82 83 84 91 91.2 91.5 93 94 95 96 96.5 97* South of Codfish Park Within Project Area Between Project & Hoick's Hollow North of Hoick's Hollow Amphipoda Corophidae sp. (juv.)1 Lysianassidae sp. (juv.)1 Parametopella cypris 1 Talorchestia megalopthalma 1 1 Caprellidae Caprella penantis 1 Cumacea Cumacea sp. (juv.)1 Decapoda Emerita talpoida (megalopa stage)1 113 28 11 13 1 4 8 1 1 Isopoda Edotia montosa 1 SPECIES RICHNESS 2 1 1 2 1 3 4 1 1 1 1 0 * No organisms found at sample station 97. !. !. !. !. !. !.!. !. !. !. !. !. !. 97 96-5 91-5 93 94 95 96 91 91-2 84 82 83 340000 340000 342000 342000 344000 344000 346000 346000 348000 348000 350000 350000 352000 352000 354000 354000 356000 35600094000 940009700097000100000100000103000103000106000106000109000109000112000112000Benthic SamplesSiasconset Beach, Nantucket, MA NOTES:1) Survey conducted 8/17/20162) GridMassachusetts State Plane NAD 83 Feet 0 1,400 2,800 Feet : Figure 1 Name X Y WGS84_Lat WGS84_Lon 82 346889.6 93179.32 41.25449519 N 69.96580749 W 83 347338.28 94221.11 41.25734677 N 69.9641524 W 84 347722.71 95204.08 41.26003798 N 69.96273216 W 91 347886.85 102167.05 41.2791449 N 69.96197799 W 82 346892.51 93179.54 41.25449575 N 69.9657969 W 91-2 347838.05 102342.08 41.2796261 N 69.96215157 W 91-5 347722.19 102674.77 41.28054113 N 69.96256556 W 93 347267.88 103878.21 41.28385166 N 69.96419129 W 94 346878.38 104804.75 41.28640112 N 69.9655876 W 95 346532.4 105511.04 41.28834536 N 69.9668306 W 96 345796.86 107124.56 41.29278601 N 69.96947091 W 96-5 345396.27 108037.04 41.295297 N 69.97090828 W 97 345128.33 108605.22 41.29686084 N 69.97187068 W Attachment E Sconset Beach Underwater Video Survey Report Submitted to: Nantucket Conservation Commission 2 Bathing Beach Road Nantucket, Massachusetts 02554 Submitted by: Siasconset Beach Preservation Fund P.O. Box 2279 Nantucket, Massachusetts 02584 October 26, 2016 Sconset Beach Underwater Video Survey Report Prepared by: Epsilon Associates, Inc. 3 Clock Tower Place, Suite 250 Maynard, Massachusetts 01754 CR Environmental, Inc. 639 Boxberry Road East Falmouth, Massachusetts 02536 Nantucket, MA October 26, 2016 Nantucket Conservation Commission 2 Bathing Beach Road Nantucket, MA 02554 Subject: Sconset Beach Underwater Video Survey Report File No. SE 48-2824, Sconset Bluff Geotextile Tube Project, Nantucket, MA Dear Commissioners: On behalf of the Siasconset Beach Preservation Fund (SBPF), Epsilon Associates, Inc. is pleased to submit the Sconset Beach Underwater Video Survey Report to the Nantucket Conservation Commission. The enclosed report has been prepared in compliance with the Final Order of Conditions Special Condition #28, pursuant to the Town of Nantucket Wetlands Protection Bylaw, Chapter 136: 28. Photographs and/or video shall be taken along the transects within the project area and the area directly adjacent to the project area. The underwater video shall be able to characterize the bottom sediments, species present and relative abundance including the calculating of the percent cobble where appropriate. If you have any questions regarding this application, please contact us at 978-618- 7447 or lsmith@epsilonassociates.com (Les Smith) or 703-489-8945 or mhartnett@epsilonassociates.com (Maria Hartnett). Sincerely, EPSILON ASSOCIATES, INC. Lester B. Smith, Jr. Maria B. Hartnett Principal Associate Encl. PRINCIPALS Theodore A Barten, PE Margaret B Briggs Michael E Guski, CCM Dale T Raczynski, PE Cindy Schlessinger Lester B Smith, Jr Robert D O’Neal, CCM, INCE Andrew D Magee Michael D Howard, PWS Douglas J Kelleher AJ Jablonowski, PE Stephen H Slocomb, PE David E Hewett, LEED AP Samuel G. Mygatt, LLB 1943-2010 ASSOCIATES Dwight R Dunk. LPD David C. Klinch, PWS, PMP 3 Clock Tower Place, Suite 250 Maynard, MA 01754 www.epsilonassociates.com 978 897 7100 FAX 978 897 0099 Sconset Beach Underwater Video Survey Report Nantucket, MA Submitted to: Nantucket Conservation Commission Submitted by: Siasconset Beach Preservation Fund Prepared by: Epsilon Associates, Inc. CR Environmental, Inc. October 26, 2016 Table of Contents 21597/Sconset Geotextile Tube Project i Table of Contents Underwater Video Survey Report Epsilon Associates, Inc. Table of Contents UNDERWATER VIDEO SURVEY REPORT 1 1.0 Introduction 1 2.0 Vessel Operations, Navigation, and Survey Design 1 3.0 Survey Data Acquisition and Processing 2 4.0 Survey Results 4 4.1 Biota 4 4.2 Bottom Sediment Coverage 5 5.0 Conclusions 7 ATTACHMENT A Video Survey Maps Figure 1 Underwater Video Trackline Map Figure 2 Percent Cobble/Boulder Present at Trackline Intersections Figure 3 Percent Cobble Present at 2007 Survey Stations ATTACHMENT B Video Survey Screenshot Figures #1-35 Transect Intersect Points ATTACHMENT C Shore-Perpendicular Transect Screenshots (Representative Biota) TR-91.13 TR-91.35 TR-91.9 Underwater Video Survey Report 21597/Sconset Geotextile Tube Project 1 Underwater Survey Report Epsilon Associates, Inc. UNDERWATER VIDEO SURVEY REPORT 1.0 Introduction On June 15, 2016, CR Environmental, Inc. (“CR”) and Epsilon Associates, Inc. (“Epsilon”) on behalf of the Siasconset Beach Preservation Fund (“SBPF”) conducted underwater video surveys offshore from the geotube project site at the base of the bluff from 87-105 Baxter Road, Nantucket, MA. These geotextile tubes were installed in December 2013 and January 2014 (with an approximate length of 852-feet) and were then expanded in November and December 2015 to a total length of 947-feet. As part of the Order of Conditions (SE48-2824) for the geotextile tube project, underwater video monitoring is required as described in Special Condition 28 of the Project’s Order of Conditions: 28. Photographs and/or video shall be taken along the transects within the project area and the area directly adjacent to the project area. The underwater video shall be able to characterize the bottom sediments, species present and relative abundance including the calculating of the percent cobble where appropriate. The purpose of the underwater video survey monitoring is to evaluate if the mitigation sand (the “sand template”) placed on top of the geotextile tubes is causing a significant alteration or loss of cobble/boulder habitat located directly offshore of the geotextile tubes. The June 2016 survey marks the first underwater video survey since the geotextile tubes were installed. This document describes the data acquisition and processing methods, equipment used on the survey, and survey results. 2.0 Vessel Operations, Navigation, and Survey Design The underwater video monitoring survey activity was conducted from the 35 ft fishing vessel Althea K. The vessel was configured to accommodate navigation and video acquisition systems and was furnished with a portable generator to power survey electronics. The survey crew on the underwater video survey consisted of a boat captain and mate, a field biologist, an oceanographic technician, and an environmental scientist. . Seven shore-parallel video drift transects were conducted to visually characterize bottom sediments, biota, and type of bottom cover offshore from the geotube project site (see the maps in Attachment A). These transects started approximately 220 feet from the Mean Low Water (MLW) line and extended 1,900 feet offshore. A transect was attempted 40-50 feet offshore but due to excessive floating algae in the water the line was abandoned. The shore-parallel transects are referred to by their distance offshore, in feet: TR-220, TR-370, TR-720, TR-1,020, TR-1,280, TR-1,580, and TR-1,900. Three shore-perpendicular video drift transects, which crossed the shore-parallel transects, were also conducted just offshore from the geotextile tubes. These three shore-perpendicular video drift transects were 21597/Sconset Geotextile Tube Project 2 Underwater Survey Report Epsilon Associates, Inc. conducted in approximately the same location as three previously-established shoreline survey transects that are regularly surveyed by the Woods Hole Group. Accordingly, these three video drift transects are referred to by the same name as the shoreline survey transects (TR-91.13, TR-91.35, and TR-91.9). Navigation for the survey was accomplished using a Hemisphere VS-110 12-channel sub- meter (GPS) system. The GPS system was interfaced to a laptop computer running HYPACK 2013A hydrographic survey software. HYPACK recorded vessel position, water depth, and provided a steering display for the vessel captain. The video drift transects were created in HYPACK and background imagery was imported from a shape file showing the Woods Hole Group Shoreline Monitoring Program survey transects. 3.0 Survey Data Acquisition and Processing Underwater video operations were conducted using a real time high resolution color underwater video data acquisition system permitted the characterization of bottom habitat and the species present. Maps showing the location of the video transects offshore are provided in Attachment A. Underwater video data was collected with CR’s portable towed video sled consisting of a lightweight aluminum frame, Outland Technologies’ high-resolution low light color camera, and two wide-angle 250 watt lights with variable output control. The video camera was cabled to the surface to an OTI-960 DVR recorder and topside monitor. As a back-up video system, a GoPro Hero 4+ Black video camera in a Nimar deep water housing was mounted above the OTI camera and programed to record HD video at 1080P, 30 frames per second, and 12 megapixel still frames every 10 seconds. The video sled was lowered by hand and the height of the system off the bottom was continually adjusted to achieve the best bottom coverage and video quality. The video system was operated in “drift and tow mode” and the vessel speed varied between 0.5 to 2 knots. Mounted lasers on the video sled frame were used for scaling purposes, and a calibrated scale template was overlain on the video frame or screen captures. The distance between template grid lines in both the X and Y directions was equal to approximately 6 inches. This grid system permitted scaling and estimating of bottom biota and determining substrate classes and their percent coverage. When the video camera was one foot off the bottom, the viewing area of the camera was approximately 1.5 ft x 1.5 ft (18” x 18”) and the video quality was optimal for bottom sediment characterizations and biota identifications. HYPACK navigation files were recorded during each video drift. Video data were transferred to a processing computer and viewed by a staff scientist at Epsilon. Representative screen captures (frame images) were extracted along each video transect to characterize bottom sediments and biota offshore from the project. 21597/Sconset Geotextile Tube Project 3 Underwater Survey Report Epsilon Associates, Inc. To analyze the bottom characteristics of each transect, screenshots were taken at each intersection between the seven shore-parallel and three shore-perpendicular transects. In addition, coordinates for two previously-established, shore-perpendicular survey transects (90.6 and 92.5) were added to the figure, then screenshots were pulled from intersections between those two transects and the seven shore-parallel transects. No underwater video surveys occurred along shoreline survey lines 90.6 and 92.5. Using the GPS data collected simultaneously with the video, the coordinates for each of these intersections were extracted into a spreadsheet (Table 1). The intersection coordinates were found in the video by scrolling through the video until the live latitude and longitude reading matched as closely as possible to the GPS data coordinates. Sometimes the view closest to the intersection point was not optimal due to the camera position being either too far or too close to the bottom. In these instances a screenshot was captured as close as possible to the intersect position where the view was improved. Due to the resolution of the main video feed, the GoPro footage was matched side-by-side to the main video and screenshots were extracted from the GoPro’s higher quality camera. The GoPro screenshots showed a wider field-of-view than the low-resolution video, so these GoPro intersection screenshots were adjusted to closely match the scale of the main video’s view. The scale grid was overlain on the portion of the GoPro video view where it matched the main video’s view. Live video (not shown) was reviewed concurrent with the screenshots for the most accurate assessment of biota and bottom substrate. Once the scale grid was in place, the bottom coverage was classified along a gradient of grain sizes using the Auster hierarchical approach (Auster 1998). Bottom sediment and habitat types within the offshore area included: flat sand, sand ripples, sand waves, pebble, cobble, and boulder. The percent cover for bottom sediment types present in each screenshot was approximated using the scale grid. Each of the nine grid sections was reviewed and bottom sediment was categorized individually, then an average was calculated for the complete screenshot. The percent bottom type numbers were rounded to the nearest five percent for presentation in Table 1. Due to rounding, the sum of the addends in the table does not always equal 100 percent and may range from 95-105 percent. To maintain consistency across the 35 screenshots, the same individual performed all percent cover estimates. Each screenshot is given three identifiers. First, the intersection location is indicated by the name of the transect, which is the same as the distance in feet from the shore. Second, the shore-perpendicular transect that crosses the shore-parallel transect is listed. Lastly, each screenshot is given a number in order of the time the screenshot was taken within the transect video (for #1-21), where points run from north to south and switch to the next transect offshore after every three points. For example, points 1-3 are ordered north to south on transect TR-220, points 4-6 are ordered north to south on transect TR-370, and so on. Screenshots #22-35 were taken from the intersections between the new shore-parallel 21597/Sconset Geotextile Tube Project 4 Underwater Survey Report Epsilon Associates, Inc. transects and the two previously-established shoreline survey shore-perpendicular transect lines (90.6 and 92.5). 4.0 Survey Results Table 1 provides the bottom sediment coverage and biota present in the underwater video survey transects taken in June 2016 offshore from the sand nourishment project site. Results of each screenshot are tabulated in terms of bottom sediment coverage percentages and biota. Screenshots 1-21 were taken at intersections between new transects, while screenshots 22-35 used shore-perpendicular transect locations taken from the previously- established shoreline monitoring. Table 1 provides an assessment of the biota present and the bottom type at each of the 35 screenshot locations. 4.1 Biota During the underwater video survey, twelve invertebrate species, four fish species, and five marine plant and algal species were observed. The dominant biota across all transects included unidentified branching brown algae, unidentified branching red algae, bread crumb sponge, black sea bass, and common skate. Additional biota observed at the transect intersections were rock crab, scup, common skate, unidentified shells, common slipper shells, Irish moss red algae, rock weed brown algae, common barnacles, northern star coral, and orange encrusting bryozoan. Additionally, while not captured in the screenshots, the following biota were also observed during the video survey fieldwork: unidentified branching hydroid, invasive white tunicate, sand sponge, red dulse red algae, black sea bass, striped bass, hermit crab, horseshoe crab, and spider crab. • Branching brown and red algae were abundant and were observed in the entire survey area. • Bread crumb sponge was abundant and was found in the four transects farthest offshore: TR-1020, TR-1280, TR-1580, and TR-1900. • Black sea bass, rock crab, scup, and common skate were common fish in most of the survey area. Sea bass and skates were the most abundant species over the whole survey area and were observed mostly in the offshore cobble/boulder habitats. • Floating red algae was common mostly in the nearshore transects TR-220, TR-370, TR-720, and TR-1020. • Common slipper shells were common in the entire survey area. 21597/Sconset Geotextile Tube Project 5 Underwater Survey Report Epsilon Associates, Inc. • Bryozoans were not very abundant and were found in TR-1280 and TR- 1900. • Star coral was not very abundant at the transect intersections and was found in TR-220 and TR-1900. In addition to the intersection screenshots mentioned above, additional screenshots were reviewed to assist in the identification of biota. These additional screenshot images are included in Attachment C. 4.2 Bottom Sediment Coverage In addition to biota, Table 1 lists the bottom coverage types observed in the survey area. The bottom sediment categories include flat sand, sand waves, sand ripples, pebble, cobble, and boulder. An additional category shows the cobble and boulder percent coverage combined into one percentage. These percentages were combined in order to show a more representative picture of the bottom substrate differences across the seven shore-parallel transects. This combined data was used to create Figure 2, which interpolated the abundance of cobble/boulder present, in relation to the transect intersections, in order to visualize the percentages across the survey area. The percentage of cobble/boulder coverage ranges from green gradient colors (0-25%), to blue gradient colors (25-70%), and finally red gradient colors (70-100%) (Figure 2). The percent cobble/boulder coverage varies significantly across the survey area, from <10% to 90%. Most of the survey area had 25-55% cobble coverage. In general, the northern nearshore survey area has lower cobble/boulder percent coverage than the southern or farther offshore survey areas. Closest to shore in the northern portion of the survey area, the percent cobble/boulder percentage is lowest. The percent cobble/boulder habitat broadly increases farther offshore. The highest amount of cobble/boulder habitat is located at three distinct areas located 1,000 or more feet offshore, which are at intersections 11, 33, and 35. This general trend of the percentage of cobble/boulder habitat increasing with distance offshore is expected based on the results of past surveys conducted prior to geotextile tube construction. Overall, the underwater video survey indicated that a productive habitat area is located just offshore from the geotextile tubes, and there is no indication that such habitat is being covered by the sand mitigation. The results of the 2016 survey were compared with a previous survey done in a similar area in 2007. A comparison between the 2007 and 2016 survey was attempted; however, several caveats should be noted. • The 2007 survey was conducted and analyzed using slightly different methodology than the 2016 survey. Notably, different sample points were analyzed in the 2007 survey than in the 2016 survey and then the results were interpolated in GIS to 21597/Sconset Geotextile Tube Project 6 Underwater Survey Report Epsilon Associates, Inc. generate a map of the bottom coverage over the entire survey area. The 2016 survey includes data collected closer to shore than the 2007 survey. • The 2007 survey was focused on mitigation of impacts and accordingly very conservatively counted all material other than sand as “hard bottom” or “cobble bottom.” In contrast, the 2016 survey is focused on analyzing bottom coverage type through time and accordingly utilizes a standard geological classification scheme of pebbles, cobbles, and boulders, with only the combined cobble and boulder percentages being mapped. The 2016 approach of mapping cobbles and boulders is consistent with the 2009 Ocean Management Plan, which identified areas of “hard/complex seafloor” as consisting of “1) areas of exposed bedrock or concentrations of boulder, cobble, or other similar hard bottom distinguished from surrounding unconsolidated sediments, 2) a morphologically rugged seafloor characterized by high variability in bathymetric aspect and gradient, or 3) man- made structures, such as artificial reefs, wrecks, or other functionally equivalent structures that provide additional suitable substrate for development of hard bottom biological communities.” The guidance in the 2009 Ocean Management Plan regarding hard/complex seafloor was not available at the time of the 2007 report. • Nearly a decade has elapsed between the 2007 and 2016 surveys. Given the very significant storm activity in the area, as well as known offshore shoal movement, it is highly likely that the bottom composition has experienced some change over the last decade due to naturally occurring events. In particular, bathymetric monitoring since 1994 has demonstrated that, within a few thousand feet of the shoreline in the vicinity of the geotextile tubes, bottom elevations can vary annually by several feet due to regional sand or shoal movements. Despite these caveats, the comparison between the two figures shows that most of the 2007 and 2016 survey areas include 25-70% cobble/boulder. The 2016 survey shows lower cobble/boulder closer to shore; this effect is likely at least partially due to the fact that the 2016 survey includes transects closer to shore (TR-220 and TR-370), whereas the 2007 survey started at about 700 feet offshore and then results were interpolated shoreward. The 2016 survey shows a higher percentage of cobble in the middle of the survey area located about 1,000 feet or more directly offshore from the geotextile tubes. Much of the variation between the two survey results is anticipated to be the result of natural variability. A review of bathymetry in the Project area from 2008-2013 (just after the 2007 survey to just prior to the installation of the geotextile tubes) indicates that bathymetric elevations varied by several feet between the two surveys due to natural conditions. Likewise, bathymetry in the Project area recorded during surveys from 2014-2016 (the period after the geotextile tube installation) are within the historic range of values. When the underwater video results and bathymetry are considered together, there is no indication that the sand cover on the geotextile tubes is covering cobble/boulder bottom. 21597/Sconset Geotextile Tube Project 7 Underwater Survey Report Epsilon Associates, Inc. 5.0 Conclusions An underwater video survey of the area located just offshore of the geotextile tubes and surrounding areas was conducted in June 2016, approximately 2.5 years after the installation of geotextile tubes at the base of the bluff. During this survey, twelve invertebrate species, four fish species, and five marine plant and algal species were observed. The dominant biota across all transects included branching brown algae, branching red algae, and bread crumb sponge. Black sea bass, rock crab, scup, and common skate were common in most of the survey area. The bottom sediment type was also surveyed. The percent cobble/boulder coverage varies significantly across the survey area, from <10% to >90%. Most of the survey area had 25-55% cobble coverage, with localized areas of higher or lower coverage. Based on the continued prevalence of cobble/bottom habitat located directly offshore of the geotextile tube Project, there is no evidence that cobble/boulder habitat is being covered by the mitigation sand. While additional monitoring is required be performed this fall to evaluate conditions subsequent to the initial June 2016 survey, the results of the survey suggest that less frequent monitoring would be appropriate. A review of historic bathymetry in the area indicates that bottom elevations in the area a few thousand feet offshore of the geotextile tubes can vary annually by several feet due to regional sand or shoal movements. These natural sand and shoal movements are far more significant than the small volume of the mitigation sand template. The small volume of the sand template is illustrated by the following calculation, which considers an extremely unlikely scenario: if the entire sand template volume of 20,834 cubic yards washed directly offshore in a small area (to be conservative, this area was assumed to be 1,000 feet alongshore [the length of the geotextile tubes] by 1,600 feet offshore [the approximate distance to the depth of closure]), with no sand transport to the north or south and no transport farther offshore, the depth of coverage would be about four inches. Even considering this extremely unlikely scenario, the potential impact to offshore bathymetry from the sand template is minimal compared to natural bathymetric variability and therefore would neither be harmful nor clearly discernible. Underwater video monitoring could only generate meaningful information in the event that regular monitoring indicates that the sand mitigation template is contributing several times more sand than the unprotected bluff. Page 1 of 2 Flat Sand/Sand Waves/Sand Ripples Pebble Cobble Boulder Cobble/ Boulder TR-220 91.9 1 7:35 6:42 65 15 20 0 20 Shells, Branching Red Algae, Rock Weed Brown Algae TR-220 91.35 2 9:52 8:59 100 0 0 0 0 Rock Crab, Brown Algae TR-220 91.13 3 11:25 10:33 95 0 5 0 5 Common Barnacles on Rock TR-370 91.9 4 12:32 9:14 55 0 0 45 45 Irish Moss Red Algae, Branching Brown and Red Algae, Floating Red Algae TR-370 91.35 5 15:12 11:55 85 0 0 15 15 Branching Brown and Red Algae TR-370 91.13 6 0:39 (Part 2 Video)15:06 30 5 15 45 60 Shells, Branching Brown and Red Algae TR-720 91.9 7 8:57 8:09 85 15 0 0 0 Shells, Brown Algae, Branching Red Algae TR-720 91.35 8 11:17 10:28 45 0 10 45 55 Branching Brown and Red Algae TR-720 91.13 9 13:31 12:42 25 5 45 20 65 Branching Brown Algae TR-1020 91.9 10 6:46 5:59 15 25 60 0 60 Shells, Branching Brown Algae, Bread Crumb Sponge TR-1020 91.35 11 8:48 8:01 0 5 25 65 90 Shells, Branching Brown and Red Algae TR-1020 91.13 12 10:15 9:28 10 25 70 0 70 Branching Brown and Red Algae TR-1280 91.9 13 7:14 6:13 10 30 60 0 60 Common Skate, Shells, Branching Brown Algae, Bryozoan TR-1280 91.35 14 9:14 8:13 15 60 25 0 25 Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-1280 91.13 15 10:38 9:37 20 10 60 10 70 Shells, Irish Moss Red Algae, Branching Brown and Red Algae, Bread Crumb Sponge TR-1580 91.9 16 5:43 5:13 45 15 40 0 40 Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-1580 91.35 17 7:53 7:23 20 55 30 0 30 Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-1580 91.13 18 9:17 8:47 40 20 40 0 40 Common Skate, Shells, Branching Brown and Red Algae TR-1900 91.9 19 8:20 5:27 40 0 0 60 60 Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-1900 91.35 20 9:57 7:04 10 55 35 0 35 Common Slipper Shells, Branching Brown Algae, Bread Crumb Sponge, Northern Star Coral TR-1900 91.13 21 11:25 8:31 35 35 30 0 30 Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-220 92.5 22 5:04 4:12 80 0 0 20 20 Shells, Branching Brown and Red Algae, Rock Crab TR-370 92.5 23 8:54 5:37 100 0 0 0 0 Branching Brown Algae, Floating Red Algae TR-720 92.5 24 6:19 5:30 80 5 15 0 15 Common Slipper Shells, Irish Moss Red Algae, Branching Brown and Red Algae TR-1020 92.5 25 4:16 3:29 5 60 40 0 40 Shells, Branching Brown and Red Algae, Bread Crumb Sponge Table 1. Sconset Beach Video Survey - Bottom Sediment Coverage and Biota Shore- Parallel Transect # Shore- Perpendicular Transect # Screenshot Label GoPro Time Split Video Time Bottom Sediment Coverage Biota Page 2 of 2 Flat Sand/Sand Waves/Sand Ripples Pebble Cobble Boulder Cobble/ Boulder Shore- Parallel Transect # Shore- Perpendicular Transect # Screenshot Label GoPro Time Split Video Time Bottom Sediment Coverage Biota TR-1280 92.5 26 4:56 3:56 20 30 50 0 40 Shells, Branching Brown and Red Algae TR-1580 92.5 27 3:41 3:11 40 40 20 0 20 Shells, Branching Brown and Red Algae TR-1900 92.5 28 6:17 3:24 20 50 30 0 30 Rock Crab, Scup, Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-220 90.6 29 14:27 13:35 40 35 0 30 30 Shells, Branching Brown and Red Algae, Northern Star Coral TR-370 90.6 30 6:23 (Part 2 Video)20:49 50 15 40 0 40 Shells, Branching Brown and Red Algae TR-720 90.6 31 0:05 (Part 2 Video)17:00 15 30 55 0 55 Common Slipper Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-1020 90.6 32 13:56 13:09 20 40 35 0 35 Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-1280 90.6 33 13:43 12:41 10 10 40 40 80 Shells, Branching Brown and Red Algae, Bread Crumb Sponge TR-1580 90.6 34 12:06 11:35 65 25 15 0 15 Branching Brown and Red Algae, Bread Crumb Sponge TR-1900 90.6 35 14:17 11:23 5 5 35 50 85 Shells, Branching Brown and Red Algae, Bread Crumb Sponge, Northern Star Coral, Orange Encrusting Bryozoan Attachment A Video Survey Maps Figure 1 Underwater Video Trackline Map Figure 2 Percent Cobble/Boulder Present at Trackline Intersections Figure 3 Percent Cobble Present at 2007 Survey Stations 92.5 90.6 TR-91.9 TR-91.35 TR-91.13 TR-720TR-1,280 TR-1,580 TR-370TR-220 TR-1,900 TR-1,020 18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 21 20 19 242322 25 G:\Projects\Lighthouse\2016\Underwater_Video_Transects20160816_external.mxd Figure 1Underwater Video Trackline Map Sconset Beach Video Survey Nantucket, Massachusetts Data Source: Office of Geographic Information (MassGIS), Commonwealth of Massachusetts, Information Technology Division LEGEND Basemap: 2013 Orthophotography, MassGIS °0 375 750 Feet1 inch = 750 feet Scale1:9,000 Transect Survey Point Intersection Video Drift Transects Shoreline Survey Transects Geotube Area NorthAtlantic Ocea n 26 27 28 29 30 31 32 33 34 35 Note: -Transects 92.5 and 90.6 were not video drift transects and were added to the figure so that coordinates could be pulled-The NAD27 Datum was used for consistency with Woods Hole Group Shoreline Surveys Basemap: 2013 Orthophotography, MassGIS TR-91.9 TR-91.35 TR-91.13 TR-220 TR-370 TR-720 TR-1,020 TR-1,280 TR-1,580 TR-1,900 N orth A t la n ti c Oc e an18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 21 20 19 343332313029 35 272625242322 28 G:\Projects\Lighthouse\2016\Percent_Cobble_Boulder_20161012.mxd Figure 2Percent Cobble/Boulder Present at Trackline Intersections Sconset Beach Video Survey Nantucket, Massachusetts Data Source: Office of Geographic Information (MassGIS), Commonwealth of Massachusetts, Information Technology Division LEGEND 0 350 700 Feet1 inch = 700 feet Scale1:8,400 Screenshot Location Video Drift Transects Shoreline Survey Transects Geotube Area % Cobble/Boulder 0-10% 10-25% 25-40% 40-55% 55-70% 70-85% 85-100% 90.6 Note: -The NAD27 Datum was used for consistency with Woods Hole Group Shoreline Surveys 92.5 27 73 39 57 40 50 98 47 45 44 43 52 51 59 60 58 28 29 42 41 32 30 31 G:\Projects\Lighthouse\2016\Percent_Cobble_Boulder_2007.mxd Figure 3 Percent Cobble Present at 2007 Survey Stations Sconset Beach Video Survey Nantucket, Massachusetts Data Source: Office of Geographic Information (MassGIS), Commonwealth of Massachusetts, Information Technology Division LEGEND Basemap: 2013 Orthophotography, MassGIS °0 250 500 Feet1 inch = 500 feet Scale 1:6,000 2007 Survey Stations2007 Survey % Cobble 0-10% 10-25% 25-40% 40-55% 55-70% 70-85% 85-100% NorthAtlanticOcean Attachment B Video Survey Screenshot Figures #1-35 Transect Intersect Points 1 (Flat Sand 50%, Pebble 5%, Cobble 25%, Boulder 20% ) Shells, Branching Red Algae, Rock Weed Brown Algae 2 (Sand Waves 100%) Rock Crab, Brown Algae 3 (Sand Ripples 95%, Pebbles 5%) Common Barnacles on Rock 4 (Flat Sand 30%, Boulder 70%) Irish Moss Red Algae, Branching Brown and Red Algae, Floating Red Algae 5 (Flat Sand 80%, Boulder 20%) Branching Brown and Red Algae 6 (Flat Sand 50%, Pebble 5%, Cobble/Boulder 45%) Shells, Branching Brown and Red Algae 7 (Sand Ripples 90%, Pebble 10%) Shells, Brown Algae, Branching Red Algae 8 (Flat Sand 50%, Pebble 5%, Cobble 5%, Boulder 40%) Branching Brown and Red Algae 9 (Flat Sand 25%, Pebble 15%, Cobble/Boulder 60%) Branching Brown Algae 10 (Flat Sand 15%, Pebble 30%, Cobble 55%) Shells, Branching Brown Algae, Bread Crumb Sponge 11 (Flat Sand 5%, Boulder 95%) Shells, Branching Brown and Red Algae 12 (Flat Sand 30%, Pebble 30%, Cobble 40%) Branching Brown and Red Algae 13 (Flat Sand 20%, Pebble 30%, Cobble 50%) Common Skate, Shells, Branching Brown Algae, Bryozoan 14 (Flat Sand 20%, Pebble 70%, Cobble 10%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 15 (Flat Sand 30%, Pebble 10%, Cobble 45%, Boulder 15%) Shells, Irish Moss Red Algae, Branching Brown and Red Algae, Bread Crumb Sponge 16 (Flat Sand 40%, Pebble 30%, Cobble 30%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 17 (Flat Sand 20%, Pebble 60%, Cobble 20%? ) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 18 (Flat Sand 40%, Pebble 10%, Cobble 50%) Common Skate, Shells, Branching Brown and Red Algae 19 (Flat Sand 45%, Boulder 55%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 20 (Flat Sand 15%, Pebble 75%, Cobble 10%) Common Slipper Shells, Branching Brown Algae, Bread Crumb Sponge, Northern Star Coral 21 (Flat Sand 35%, Pebble 50%, Cobble 15%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 22 (Flat Sand 80%, Boulder 20%) Shells, Branching Brown and Red Algae, Rock Crab 23 (Flat Sand 100%) Branching Brown Algae, Floating Red Algae 24 (Sand Ripples 85%, Pebble 5%, Cobble 10%) Common Slipper Shells, Irish Moss Red Algae, Branching Brown and Red Algae 25 (Flat Sand 5%, Pebble 65%, Cobble 30%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 26 (Flat Sand 40%, Pebble 20%, Cobble 40%) Shells, Branching Brown and Red Algae 27 (Flat Sand 45%, Pebble 35%, Cobble 20%) Shells, Branching Brown and Red Algae 28 (Flat Sand 15%, Pebble 70%, Cobble 15%) Rock Crab, Scup, Shells, Branching Brown and Red Algae, Bread Crumb Sponge 29 (Sand Ripples 50%, Pebble 20%, Boulder 30%) Shells, Branching Brown and Red Algae, Northern Star Coral 30 (Flat Sand 45%, Pebble 15%, Cobble 40%) Shells, Branching Brown and Red Algae 31 (Flat Sand 25%, Pebble 40%, Cobble 35%) Common Slipper Shells, Branching Brown and Red Algae, Bread Crumb Sponge 32 (Flat Sand 10%, Pebble 60%, Cobble 30%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 33 (Flat Sand 10%, Pebble 10%, Cobble 35%, Boulder 45%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge 34 (Flat Sand 80%, Pebble 10%, Cobble 10%) Branching Brown and Red Algae, Bread Crumb Sponge 35 (Pebble 10%, Cobble 50%, Boulder 40%) Shells, Branching Brown and Red Algae, Bread Crumb Sponge, Northern Star Coral, Orange Encrusting Bryozoan Attachment C Shore-Perpendicular Transect Screenshots (Representative Biota) TR-91.13 TR-91.35 TR-91.9 TR-91.13 (Page 1 of 4) TR-91.13 (Page 2 of 4) TR-91.13 (Page 3 of 4) TR-91.13 (Page 4 of 4) TR-91.35 (Page 1 of 3) TR-91.35 (Page 2 of 3) TR-91.35 (Page 3 of 3) TR-91.9 (Page 1 of 4) TR-91.9 (Page 2 of 4) TR-91.9 (Page 3 of 4) TR-91.9 (Page 4 of 4) Attachment F Drainage System Monitoring 20 Mary Ann Drive • Nantucket, MA 02554 508-825-5053 • www.NantucketEngineer.com December 5, 2016 Maria Hartnett, Associate Epsilon Associates, Inc. 3 Mill & Main Place, Suite 250 Maynard, Massachusetts 01754 RE: SBPF - Baxter Road Drainage System Monitoring Dear Maria: We have been monitoring the function of the stormwater drainage system near 87 Baxter Road, in accordance with the Stormwater Operation and Maintenance Plan. The system appears to be functioning as designed, and we do not have any immediate concerns. There is approximately four-inches of accumulated sediment in the base of the catchbasin, which is below the threshold for cleaning. We will continue to monitor the system. There is some sediment along the gutter line of Baxter Road which we recommend be swept and removed from the area. Please feel free to contact me with any questions or concerns regarding this matter. Sincerely, Nantucket Engineering & Survey, P.C. By: Arthur D. Gasbarro, PE, PLS, LEED AP CC: Josh Posner, SBPF Attachment F Response to Comments on Annual Report (dated May 2, 2017) PRINCIPALS Theodore A Barten, PE Margaret B Briggs Michael E Guski, CCM Dale T Raczynski, PE Cindy Schlessinger Lester B Smith, Jr Robert D O’Neal, CCM, INCE Andrew D Magee Michael D Howard, PWS Douglas J Kelleher AJ Jablonowski, PE Stephen H Slocomb, PE David E Hewett, LEED AP Dwight R Dunk, LPD David C. Klinch, PWS, PMP Samuel G. Mygatt, LLB 1943-2010 ASSOCIATES Richard M. Lampeter, INCE Maria B. Hartnett Geoffrey Starsiak 3 Mill & Main Place, Suite 250 Maynard, MA 01754 www.epsilonassociates.com May 2, 2017 Nantucket Conservation Commission 2 Bathing Beach Road Nantucket, MA 02554 Subject: Response to Comments on Annual Report SE48-2824, Sconset Bluff Geotextile Tube Project Dear Commissioners: The following document presents responses from the Sconset Beach Preservation Fund to the memo to Jeff Carlson from Greg Berman dated April 7, 2017. Following these responses, we have also provided a response to the comments provided by Applied Coastal on behalf of the Nantucket Land Council in a memo dated April 12, 2017. We look forward to discussing the Annual Report with the Commission at the May 22, 2017 meeting. Sincerely, EPSILON ASSOCIATES, INC. Maria B. Hartnett Associate 21597/Sconset 1 Response to Third Party Review Epsilon Associates, Inc. RESPONSE TO THIRD PARTY REVIEW This report presents responses from the Sconset Beach Preservation Fund to the memo to Jeff Carlson from Greg Berman dated April 7, 2017. This report is organized to follow the order of Mr. Berman’s letter. Comments excerpted from his letter are presented in italicized text followed by responses in plain text. This document includes the following attachments that are referenced in our responses and that were previously provided to the Conservation Commission (Attachments A-D), as well as a supplemental analysis included as Attachment E: • Attachment A: November 1, 2013 Epsilon Memo “Baxter Road Geotube Project – Coastal Bank Retreat Calculations” • Attachment B: Explanation of Tidal Datum Used for Siasconset Beach Dewatering Project Per Leo Asadoorian, PLS, Blackwell & Associates, Inc.; March 23, 2004 • Attachment C: Southeast Nantucket Beach Monitoring 71st Survey Report, prepared by Woods Hole Group, March 2017 • Attachment D: 2001-2007 Wetland Well Monitoring Data • Attachment E: Bank Retreat Calculations for North and South Control Areas 2.1 Sand Delivery - Response to Comments “Additionally, some bluff erosion (6,000 cy in 4/1/14-3/31/15 and 1,920 cy in 4/1/15- 3/31/16) was added into the mitigation volume. Unless this volume was entirely replaced on the bluff it should not be counted as mitigation, and it is difficult to determine if/when it was replaced…If these volumes do not qualify as mitigation the summary mitigation volumes would look like the table below [which shows a deficit of sand].” We believe some clarification will assist with this comment. The Sand Report tracks all sand delivered for the Project, including sand for mitigation, sand for construction, and sand that was placed on the bluff face to smooth out deep rills and gullies prior to the planting of vegetation. The Sand Report indicated that sand placed on the bluff face was not counted as mitigation if it remained on the bluff face and was not available to the littoral system. During the construction of the fourth tier, however, when the third tier of geotextile tubes had to be exposed to allow placement of the fourth tier, much of the previously-placed sand slumped down off the bluff and was available to the littoral system. This component of the sand was then counted as part of the mitigation. As noted in the June 2016 Sand Delivery Report, “Since the purpose of the mitigation volume is to replicate that amount of sand that would have eroded from the bluff on an annual basis without the Project, it is appropriate 21597/Sconset 2 Response to Third Party Review Epsilon Associates, Inc. to account for that volume of the bluff that eroded and to subtract this volume from the mitigation requirement.” Therefore, we continue to refer to the sand amounts listed in Table 1 in the Sand Delivery and Contribution Report, which shows a surplus of sand. “Additionally, the sand delivery data for the most recent year was not provided.” The Annual Report on which Mr. Berman is commenting was submitted in December 2016, prior to the end of the most recent sand year on March 31, 2017. A new Sand Delivery Report that details sand deliveries and volumes will be submitted later this spring as required. Response to Comments on Section 3.1 “2.1 Sand Delivery – It is important to continue to monitor and report the sand volume delivery activities associated with this project.” We agree; sand deliveries will continue to be monitored and reported on an annual basis as required. 2.2 Bluff Monitoring - Response to Comments “…no information (aka metadata) has been provided on the horizontal/vertical accuracy of the survey, grid cell resolution of the DEM, on-the-ground horizontal/vertical control points, or even the method of topographic survey (i.e., LiDAR vs Photogrammetry).” The survey in April 2016 was a photogrammetry survey. The July 2013 survey, as reported to the Commission at the time of the survey, was a traditional LiDAR survey flown by airplane. For the April 2016 photogrammetry survey: • 105.593 acres were covered in aerial survey • Horizontal/vertical accuracy of the survey o Ground Sample Distance -2.77 cm/pixel o Absolute accuracy: 5.54 cm horizontal, 8.31 cm vertical • 11 Ground control points used (coordinates in meters) o GCP 1 - (419344.026,4570424.093) o GCP 2 - (419519.090,4569638.567) o GCP 3 - (419524.259,4569696.553) o GCP 4 - (419525.654,4569758.021) o GCP 5 - (419511.988,4569825.901) o GCP 6 - (419426.446,4569840.356) 21597/Sconset 3 Response to Third Party Review Epsilon Associates, Inc. o GCP 7 - (419379.226,4570115.801) o GCP 8 - (419438.282,4570138.555) o GCP 9 - (419334.684,4570268.833) o GCP 10 - (419395.732,4570291.118) o GCP 11 - (419283.827,4570427.461) • Root Mean Square Error (“RMSE”) (As a percentage) o X- 0.899748 o Y- 2.862256 o Z- 3.069953 • -Projection of Aerial and DEM - UTM19 o Grid cell resolution of the DEM: 0.0271 x 0.0271 Meters In addition to the aerial topography obtained by UAV in 2013 and 2016, there is also freely available LiDAR data from 2000, 2007, 2010, 2012, and 2014. All of this data can be downloaded with full metadata (i.e. error analysis) from https://coast.noaa.gov/dataviewer . If nothing else these data could be used to quality check the method of using LiDAR for determining volume, as all of these dates overlap with the profiles that were collected for this project and used to determine annual nourishment requirements. The SBPF appreciates the note on additional data available. It is noted that the bluff contribution volume was calculated using long-term data sources from 1994-2013, and so incorporates data sources prior to the LiDAR data from 2000. The bluff contribution rates (as detailed in our memo dated November 1, 2013 that was previously submitted to the Conservation Commission and is included here as Attachment A) were previously checked against and corroborated by both (1) bluff survey data and (2) shoreline change rates. Therefore, some of the quality checks recommended here have already been provided. In fact, the data available for Sconset Beach includes shoreline surveys back to 1994 and represents a much more robust data set than is typically available for coastal projects. Response to Comments on Section 3.1 Monitoring Program Adjustments “2.2 Bluff Monitoring – Depending on the quality of the data, annual aerial bluff monitoring is an efficient method of estimating the volume eroded each year. In addition, I would recommend that a visual survey is performed at least once a month (and right after every storm) in order to determine if any part of the geotube has less than adequate cover (2-3’), or much worse, that it be exposed, and for it to be covered again ASAP.” We agree that aerial bluff monitoring is a useful tool for evaluating the volume eroded from the bluff each year and intend to continue an annual aerial survey. As required by the Project’s Order of Conditions, the geotextile tubes are monitored after every storm (minor 21597/Sconset 4 Response to Third Party Review Epsilon Associates, Inc. or major) and are re-covered as needed, generally in a week or less, depending on safety, weather and other practical considerations. Work logs documenting each time the geotextile tubes are uncovered and subsequently re-covered are submitted quarterly to the Commission. 2.3 Shoreline Monitoring - Response to Comments “The WHG Report utilizes mean low water (MLW) for the vertical datum for their shoreline change report due to previous reporting requirements. The CZM Shoreline Change Project uses mean high water (MHW) shoreline derived from LiDAR or local high water line (HWL) from color orthophotographs as a proxy for MHW. Most shoreline change projects use MHW as that is the vertical datum that will first intersect infrastructure when looking at an eroding shoreline. While MHW and MLW often correlate, they may not be directly tied. For example, after a coastal bank erodes it may cover much of the intertidal zone which would push MLW further seaward, but perhaps not move MHW as far. It might be of use to the Conservation Commission to see how these two datum points on the profiles correlate, and if reasonable WHG may want to switch to using MHW for reporting as this datum is closer to the project array than MLW.” We appreciate the comment and agree there can be certain conventional advantages to using a MHW reference. For instance, CZM recommends the use of MHW as a reference datum for LIDAR and Photogrammetry data because these are remote sensing methods that have difficultly capturing data below MHW even at lower stages of the tide. Even when these data are taken at low tide, wave action can obscure the MLW line making it difficult to detect by either photogrammetry or LIDAR. Therefore, MHW is the better reference datum for those remote sensing technologies. At Siasconset, however, we have the actual survey data that captures data well below MLW. Thus we are not limited by the typical remote sensing based challenges associated with delineating MLW. The selection of MLW also has a historical context at Siasconset. From the first surveys and studies of the beach in 1994, MLW was used as the reference point. We understand one reason is the MLW datum serves as the established vertical datum for the entire project coordinate system dating all the way back to the first survey in 1994. The MLW datum is actually based on tidal benchmarks established in 1992, and is referenced as MLW92. Reference materials are attached (see Attachment B - Explanation of Tidal Datum Used for Siasconset Beach Dewatering Project Per Leo Asadoorian, PLS, Blackwell & Associates, Inc.; March 23, 2004) that document the establishment of the MLW92 vertical project datum. To report the shoreline changes in reference to MHW instead of MLW would cause a disconnect between the recent survey with the prior seventy (70) surveys that have been conducted. While MLW92 was established as a tidal benchmark, we do not have a historic record of MHW locations. There also is the advantage of being able to directly compare current surveys and positions to those surveyed from the beginning. Selection of a datum at 21597/Sconset 5 Response to Third Party Review Epsilon Associates, Inc. this site also is complex, because the tides along Siasconset are different from the established NOAA tidal station in Nantucket Harbor. In fact, local tide measurements we collected showed that high tide elevation varies along the beach. What also is unique to this site is the foreshore slope of the beach profiles is typically very steep along the Siasconset shoreline. There is not a typical equilibrium beach profile with a berm/bar configuration. Rather, the beach foreshore slope tends to be quite steep and linear. When conducting the surveys, the distance between MHW and MLW often comes with a few short paces down the beach slope by the surveyor. Whereas some beaches have different dynamics associated with the location and movement of MHW and MLW, this has not been the case at Siasconset. Shifting the datum from MLW to MHW will not change the shoreline change trends. For all of these reasons, we are comfortable using MLW at this site for technical reasons, and with the added benefit of comparing to a long history of surveys. “Additionally, project shorelines were delineated at the MLW line and not at the toe or top of Bank. While the erosion rates at these locations are certainly linked there is a typically convoluted correlation between them (e.g., 2’ of erosion at MLW does not immediately equal 2’ of loss at the top of the bank). Erosion of the coastal bank can build the adjacent beach, which may indicate accretion when looking at the wet/dry line. The WHG report shows a strong linear relationship between MLW and beach volume. This indicates that MLW might be used as a proxy for beach volume in the future, however MHW should also be graphed in a similar way to determine if the trend is valid for this higher datum as well.” Based on the discussion about MLW and MHW datums above and the steep, linear characteristic of the beach profile, we do not think adding a correlation analysis between MHW and beach volume will produce a meaningfully different result. Since the long-term position of MHW is not readily available from the profiles, there also will be less data to analyze. Thus, we believe the analysis based on MLW is sufficient. “Overall, the major changes in this dynamic area completely overshadow any signal that might be from the geotube project. No additional shoreline change can be attributed to the project at this time.” We agree with this assessment – there is no evidence of increased erosion from the project. Response to Comments on Section 3.1 Monitoring Program Adjustments “2.3 Shoreline Monitoring – The requested reduction to 2 profiles per year is reasonable based on the collected data so far as well as more consistent with MassDEP guidance.” We agree with this assessment. 21597/Sconset 6 Response to Third Party Review Epsilon Associates, Inc. “One of the main reasons to include wading shots in a beach profile (besides to tie into the bathymetry) is to include the potential sand bars, which can hold a significant volume of sediment (especially in winter and post bluff erosion). Without examining individual beach profiles (not included in WHG report) one cannot determine the value of profiling below MLW. While profiling to -5’ MLW can be logistically quite difficult, the request to completely eliminate wading shots might not be necessary. Instead of taking the profile to - 5’MLW the profile could be taken to -2 to -3’MLW, which would be easily accessible on most calm days. While the data shows only an improvement of 1.1cy/ft (1.4%) over extrapolation below MLW, this is based on trying to track 22cy/lf/yr of nourishment (1.1 cy/ft out of 22 cy/lf is 5%). If the volume is changed to 14.3 cy/lf/yr (as requested by the applicant in Section 3.2) this would make the 5% now 8% of the nourishment volume.” We are not certain if any of the monitoring reports were provided to Mr. Berman. We recommend reviewing the latest survey report (see Attachment C), which includes the beach profile plots in an appendix. The beach profile at Siasconset does not follow a typical equilibrium beach profile with a sandbar offshore. Due to the dynamic and erosive nature of the wave climate at Siasconset, the beach has a very steep foreshore slope offshore typically to about -7 to -10 feet MLW before becoming more gradual, particularly in the Project area. The beach profile also typically lacks a definitive sandbar even during different seasons. And, given the nature of the profile, there would not be a sand bar supported on the steep beach face at these relatively shallow locations. Changing the depth of the wading shots from -2 to -3 feet MLW instead of -5 ft-MLW also does not, unfortunately, change the data collection method as the total station and survey rod would still be needed since the profile drops off steeply. After reviewing the RTK GPS data, the topo survey can only wade down to 0-ft MLW before there is a steep slope break. Thus, the wading shots do not record potential sand bars and associated volumes. Therefore, we continue to recommend that extrapolation from 0 MLW to -5 feet MLW would result in important survey efficiencies and decrease risk to the survey crew without a degradation in the quality of the data. Additionally, the mitigation volume of 22 cy/lf/yr is a based on the amount of material contributed by the bluff annually to the beach, 14.3 cy/lf/yr, along with a conservative safety factor of nearly 8 cy/lf/yr. This difference in the calculated beach volume of 1.1 cy/ft between extrapolation method and the surveyed profile data only exists on the submerged portion of the profile between 0-ft MLW and -5ft-MLW, where only 6% of the beach profile volume is contained. Assuming that there would be 8% error (1.1 cy/ft / 14.3 cy/lf/yr) in tracking the mitigation volumes assumes that the entirety of the 14 cy/lf/yr of material is located between 0 and -5 ft-MLW all at one time, when in fact this material is likely spread over different portions of the beach at any given time. Furthermore, spreading this beach volume difference of 1.1 cy/ft over this distance between 0-MLW and -5-MLW, typically 60 to 100-ft, equates to a vertical difference of about a 1/10th of a foot over this distance, which is well within the survey error for the wading shots. 21597/Sconset 7 Response to Third Party Review Epsilon Associates, Inc. 2.4 Wetland Well Monitoring - Response to Comments “It is highly likely that the catch basin (on the east side of the road) has no effect on wetland water levels on the west side of the road…” We agree with this assessment. “There is also a reference to “50 previous well readings…from 2001-2007” helping define the expected variation (2-5’ over 6 years), however no mention of what wells or the sampling parameters/timing are explained. Additionally, it is not only the range that is important for wetlands. If the annual low gets lower than historic levels then there may not be as much water as there used to be during dry times. It’s unlikely this has changed significantly, but it cannot be determined from the information provided.” As noted in the report, over 50 well monitoring events occurred in the period of 2001- 2007, which is 10-15 years before the most recent data collected in 2016 and included in the Annual Report. These past readings were previously provided to the Commission and are attached here for ease of reference (see Attachment D). These historic readings can provide a general context for the 2016 readings, but the significant time period (9-15 years) between the datasets provides limitations on the conclusions that can be drawn. • There are six wells (E-1 through E-6, referred to as the “historic wells”) monitored in the period from 2001-2007 that are located on the seaward side of lots 84-96 Baxter Road (i.e., the same area as current wells E-2, E-4, and E-6R). (Note: new wells E-2 and E-4 are in slightly different locations than historic wells E-2 and E-4). • In five of these six historic wells, the previous historic low water levels ranged from 7.1 to 8.3 feet below the surface, with the 6th historic well (E-4) having notably higher groundwater with a lowest reading of 4.2 feet. • The historic well readings were taken from the ground surface whereas the 2016 well readings, as indicated in the Annual Report, were recorded from the top of the well, which is about 8-inches above the ground surface. To allow a direct comparison, the 2016 low readings (9.2-10.8) are adjusted by 8 inches to record a depth from the ground surface of approximately 8.5-10 feet. • The historic well low readings (7-8 feet) are in the same ballpark as the 2016 adjusted low readings (8.5-10 feet), though the 2016 readings are somewhat lower. No further conclusions can be drawn from the data given the 9-15 year period between well readings. We reiterate both our comment and Mr. Berman’s comment that it is unlikely that the catch basin would have impacted the wetland water levels. We note that 21597/Sconset 8 Response to Third Party Review Epsilon Associates, Inc. water levels in the wells appear to correlate well with precipitation and that a visual assessment of the wetland suggests it is not being impacted by the Project. Response to Comments on Section 3.1 Monitoring Program Adjustments “2.4 Wetland Well Monitoring – If the data from 2001-2007 shows similar dry levels as this project the well monitoring could be discontinued.” The historic well data from 2001-2007 shows generally similar dry levels as the 2016 data. Additionally, the well data from 2016 appears to correlate well with precipitation, and the range of water levels observed is similar in the 2016 data as in the historic data from 2001- 2007. These findings support the recommendation that the monitoring be discontinued. 2.5 Beach Invertebrate Monitoring - Response to Comments “The low abundance of invertebrates in the area likely do not warrant further sampling….2.5 Beach Invertebrate Monitoring – The invertebrate monitoring could be discontinued as no impacts to the few species have been observed.” We agree with this assessment. 2.6 Underwater Video Monitoring - Response to Comments “The survey dates of 2007 and 2016 are too far apart for a coherent analysis in such a dynamic area… Additionally, the geotubes were installed in 2013/2014 and so seven years have passed between the “baseline” study and the installation.” We agree with this statement and stated similar reservations or caveats in our report. We attempted to make a comparison since the 2007 data represented the most recent video data available, but we are in agreement that the significant time passing between events limits the ability to make a definitive comparison. Nonetheless, we believe the data show that a productive cobble habitat was present offshore of Sconset in both 2007 and in 2016 and that there is no evidence that this cobble habitat is being covered, nor is there an expectation that this would occur based on the volume of mitigation material. “2.6 Underwater Video Monitoring – Video monitoring likely is not needed yearly. Sidescan sonar or backscatter might be more efficient at classifying bottom type than underwater video, although it would miss the species of flora and fauna provided by video. Sidescan would give seamless bottom coverage, but would need a few ground truth points (video/planview/SPI). Even a high-resolution (aka chirp) seismic profiling system would be unlikely to distinguish any fine layering of nourishment sand on the near coastal system. Another method that has been used to determine sediment coverage and depth is Sediment Profile Imagery (SPI). This technology uses a camera housing and penetrates the sediment/water interface. The resulting image shows the shallow stratigraphy below the 21597/Sconset 9 Response to Third Party Review Epsilon Associates, Inc. interface, and might be of use in this project if the nourishment sand can be distinguished from native sand. In areas of high cobble this system doesn’t work well.” We agree with this assessment that video monitoring is not needed yearly and suggest it only occur once every three years or in the event that the mitigation template contributes 3- 5 times more sand than the unprotected bluff. We agree with the statement that the SPI camera doesn’t work well in areas of high cobble like Sconset and do not believe this tool would be a good fit for the Sconset project, due to both the high presence of cobble and other hardbottom and due to the difficulty of distinguishing the nourishment sand from native sand. SBPF will evaluate if sidescan sonar is a potential means of completing the survey. As noted by Mr. Berman, sidescan will not provide information on flora and fauna but will provide information on bottom coverage type (sand vs. cobble). 2.7 Annual Drainage System Report - Response to Comments “If the accumulated sediment is below the threshold for cleaning (as indicated in the Epsilon Report) then the system is likely performing as designed…If the town is willing to take this monitoring program over after one more year it would likely be minimal effort.” We agree with this assessment. 3.2 Mitigation System Adjustments - Response to Comments “Standard compensatory nourishment can be calculated by multiplying the erosion rate, by the existing landform height and length to get a volume…” We agree that standard compensatory nourishment can be calculated by multiplying the erosion rate by the landform height and length. However, as described below, we took a more conservative approach when calculating the Sconset nourishment volume. Standard Compensatory Nourishment Volume Below is how the standard compensatory nourishment would be calculated by multiplying bank erosion rate * length of landform * height of landform: First we calculate the bank height in the Project area: 21597/Sconset 10 Response to Third Party Review Epsilon Associates, Inc. Bank Height 87-105 Baxter Road Location Top of Bank (ft MLW) Toe of Bank (ft MLW) Bank Height above Toe (ft) 105 Baxter 93 10 83 101 Baxter 85 10 75 99 Baxter 80 10 70 97 Baxter 78 10 68 93 Baxter 78 10 68 91 Baxter 74 10 64 87 Baxter 77 10 67 Average height (ft) 71 Next we calculate the nourishment volume using the standard methodology: Standard Calculation of Compensatory Mitigation Bank Retreat (ft/yr) Length of Landform (ft) Bank Height (ft) Mitigation Volume 4.6 947 71 308046 cf 11409 cy 12.0 cy/lf This standard calculation results in a mitigation volume of 12.0 cy/lf/yr. Sconset Calculation of Nourishment Volume As discussed in detail in the November 1, 2013 memo provided to the Commission during its review of the NOI (and included here as Attachment A), a more conservative approach was taken for Sconset. We felt that taking a vertical slice of the bluff (by multiplying the retreat rate by the landform height) may not fully account for how much the material the bluff contributes since it has a tall, sloping face. We therefore applied the retreat rate to actual cross-sections of each of the lots and calculated the volume contributed from each profile of the bluff. This more conservative approach yielded 14.3 cy/lf/yr, which is nearly 20% higher (19% higher) than the standard calculation. Therefore, there is already some conservatism incorporated into the calculation. “The Epsilon report requests that, at a minimum, the average volume (14,000 cy) be placed as mitigation without the extra 50% safety factor. Instead the safety factor would be the requirement to keep the geotube covered with sand at all times. If the Conservation Commission approves this adjustment they may want to consider that ANY exposed section of geotube would require sand placement such that the geotube is then covered by at least 21597/Sconset 11 Response to Third Party Review Epsilon Associates, Inc. 2-3’ of sand again, within a very short time period. The Conservation Commission could also reduce the safety factor over time to see if there are negative effects occurring (ie. Dropping the safety factor by 10% each year, so from 50% it would be 0% in 5 years). If it is the intention of the applicant to attempt to hold the shoreline in its current position, the nourishment required would be needed in perpetuity at an increasing level of cost and effort as sea level rises and the rest of the shoreline changes.” We continue to identify the need for a more adaptive mitigation program. We suggest that a minimum volume of 14.3 cy/lf/yr be placed each year, with an ongoing requirement to keep the geotextile tubes covered. In a more energetic year, more sand would be needed to keep the geotextile tubes covered than the required 14.3 cy/lf/yr. As noted above, this 14.3 cy/lf/yr is more conservatively calculated than at any other known project in Massachusetts. Additionally, the Project has been installed for four winters, so we believe now is an appropriate time to consider a more adaptive mitigation program. As an additional idea of an adaptive mitigation program, DEP suggested a process whereby the required volume of 22 cy/lf/yr is available on the sand template at the start of each sand year (April 1) and that new sand is delivered to “re-fill” the template to that level at the end of each sand year (March 31), such that however much sand is eroded during storms is replaced each year. In the event more than 22 cy/lf/yr erodes in an energetic year, additional sand would be provided on an as-needed basis throughout the winter to keep the geotextile tubes covered with sand. Such an adaptive approach allows the mitigation sand to more closely match the natural system in which the amount that actually erodes varies from year to year. SBPF has always acknowledged that mitigation sand will be needed in perpetuity and accepts this requirement. Additional Considerations – Response to Comments “The project site has not experienced a significant storm event since the installation of the geotube array. Until data is available from the geotube array experiencing a larger storm (for example with Stillwater elevations intersecting the geotube array), the Conservation Commission may want to carefully deliberate before removing conservative controls on the project (ex. high volume of nourishment and monitoring).” We are not certain which criteria are being used to state that the Project has not experienced a significant storm. The Project has experienced the following large, named storms during the nearly 3.5 years since its construction. The storm marked with an asterisk meets the 21597/Sconset 12 Response to Third Party Review Epsilon Associates, Inc. Commission’s definition of a significant1 storm (sustained windspeeds of 40 mph for 6 hours or more): Date of Storm Major Storms January 26-27, 2015 Juno* January 23-24, 2016 Jonas February 8-9, 2016 Mars September 5, 2016 Tropical Storm Hermine * Meets definition of "significant" storm As the geotextile tubes have been in place for four winters, we believe it is an appropriate time to consider a more adaptive sand mitigation program. Due to the scale of this project (947’ length) there is a high potential for current to set up parallel to the smooth exposed geotube during storm conditions with oblique waves. This type of current can rapidly scour the end of the array, even with a well-built return. While we acknowledged during the NOI review process that end scour can occur, there is no evidence of this occurring. The geotextile tubes are checked after every storm and we have not observed signs of end scour. The visual inspections suggest that the returns and the large volume of mitigation sand covering them are functioning as designed to prevent flanking from occurring. “One of the dangers of “holding the line” with either a CES or softer alternatives (i.e. coir envelopes/fencing) is that the stabilization array will eventually, artificially protrude further seaward than the rest of the shoreline. Flanking may occur if adjacent properties continue to erode naturally, while the project site maintains a shoreline position further seaward than necessary to protect the house. Flanking could require returns to be extended landward over time in order to protect the house, which would allow the property to protrude further 1 We do not believe the reference to a “larger storm” being defined by stillwater elevations reaching the base of the geotubes is accurate. The elevation near the toe of the geotextile tubes is typically ~10 feet MLW. Based on the 2014 FEMA FIS, the 100-year FEMA floodwater elevation for the area near the Sconset geotube project (Transect 13) is 5.8 feet NAVD88. This elevation is converted to the project datum of MLW using a conversion of 1.52 feet, resulting in a 100 year stillwater elevation of 7.32 feet (MLW). Thus, the 100-year flood stillwater elevation (7.32 feet MLW) is well below the toe of the geotextile tubes (~10 feet MLW). We do not think it was the intent of this comment to require something greater than a 100-year storm to meet the definition of a “larger storm.” 21597/Sconset 13 Response to Third Party Review Epsilon Associates, Inc. seaward than the rest of the shoreline and affect the coastal processes (erosion and sediment transport)…. “Erosion doesn't stop in areas adjacent to a shoreline stabilization project and "holding the line" can become more and more difficult over time. Eventually there will be a time when the landward retreat of the array, to be more compatible with the surrounding shoreline, will be the preferred course of action….A section in the Work Protocol on the eventual retreat (or abandonment) of the array might be helpful and inform monitoring activities to support the long-term longevity of stabilization methods being utilized at this site.” Many of these general comments were discussed extensively during the NOI review process. While we provide brief responses to these general comments below, we note that the purpose of the annual review, as listed in the Project’s Order of Conditions, is to review monitoring data and “recommend any necessary changes to the beach nourishment program for the Conservation Commission's review and approval,” for the existing, approved geotextile tube project. Regarding the comments about flanking, Project representatives acknowledged during the public hearing process on the NOI that returns may have to be lengthened over time. Additionally, the SBPF intends to pursue permits for an expanded system in the future. Such an expansion would result in a long, contiguous portion of the bluff that is protected (approximately 3,400 linear feet). This type of project where nearly 2/3 of a mile of bluff will be protected is different than the typical segmented project where only one or two lots are protected and where flanking is a significant consideration, especially if such shorter projects do not have sand mitigation or well-designed returns. For this longer project with its substantial sand mitigation program, it is anticipated that the protected section of bluff and associated beach, while it may eventually protrude farther seaward than the immediately adjacent shorelines, will continue to have a beach in front of it and will continue to allow littoral processes to continue. As was discussed during the NOI review process, we expect a similar response from the geotextile tubes as we have seen with >10 years of bluff protection via the biodegradable terraces at 79 Baxter Road and other locations, where there is some shoreward protrusion of the bluff yet there is still a dry beach present in front of the terraces. While we anticipate that the sand mitigation program will assist in maintaining a beach in front of the geotextile tubes, if there is some future effect on sediment transport processes, the placement of the mitigation sand could be adjusted to provide a higher proportion of sand at the ends of the geotextile tubes than in the front of the geotextile tubes. We disagree with the statement that the eventual retreat or abandonment of the Project will be required. With a commitment to ongoing sand mitigation, the homeowners of the SBPF are dedicated to long-term preservation of the bluff and this historic neighborhood. 21597/Sconset 1 Response to NLC/ACRE Comments Epsilon Associates, Inc. RESPONSE TO COMMENTS FROM THE NANTUCKET LAND COUNCIL/ APPLIED COASTAL RESEARCH AND ENGINEERING This document presents responses to the three main comments provided by Applied Coastal in a memo dated April 12, 2017. Comments excerpted from the memo are presented in italicized text followed by responses in plain text. “A great deal of emphasis has been placed on the variability of the measurements contained in the beach monitoring datasets and how the variability limits the value of data as a useful tool to evaluate the performance of the geotube project….At the six profiles examined by Epsilon, the erosion rate post geotube construction is higher than the historical long-term erosion rate.” We agree with the ACRE statement regarding differences between short- and long-term changes. This is exactly why we’ve introduced the long-term data into the annual and quarterly reports. We also explored various statistical comparisons and trends, and concluded there is not yet a statistically defensible result. As ACRE stated in their analysis, short-term data can be inconclusive when viewed over long periods. Thus, it is not yet meaningful to compare the relatively short-term beach responses since the geotubes were installed against the long-term record. In fact, what we found is similar short-term shoreline changes previously occurred several times over the long-term record. This is apparent visually from the plots in the ACRE memo. We also recognized the period of beach accretion preceding the geotube installation, which as ACRE stated was anticipated to be followed by a period of erosion independent of the geotubes. These natural dynamics, combined with movement of the added sand volume placed in the project area for mitigation, may also skew or mask the response of the beach subsequent to the geotube installation. We plan to continue using regular comparisons against the long-term data record to help ascertain potential project influences, appropriate mitigation, and overall project management. “The bluff monitoring program was utilized to compute the volume of material contributed from the unprotected bluff to the littoral system….It is to be expected that the areas to the north and south of the project area would contribute lower volumes of sediment as they are located outside the initial project area.” We agree that it is worthwhile to compare the volume of material eroded from the geotextile tube area to the unprotected areas to the north and south that were used as “control” areas during the bluff monitoring survey. As shown on the attached (see Attachment E), we reviewed the bluff erosion rate for the geotextile tube area, the north control area, and the south control area. The time period reviewed was from 1994-2013 for those areas that had begun eroding in 1994 (91 Baxter northward) and 2003-2013 for those areas that began eroding later (91 Baxter southward). We first looked at bluff retreat rates 21597/Sconset 2 Response to NLC/ACRE Comments Epsilon Associates, Inc. for the geotube area and the control areas using the same methodology used to determine the bluff contribution rate in the geotube area (see Attachment E), and then we performed a simple volume calculation using bluff retreat rate * height. As noted in the response to Mr. Berman, we do not recommend using this simple calculation for determining the bank contribution rate for mitigation purposes, but it is useful here for comparing relative volume contribution from different bluff segments. This comparison indicates that the volume eroded from the north and south control areas is about 80% of the volume eroded from the geotextile tube area. We note that there is significant temporal and spatial variability in the amount of bluff erosion, with erosion hotspots developing in one location for a few years and then moving on to another location. Thus, the relationship between the volume eroded from the unprotected control areas and the volume eroded from the geotube area will vary through time. However, the availability of 25+ years of data on erosion volumes provides a high degree of assurance that mitigation volumes can be compared to historic rates or erosion over time. Nevertheless, we will add a note to all future comparisons of control area erosion to geotube area erosion that the control areas may slightly underestimate the volume of sand that would have eroded from the geotextile tube area. However, this does not change our overall conclusion that the mitigation template is contributing more sand than the unprotected bluff: if we adjust the measured control area erosion of 12.9 cy/lf/yr upwards to account for the 80% proportion, we get ~16 cy/lf/yr, which is still less than the mitigation template contribution of 18.1 cy/lf/yr. Overall, the current bluff contribution amount is just one of several tools we use when evaluating the geotextile tube project: we also compare the mitigation volume to the historic bluff contribution rate, we review the post-geotube shoreline change data compared to the long-term trend, and we monitor the geotubes after every storm. When all the data are considered together, we do not see any evidence of increased erosion of adjacent beaches. “SBPF claims that the mitigation volume required for the geotube project is 1.5 times the average annual bluff contribution rate, which is not supported by the data or their analysis. The required mitigation rate of 22 cy/lf/yr was arrived at through scientific and engineering studies and analysis conducted by SBPF consultants on previous Sconset Beach projects.” A detailed response to this comment has been provided on numerous occasions over the past nearly four years during other Conservation Commission hearings, most recently during the NOI hearing process for the geotube project. We are attaching our November 1, 2013 memo (Attachment A), which addressed this comment in detail and provided the means used to calculate the bluff mitigation volume. The below table from the November 2013 memo includes previous mitigation volume calculations for other projects proposed by SBPF and describes that the 14.3 cy/lf/yr is the most conservative calculation of bluff contribution volume performed to date. We also note that the source of confusion appears to be that the marine mattress and gabion pilot project included a nearshore component of 21597/Sconset 3 Response to NLC/ACRE Comments Epsilon Associates, Inc. ~7 cy/lf that represents the volume of sand out to the depth of closure at -26 feet MLW (about 1500 feet offshore). This nearshore component is not included in the bluff contribution calculations for the geotextile tube project since, as noted both in the Epsilon memo and in the third party review by Mr. Berman, the state standard for mitigation is to provide the average amount contributed from the eroding landform (the bluff). The attached Epsilon memo (Attachment A) also explains how the calculation used to determine the bluff contribution volume was corroborated by both (1) bluff survey data and (2) shoreline change data. The attached memo provides ample support for the mitigation calculation. Table I. Summary of Sand Mitigation Volumes in SBPF Proposals Project Project Area Years Used in Calculation Retreat Rate (ft/yr) Volume (cy/lf) Geotube (Current Town Application) 85-107A Baxter 1994-2013 (91-107A Baxter) 2003-2013 (85-91 Baxter) 4.6 14.3 Revetment 63-119 Baxter 1994-2013 (91-119 Baxter) 2003-2013 (71-91 Baxter) 3.8 12.0 Gabion 77-85 Baxter (North) 63-67 Baxter (South) 2003-2010 (North) 2001-2011 (South) 4.96 (North) 3.62 (South) North 11.6* (Bank) 6.8 (Nearshore) 20** TOTAL South 7.5* (Bank) 7.2 (Nearshore) 16** TOTAL *Excludes 13% fines **Includes overfill allowance “We agree with Epsilon that the aerial bluff monitoring should continue on an annual basis. The program could be expanded to monitor changes in the aerial beach profile, which could provide important information regarding the position of the geotube toe relative to the highwater line. At the conclusion of the 3-Year Special Conditions window required as part of the permit for the geotube project, the shoreline monitoring could be shifted from a quarterly basis to spring and fall surveys without jeopardizing the dataset. However, we disagree that the profile surveys should be truncated at the waterline and not include the nearshore bathymetry. The shape of the aerial and subaerial beach profile is important for understanding and monitoring the dynamics of the littoral system.” 21597/Sconset 4 Response to NLC/ACRE Comments Epsilon Associates, Inc. We will continue the annual bluff monitoring and believe that now is an appropriate time to switch to semi-annual beach surveys, a position also supported by Mr. Berman. We also believe our analysis of extrapolation and the associated small errors (1.4%) demonstrate that extrapolation is a reasonable technique that can drastically improve survey efficiency and reduce risks to the survey crew. “Reducing the number of survey profiles was discussed. Prior to any reduction in the number of profiles, it is important to understand which profiles would be eliminated. It is important to ensure that long-term monitoring stations are not eliminated, nor monitoring stations that will provide the first evidence of potential adverse impacts associated with the geotube project, as well as future projects which SBPF are preparing.” As clarification, our suggestion for reducing the number of survey profiles was only for the bathymetry surveys, so that the survey can be completed within one day. We suggested we retain all historic whole number profiles plus Q, S and W. As noted in the analysis by Woods Hole Group attached to the Annual Report, the bathymetry offshore Siasconset features a generally stable profile, particularly in the northern and central portions of the monitoring area (which includes the geotextile tubes). Bathymetry data are helpful for general scientific purposes to understand regional coastal processes (e.g., offshore shoal movements and evolutions), but are not conclusive for determining whether the geotextile tubes are having an adverse impact upon adjacent beaches. Shoreline position data are most useful for that purpose. Bathymetry surveys conducted a maximum of once per year are sufficient to characterize regional morphology. Attachment A November 1, 2013 Epsilon Memo “Baxter Road Geotube Project – Coastal Bank Retreat Calculations” Page 1 M E M O R A N D U M Date: November 1, 2013 To: Kara Buzanoski, Nantucket DPW From: Maria Hartnett, Epsilon Associates Subject: Baxter Road Geotube Project – Coastal Bank Retreat Calculations The following memo summarizes information about the ‘Sconset bluff volume contribution calculation, including (1) a comparison of the current proposed sand mitigation volume with past Sconset Beach Preservation Fund (SBPF) proposals; (2) details on how the bank retreat rate and associated volume were calculated, including data tables; (3) comparison of the calculated bank retreat rates with shoreline change rates; (4) comparison of the calculated bank contribution volume with bank survey data; (5) a discussion of CZM’s sand volume mitigation recommendations for the Project area; and (6) a discussion of Coastal Planning & Engineering’s littoral budget prepared for the previously-proposed beach nourishment project. The Town of Nantucket requested that I prepare this memo due to my long history of calculating the bank retreat rates and associated volumes. 1.0 Comparison with Bank Retreat Rates and Volumes in Previous Submittals The following table (Table 1) summarizes the bank retreat rates and volumes provided by SBPF during project filings for the marine mattress and gabion projects, the revetment, and the geotube project. There is significant spatial and temporal variation in coastal bank retreat rates along the ‘Sconset bluff. Retreat rates are calculated along multiple transects for each lot; therefore, different project areas will have different retreat rates and associated volumes. The table below shows that each of the SBPF filings has involved a different project area. Variations in the sand mitigation volume proposed by SBPF are also a result of the varying nature of bluff erosion over time. Erosion of the bluff is an ongoing process and SBPF has periodically undertaken additional LIDAR surveys of the project site; therefore, more recent data (2013 LIDAR survey) were available for use for the geotube and revetment project than for the gabion project (2010 LIDAR survey). Similarly, the geotube and revetment project areas include project areas farther to the north, where bank retreat was occurring as far back as 1994, and therefore a more long-term bank retreat rate could be determined for the geotube and revetment projects (bank retreat rates from 1994-2013 and 2003-2013 could Page 2 be determined for the geotube and revetment projects vs. a 2003-2010 bank retreat rate for the gabion project). For the geotube project, the Town intends to follow the state standard of “Best Available Measure,” which has been consistently required by DEP, CZM, and many local Conservation Commissions. The state standard of “Best Available Measure1” for sand mitigation is to provide to the littoral system, on an annual basis, the average amount of sand that would have been provided by the eroding bank absent the project. For the marine mattress and gabion project, SBPF offered an additional component of sand mitigation (~7 cy/lf to replicate the amount of sand eroded from the nearshore); this extra component was only associated with that pilot project (which was never implemented) and is not relevant for the current project. Table I. Summary of Sand Mitigation Volumes in SBPF Proposals Project Project Area Years Used in Calculation Retreat Rate (ft/yr) Volume (cy/lf) Geotube (Current Town Application) 85-107A Baxter 1994-2013 (91-107A Baxter) 2003-2013 (85-91 Baxter) 4.6 14.3 Revetment 63-119 Baxter 1994-2013 (91-119 Baxter) 2003-2013 (71-91 Baxter) 3.8 12.0 Gabion 77-85 Baxter (North) 63-67 Baxter (South) 2003-2010 (North) 2001-2011 (South) 4.96 (North) 3.62 (South) North 11.6* (Bank) 6.8 (Nearshore) 20** TOTAL South 7.5* (Bank) 7.2 (Nearshore) 16** TOTAL *Excludes 13% fines **Includes overfill allowance 2.0 Description of Methodology The coastal bank retreat calculation was developed using the 2013 LIDAR data and high- resolution georeferenced aerial photographs dating back to 1994 to establish a long-term bank retreat average. 1 Best Available Measure(s) is defined in 310 CMR 10.04 as “… the most up‐to‐date technology or the best  designs, measures or engineering practices that have been developed and that are commercially  available.  Page 3  Bank Retreat Rate. The top of the coastal bank was digitized for 1994, 2003, and 2013 using ESRI ArcGIS software to produce the attached figure (see Figure 1). Top of coastal bank retreat was analyzed along shore-perpendicular transects spaced approximately every 20 feet. o For the portions of the geotube project area from 91-107A Baxter Road, the top of coastal bank was actively retreating as early as 1994. For these lots, a long-term (1994-2013) coastal bank retreat rate of 4.0 feet/yr was calculated. This was calculated by taking the average of the coastal bank retreat along each transect within the area from 91-107A Baxter Road (see Table 1). o For the portions of the project area from 85-91 Baxter Road, the top of coastal bank was not actively retreating in 1994 (Figure 1 shows that the 1994 and 2003 top of bank lines are coincident south of the southern half of 91 Baxter Road). For these lots, a 10-year (2003-2013) bank retreat rate of 5.8 feet/yr was calculated. This was calculated by taking the average of the coastal bank retreat along each transect within the area from 85-91 Baxter Road (see Table 1). o For the entire Project area, a single average coastal bank retreat rate was calculated by averaging the above two rates. The average is distance- weighted by transect, which reflects the fact that the majority of the geotube project area has a long-term erosion rate of 4.0 feet/yr, with only the southern 30% exhibiting the higher erosion rate of 5.8 feet/yr. The distance- weighted average is 4.6 ft/yr (see Table 2).  Volume Calculation: Section views from each of the Project lots from 85-107A Baxter Road were developed from the 2013 LIDAR survey. The volume associated with a bank retreat of 4.6 ft/yr was then determined for each lot using AutoCAD (see typical Figure 2, which shows how the cross-sectional area and associated volume were calculated for each lot). A distance-weighted average volume for all the project lots was then determined (see Table 3), yielding 14.3 cubic yards/linear foot/year (cy/lf/yr). 3.0 Corroboration of Methodology by Survey Data The bank retreat volume contribution methodology, based on LIDAR data and aerial photography, was corroborated by independent calculations performed by Woods Hole Group (WHG). WHG has top and toe of bank survey data available at profiles 90 (near 69/71 Baxter Road), 90.5 (near 79/81 Baxter Road), and 91 (near 91 Baxter Road), in years 2006, 2008, and 2013. While these data are too limited to use for the geotube project area since they do not extend far enough northward, they provide a useful check of the above methodology. WHG utilized the top and toe of bluff survey data to calculate a bank contribution volume of 12.4 cy/lf for the area covered by the profiles (69/71 Baxter Road – Page 4 91 Baxter Road); see Tables 4a and 4b. When the above methodology as described in Section 2 was applied to the same project area (71-91 Baxter Road, for years 2003-2013), the volume calculated was 13.2 cy/lf. The high degree of similarity between these two numbers (they are within 10% of one another) suggests that the methodology used by Epsilon provides an accurate representation of the bank contribution volume, and may even slightly over-estimate the bank contribution volume. 4.0 Corroboration of Methodology by Shoreline Change Data This calculation was also corroborated by shoreline change data. The WHG shoreline change data for the area from 91-107A Baxter Road were compared to the calculated bank retreat rate for 91-107A Baxter Road. The complete March 2013 WHG Shoreline Monitoring Report is included as Attachment A.  Epsilon Methodology: the 1994-2013 bank retreat rate from 91-107A Baxter Road was calculated as 4.0 ft/yr.  Shoreline Data: the 1994-2013 distance-weighted shoreline change rate for those profiles located nearest to 91-107A Baxter Road (profiles 91, 91.5, and 92) is 3.9 ft/yr. (See Table 5.) The high similarity between these two numbers again supports the accuracy of the calculated bank retreat rate, and suggests that the above methodology may also be slightly conservative. Comparisons between 1994-2013 shoreline change rates and bank retreat rates were not made for areas farther south of 91 Baxter Road, since the coastal bank was not actively retreating throughout this time period. 5.0 Discussion of CZM Recommendations Ms. Rebecca Haney of CZM provided a recommended sand volume to the Conservation Commission in a letter dated August 26, 2013 for the revetment project. As noted in SBPF’s submission to the Conservation Commission on September 6, 2013, Ms. Haney’s suggestion to utilize short-term shoreline change rates from 1978-2009 to estimate the volume of sediment eroded from the coastal bank fails to consider the coastal setting at Sconset and, by doing so, recommends the use of irrelevant data. The Sconset shoreline and beyond (from the Sewer Beds at the south to Wauwinet at the north) have been carefully monitored on a quarterly or semi-annual basis for nearly twenty years, yielding an impressive record of highly-accurate data. This monitoring has consistently shown that shoreline erosion rates in areas where the coastal bank is fronted by dunes are significantly higher than shoreline rates in areas with an eroding coastal bank. (This observation is as expected, since an eroding dune contributes less to the littoral system than an eroding bank.) In other words, survey data show that the shoreline change rates in areas fronted by Page 5 dunes are not representative of the coastal bank retreat rate. Rather, the shoreline change rate and coastal bank retreat rate may only begin to approximate one another after the coastal dune and any vegetated portion of the coastal bank have completely eroded and sufficient time has passed for an equilibrium to be reached. The coastal dune in the Project area was still present during much of the 1978-2009 time period; therefore, Ms. Haney’s suggestion to use a 1978-2009 shoreline change rate to approximate coastal bank retreat is untenable. Ms. Haney quotes a shoreline change rate of 6 to 10 feet/yr from 1978-2009 in the "project area," but this analysis apparently overlooks the northern section of the revetment project area. The CZM shoreline change data for the Project area (63-119 Baxter Road; CZM transects 285 through 306) indicates somewhat lower shoreline change rates, in the range of 4 to 9.7 feet/yr, and even these rates are in applicable given that they reflect dune erosion, not bank erosion, in the earlier years. Additionally, the CZM data is subject to uncertainty; such uncertainty is inherent to the methodology of identifying a shoreline from aerial photographs used for the broad-reaching CZM shoreline change data project. Although CZM quantifies this uncertainty for each transect; Ms. Haney fails to acknowledge this uncertainty, even though the average uncertainty for the transects in the Project area is almost 3 feet. Ultimately, Ms. Haney’s analysis does not consider the coastal setting at Sconset and therefore in our opinion does not provide an accurate representation for this project. 6.0 Discussion of the 2005 CP&E Sediment Budget During the permitting effort for the beach nourishment project, Coastal Planning & Engineering (CP&E) prepared a littoral budget based upon data from 1995-2005. (See FEIR, Sconset Beach Nourishment Project, November 30. 2006. Attachment A, Coastal Planning and Engineering (CPE) Engineering Design Report, Sconset Beach Nourishment Project, Nantucket, Massachusetts. Section 8.0, “Littoral Budget” is included as Attachment B to this memo.) This sediment budget relied upon several assumptions (such as locating the nodal point at the area of greatest erosion, applying the shoreline change rate to entire coastal profile [including eroding coastal bank], determining the volume associated with each profile by multiplying the active profile height times the shoreline recession rate and effective distance between profiles) that are appropriate for use in designing a beach nourishment project, but that may not be as appropriate for quantifying the volume and direction of sediment transport in the project area for the purposes of designing a sand mitigation program. While we feel that the CP&E analysis for the beach nourishment project has limitations when applied to the geotube or revetment project, we nonetheless reviewed their analysis to serve as another check of the proposed sediment mitigation volume. Table 6 presents the CP&E sediment budget values for those profiles within the geotube Project area (profiles 91, 92, and 92.5). The table has been updated from the original CP&E Page 6 analysis in three places: (1) the shoreline change rates have been updated to reflect the most current conditions, based on the results of the March 2013 shoreline survey; (2) the active profile height has been changed to reflect the height of the eroding bank, rather than the entire coastal profile out to the depth of closure, to reflect the geotube project’s commitment to mitigate the amount of sand eroded from the coastal bank; (3) the discount of the silt percentage applied by CP&E has been removed. This analysis yields an estimated bank contribution volume of 11.4 cy/lf (see Table 6). This volume is lower than the proposed volume of 14.3 cy/lf, again indicating that the sand mitigation volume proposed for the geotube project is adequate and possibly conservative (i.e., it may slightly overestimate the bank contribution volume). BAXTER ROAD SAN K A T Y R O A D 85 99 97 87 101 83 105 109 93 91 107 81 107A 113 Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community G:\Projects\Lighthouse\2013\ConCom\Retreat\Revised\Detailed_Analysis_v2\1994-2003-2013.mxd Baxter Road Nantucket, MA Figure 1 1994-2013 Average Retreat for Lots 91-107A = . Feet/Year 2003-2013 Average Retreat for Lots 85-91 = 5. Feet/Year Overall Average Retreat for Lots 85-107A = 4.6 Feet/Year Average Coastal Bank Retreat Summary Coastal Bank Retreat LEGEND Basemap: 2013 Aerial Imagery, Col-East, Inc. 1994 Top of Coastal Bank 2003 Top of Coastal Bank 2013 Top of Coastal Bank Parcel Boundary °0 60 12030 Feet1 inch = 120 feet Scale 1:1,440 Figure 2 Coastal Bank Sediment Contribution – Representative Profile (85 Baxter Road) Baxter Road Nantucket, Massachusetts Retreat = 4.6 ft/yr Average = 14.3 cy/lf Table 2. Top of Coastal Bank Retreat Rate Data for 85-107A Baxter Road (1994-2013) Retreat (ft) Rate (ft/yr) Retreat (ft) Rate (ft/yr) 30 107A 46.2 2.4 31 107A 43.9 2.3 32 107A 47.5 2.5 33 107 51.1 2.7 34 107 56.2 3.0 35 107 53.8 2.8 36 107 57.7 3.0 37 107 57.3 3.0 38 105 50.2 2.6 39 105 50.0 2.6 40 105 58.5 3.1 41 105 82.3 4.3 42 105 84.0 4.4 43 105 79.8 4.2 44 105 77.4 4.1 45 105 75.9 4.0 46 105 74.7 3.9 47 101 79.4 4.2 48 101 76.8 4.0 49 101 77.3 4.1 50 101 73.7 3.9 51 101 75.1 4.0 52 101 76.3 4.0 53 101 78.8 4.1 54 101 77.5 4.1 55 101 67.8 3.6 56 Public Access 74.5 3.9 57 99 70.2 3.7 58 99 68.1 3.6 59 99 75.7 4.0 60 99 80.4 4.2 61 99 75.1 4.0 62 99 77.3 4.1 63 99 84.0 4.4 64 99 85.5 4.5 65 99 85.9 4.5 66 97 81.0 4.3 67 97 77.2 4.1 68 97 84.7 4.5 69 97 91.4 4.8 70 97 99.2 5.2 71 97 99.0 5.2 72 97 100.4 5.3 73 97 98.1 5.2 74 93 85.6 4.5 75 93 95.4 5.0 76 93 98.8 5.2 77 93 104.5 5.5 78 93 108.2 5.7 79 91 97.7 5.1 80 91 71.1 3.7 1994-2013 2003-2013 (ft)Transect Lot Page 1 of 2 Retreat (ft) Rate (ft/yr) Retreat (ft) Rate (ft/yr) 1994-2013 2003-2013 (ft)Transect Lot 81 91 31.9 3.2 82 91 20.5 2.1 83 87 13.2 1.3 84 87 22.8 2.3 85 87 55.1 5.5 86 87 76.8 7.7 87 87 84.5 8.5 88 87 81.1 8.1 89 87 61.6 6.2 90 87 48.3 4.8 91 85 67.7 6.8 92 85 67.4 6.7 93 85 61.0 6.1 94 85 60.6 6.1 95 85 54.9 5.5 96 85 59.1 5.9 97 85 66.8 6.7 98 85 72.3 7.2 99 85 67.3 6.7 100 85 67.2 6.7 101 85 67.9 6.8 102 85 64.3 6.4 103 85 64.5 6.5 Average Bank Retreat Rate by Section 4.0 5.8 Distance weight (#transects/total transects)0.7 0.3 Average Bank Retreat Rate 85-107A 4.6 Page 2 of 2 Table 3. Coastal Bank Contribution Volume for 85-107A Baxter Road Lot Retreat Rate ft/yr Section Volume cy Lot Length1 ft Weight (Lot Length/Total Project Length) Volume*Weight cy 107A 4.6 17.2 71 0.05 0.8 107 4.6 16.9 100 0.06 1.1 105 4.6 16.0 175 0.11 1.8 101 4.6 14.7 200 0.13 1.9 99 4.6 13.9 185 0.12 1.6 97 4.6 13.6 180 0.11 1.6 93 4.6 13.3 98 0.06 0.8 91 4.6 13.3 94 0.06 0.8 87 4.6 13.5 177 0.11 1.5 85 4.6 13.3 294 0.19 2.5 Total Project Length1(ft)1574 14.3 1. Length measured along the +26 MLW contour. Average Bank Contribution Volume (cy) Table 4a. WHG Sconset Bluff and Shoreline Change Data for Profiles 90, 90.6, and 91 (2006, 2008, 2013)D (ft) Z (ft, MLW) D (ft) Z (ft, MLW) D (ft) Z (ft, MLW)2006 34.6 0 -144.19 73.1 -68.59 11.72008 43.3 0 -154.89 72.31 -76.8 12.232013 50.3 0 -161.5 74.04 -75.5 9.412006 14.1 0 -128.49 81.9 -33.59 9.32008 29.5 0 -135.04 84.4 -27.85 8.932013 36.1 0 -167.04 84.86 -71.68 9.442006 21.8 0 -174.24 76.3 -71.65 8.42008 21.7 0 -174.1 76.3 -77.34 10.62013 26.2 0 -197.52 76.72 -113.61 9.64D is distance along baseline relative to 0 at benchmarkZ is elevation relative to MLW 1992Table 4E. WHG Sconset Bluff Volume Change Data for Profiles 90, 90.6, and 91 (2006-2013)ProfileDistanceftDistance Weight2006-2013 Bank Contribution Volume1cy90 425 0.254.590.6 639 0.38 17.691 622 0.37 12.4Weighted Bluff Retreat Volume12.41. Determined by calculating that volume associated with the difference in bluff positions from 2006 to 2013.Profile 90.6Profile 9169/71 Baxter Road79/81 Baxter Road91 Baxter RoadTop of BluffToe of BluffShoreline (0-MLW ft)Approximate LocationYearProfile 90 Table 5. Shoreline Change Rates from November 1994 to March 20131Profile Approximate LocationEffective Distance2ftWeight(Effective Distance  Total Distance)Shoreline Change Per Profile1 (Nov 1994-Mar2013)ftAverage Annual Shoreline Change ft(Shoreline Change/ 18.4 years)91 91 Baxter6220.43 -96.5-5.291.599/101 Baxter4310.30-58.9-3.292 105 Baxter4040.28 -45.4-2.51457Weighted average 85-107A Baxter Road-3.91. From Southeast Nantucket Beach Monitoring, March 2013, 60th Survey Report, prepared by Woods Hole Group, August 2013.2. From FEIR, Sconset Beach Nourishment Project, November 30. 2006. Attachment A, Coastal Planning and Engineering (CP&E) Engineering Design Report, Sconset Beach Nourishment Project, Nantucket, Massachusetts.Total Distance (ft) Table 6. Update of Coastal Planning & Engineering 1995-2005 Littoral Budget Analysis Profile Approximate LocationEffective Distance2ftShoreline Change Per Profile1 (Nov 1994-Mar2013)ftAverage Annual Shoreline Change ft(Shoreline Change/ 18.4 years)Top of Bank Height2 ft, MLWToe of Bankft, MLWActive Profile HeightftVolume3 (cy)91 91 Baxter 622 -96.5 -5.2 82 8 74 -894191.5 99/101 Baxter 431 -58.9 -3.2 90 8 82 -419092 105 Baxter 404 -45.4 -2.5 102 8 94 -3470Total Volume Eroded from Project Area (CY)-16601Total Volume Eroded from Project Area (CY/LF)-11.41. From Southeast Nantucket Beach Monitoring, March 2013, 60th Survey Report, prepared by Woods Hole Group, August 2013.2. From FEIR, Sconset Beach Nourishment Project, November 30. 2006. Attachment A, Coastal Planning and Engineering (CP&E) Engineering Design Report, Sconset Beach Nourishment Project, Nantucket, Massachusetts.3. Volume determined by multiplying the effective distance * active profile height * average annual shoreline change, then dividing by 27 to convert to cy (per Section 8.0 of CP&E report referenced above in #2). Attachment B Explanation of Tidal Datum Used for Siasconset Beach Dewatering Project Per Leo Asadoorian, PLS, Blackwell & Associates, Inc.; March 23, 2004 Explanation of Tidal Datum Used for Siasconset Beach Dewatering Project Per Leo Asadoorian, PLS, Blackwell & Associates, Inc. March 23, 2004 In 1994, when the beach dewatering project began, Blackwell & Associates, Inc. was contacted by Fugro East (now ENSR International) to provide elevations at monitoring wells placed in Sconset as part of preliminary investigations for a dewatering system to be placed seaward of Codfish Park. Discussions at that time with Coastal Geologist Stan Humphries, dealt with a datum that was indicative of sea level and not in the 1934 Half-Tide-Datum, which had been in use on Nantucket for 62 years. The 34 HTL datum was based on three (3) months of tide gauge readings, August – October 1934 and reduced to mean values. This datum was found not to represent actual mean sea levels due to the short duration of gauge readings. A tidal datum is usually considered to be the “average of all occurrences of a certain tidal extreme for a period of 19 years – actually 18.6 years rounded to the nearest whole year.” Obviously using the 19 - year tidal epoch would be more representative of the current sea level as opposed to the ‘34-datum. On May 23, 1994 this office received a publication dated June 5, 1992 from the National Oceanic and Atmospheric Administration (NOAA) for Nantucket Island. It correlated twelve (12) tidal benchmarks, two (2) of which also had 1934 benchmark elevations established on them, within a 16-year tidal time period. These two 1934 benchmarks, known as Tidal Benchmark No.’s 22 & 23 still exist and are in good condition. Since benchmarks 22 & 23 are within the island wide control loop established by the U.S. Coast and Geodetic Survey in 1934, it was possible to correlate any U.S.C. & G.S. benchmark on Nantucket to the 1992 adjustment provided by NOAA. All forty-four (44) monitoring stations had a 1992 tidal benchmark elevation established on them for beach profiles at each location. We have always referred to this datum as the 1992 MLW Datum, since this was the date of the NOAA publication, but the actual time period used to establish this adjustment was from 1969 through 1984. NOAA has since issued an updated publication dated April 21, 2003, which encompasses a complete tidal epoch of 19 years (Jan.1983 – December 2001). I have compared elevations of tidal data for each publication (1992 & 2001) and found them to vary by only 0.01’ to 0.03’. In summary, a local tidal benchmark system (Nantucket/Station ID 8449130) was used for this project. The NOAA tidal benchmark elevations have not been adjusted to the North American Vertical Datum of 1988 (NAVD88). The elevations established on the beach monitoring control stations are relative to Mean Low Water (MLW) and correlate with elevations for tidal benchmark No.’s 22 and 23 as published by NOAA on June 5, 1992. Attachment C Southeast Nantucket Beach Monitoring 71st Survey Report, prepared by Woods Hole Group, March 2017 SOUTHEAST NANTUCKET BEACH MONITORING March 2017 71st SURVEY REPORT 81 Technology Park Drive East Falmouth MA 02536 March 2017 Southeast Nantucket Beach Monitoring March 2017 71st SURVEY REPORT March 2017 Prepared for: Siasconset Beach Preservation Fund P.O. Box 2279 Nantucket, MA 02584 Prepared by: Mitchell Buck, P.E. and Robert P. Hamilton, Jr. Woods Hole Group 81 Technology Park Drive East Falmouth MA 02536 (508) 540-8080 Woods Hole Group Siasconset 71st Survey 2000-162 i March 2017 TABLE OF CONTENTS 1.0 INTRODUCTION .................................................................................................. 1  2.0 FEBRUARY 2017 SURVEY AND PROFILES ................................................... 3  2.1 LAND-BASED SURVEY ............................................................................................. 3  3.0 RESULTS ................................................................................................................ 7  3.1 VOLUME CALCULATIONS ......................................................................................... 7  3.1.1 November 1994 to December 2001 .......................................................... 11  3.1.2 December 2001 to September 2013 .......................................................... 11  3.1.3 September 2013 to February 2017 ............................................................ 11  3.1.4 March 2016 to February 2017................................................................... 12  3.1.5 October 2016 to February 2017 ................................................................ 12  3.2 SHORELINE CHANGE ANALYSIS ............................................................................. 12  3.2.1 November 1994 to February 2017 ............................................................ 12  3.2.2 December 2001 to February 2017 ............................................................. 13  3.2.3 September 2013 to February 2017 ............................................................ 13  3.2.4 March 2016 to February 2017................................................................... 13  3.2.5 October 2016 to February 2017 ................................................................ 13  3.3 LONG-TERM TRENDS ............................................................................................ 16  3.4 WAVE CONDITIONS ................................................................................................ 25  4.0 SUMMARY ........................................................................................................... 27  APPENDIX A – PROFILE PLOTS ............................................................................ A-1  APPENDIX B – ELECTRONIC COPY OF RAW PROFILE DATA ..................... B-1  Woods Hole Group Siasconset 71st Survey 2000-162 ii March 2017 LIST OF FIGURES Figure 1. Project Location and Profile Map ................................................................5  Figure 2. Profile for 90.6 and 91 indicating how the volume calculation region expanded for the March 2013 profiles. ........................................................8  Figure 3. Siasconset Project Area................................................................................9  Figure 4. MLW shoreline change from November 1994, December 2001, September 2013, March 2016, and October 2016 to February 2017. ..........................15  Figure 5. Cumulative Shoreline Change (ft) at Profile 84 since November 1994. ...17  Figure 6. Cumulative Shoreline Change (ft) at Profile 90 since November 1994. ...18  Figure 7. Cumulative Shoreline Change (ft) at Profile 90.6 since November 1994. 19  Figure 8. Cumulative Shoreline Change (ft) at Profile 91 since November 1994. ...20  Figure 9. Cumulative Shoreline Change (ft) at Profile 91.5 since November 1994. 21  Figure 10. Cumulative Shoreline Change (ft) at Profile 92 since November 1994. ...22  Figure 11. Cumulative Shoreline Change (ft) at Profile 92.5 since November 1994. 23  Figure 12. Cumulative Shoreline Change (ft) at Profile 93 since November 1994. ...24  Figure 13. Cumulative Shoreline Change (ft) at Profile S since November 1994. .....25  LIST OF TABLES Table 1. Profiles surveyed by date. ............................................................................6  Table 2. Volume change per profile from Nov. 1994 - Dec. 2001, Dec. 2001 - Sept. 2013, and Sept. 2013 - , Mar. 2016 -, and Oct. 2016 – Feb. 2017. ............10  Table 3. Shoreline changes from Nov. 1994, Dec. 2001, Sep. 2013, Mar. 2016, and Oct. 2016 to Feb. 2017 (Distances seaward from benchmark to 0 ft MLW92 contour). ......................................................................................14  Woods Hole Group Siasconset 71st Survey 2000-162 1 March 2017 1.0 INTRODUCTION Woods Hole Group, Inc. was contracted by the Siasconset Beach Preservation Fund (SBPF) to collect and analyze beach profile data supporting ongoing shoreline protection and monitoring efforts. This report summarizes the February 2017 topographic survey, the 71st survey conducted at Siasconset since 1994, which represents the first quarter of 2017 by current permit requirement. Woods Hole Group prepared similar data reports beginning with the 23rd survey. Previously, Coastal Planning & Engineering, Inc. (CP&E) completed more than five-years of monitoring at Siasconset, Nantucket Island, including 22 surveys, after Coastal Stabilization, Inc. (original license holder in US) installed the original beach dewatering systems in August 1994 to mitigate beach erosion. Surveys are intended to monitor beach profile and shoreline change in the region, and to plan shore protection initiatives. One of the recent initiatives includes an 852 foot long geotube system constructed between December 2013 and January 2014 to stabilize the bluff between profiles 90.9 and 91.9. The original geotube system consisted of three tiers of geotubes, and a fourth tier was added between November and December 2015 extending the northern and southern ends of the project by 21 feet and 74 feet, respectively. The monitoring program was modified to include additional profiles to monitor the shoreline fronting and adjacent to the geotubes. Quarterly shoreline monitoring is required by the geotube project’s Order of Conditions (SE 48-2824). Quarterly monitoring extends from the toe of the dune or bank seaward to the -5 ft MLW contour. Additionally, the quarterly monitoring program includes top of bank monitoring within the geotube project area and adjacent profiles 90-93. Bathymetric monitoring is required twice annually in the spring and fall quarters. Discussions are ongoing with the Nantucket Conservation Commission to optimize the monitoring program, including extent and frequency of beach profile and bathymetric surveys. Electronic copies of the raw profile data are provided on the attached CD. This report compares the recent February 2017 survey to previous data sets dating to 1994, and summarizes volume and shoreline change calculations for five time periods:  November 1994 survey through December 2001 (pre-operational period prior to the dewatering system upgrade);  December 2001 through September 2013 (post-dewatering system upgrade and pre-geotube installation period);  September 2013 through February 2017 (post-geotube installation period);  March 2016 through February 2017 (the last year); and  October 2016 through February 2017 (since last survey). September 2013 is a baseline for comparisons of pre- and post-geotube installation periods. The survey reports present new beach profile data, and compare new beach profiles to previous data. Volume calculations and shoreline change analyses lend insight to erosion and accretion trends along the beach. Woods Hole Group Siasconset 71st Survey 2000-162 2 March 2017 This report is presented in three sections plus two appendices.  Section 2.0 provides specific information regarding the current February 2017 topographic and bathymetric surveys as well as the corresponding beach profiles;  Section 3.0 presents results of the volume and shoreline change calculations and wave conditions, including a subsection on long-term trends;  Appendix A presents the plots of the profile data; and  Appendix B includes the electronic copy of raw profile data. Woods Hole Group Siasconset 71st Survey 2000-162 3 March 2017 2.0 FEBRUARY 2017 SURVEY AND PROFILES 2.1 LAND-BASED SURVEY Woods Hole Group conducted the 71st beach survey to a depth of -5 MLW from February 2nd to 3rd, 2017. Profile locations are shown on Figure 1. The horizontal datum for the project is the Massachusetts State Plane Coordinate System, Island Zone (1927) and units of feet. The vertical datum is mean low water (MLW) originally set in 1934 and corrected with 1992 NOAA adjustments by Blackwell and Associates, Inc. (BAI) (referred to hereafter as MLW92). The conversion from MLW92 to NAVD88 is -1.4 feet. Woods Hole Group conducted the February 2017 survey using a Trimble® R8 GPS receiver, a real-time kinematic global positioning system (RTK GPS) providing centimeter-level geodetic positioning. The system operates by receiving position corrections in real time from the Leica SmartNet Virtual Reference Station (VRS) network over the cellular data network. This system replaces the need for setting up a second GPS receiver as a base station on a benchmark. The system is site-calibrated to the MLW92 vertical datum using the following three (3) geodetic control points:  Station #277, a capped rebar set inside the fence by Sankaty Lighthouse at the end of Baxter Rd (N 103,724.7035, E 346,893.4132, El=109.40 MLW92).  Station #278, a capped rebar set outside the fence by Sankaty Lighthouse at the end of Baxter Rd (N 103,959.4018, E 346,817.3680, El=100.58 MLW92).  U.S. Coast Guard Disk #1, a brass disk stamped with the date 1961 located across the street from the entrance to the U.S.C.G. family housing near the former Loran tower at Low Beach (N 92,601.73, E 344,906.23, El=13.50 MLW92). Profiles were surveyed based on RTK GPS data collected along the subaerial beach profile and traditional electronic total station survey data collected in the surf-zone. At each profile, the surveyor uses the RTK GPS to navigate to previously established (but unmarked) beach monitoring benchmarks, and collects topographic profile data without having to recover and reoccupy beach monuments at each profile. The real-time horizontal positioning data is used to "steer to" the coordinates of the benchmark for each profile, and then the surveyor walks perpendicular to the bank/bluff to collect the profile data. The RTK GPS equipment limits the surveyor’s ability to wade to -5 MLW due to cabling, and is incapable of collecting wading shots due to excess movement. To remedy this, a Leica TS-02 electronic total station is utilized to survey a swimmer with a survey rod to collect the wading profile data. Table 1 lists the profiles in the monitoring program surveyed for the November 1994, December 2001, September 2013, March 2016, October 2016, and February 2017 surveys. All surveyed profiles reached the target depth of -5 MLW except profiles Q1 and Q2 due to an unrecoverable instrument malfunction. Profiles not reaching the target depth are extrapolated using the average offshore slope presented in the baseline erosion rates report. A visual assessment of the profiles reveals the extrapolated profile sections compare well in shape with previous profiles, and indicates volume calculations effectively characterize the beach changes. Previous surveys showed the extrapolation Woods Hole Group Siasconset 71st Survey 2000-162 4 March 2017 method adequately characterizes the beach profile, which is relatively consistent, steep, and linear on this section of coast. As further explained in Section 3, ongoing erosion afforded surveys of certain profiles extending landward of earlier 1994 and 2001 profile baselines, providing data for more informative volume calculations farther landward when comparing the most recent data sets. The “Distance” column in Table 1 represents the landward distance from the original benchmarks where volume calculations were possible between the two most recent surveys. The September 2012 survey (not shown) established a new landward baseline for comparison at certain profiles. Red numbers represent beach profiles where volume change was calculated farther landward than in previous reports. Woods Hole Group Siasconset 71st Survey 2000-162 5 March 2017 Figure 1. Project Location and Profile Map Woods Hole Group Siasconset 71st Survey 2000-162 6 March 2017 Table 1. Profiles surveyed by date. PROFILE Baseline SURVEY DATE NAME Distance2 (ft) Nov-94 Dec-01 Sep-13 Mar-16 Oct-16 Feb-17 81 -200      82 -70       83 -20       84 -20       84.3 0       84.6 0       85 0       86 -30       87 -75       88 -130       88.6 -110       89 -167       89.2 -98       89.5 -89       89.8 -72       90 -102       90.6 -59       90.81 NS NS NS NS    90.851 NS NS NS NS    90.91 NS NS NS NS    90.951 NS NS NS NS   91 -111   91.21 NS NS NS NS   91.351 NS NS NS NS   91.5 -72   91.91 NS NS NS NS   92 -68       92.11 NS NS NS NS    92.21 NS NS NS NS    92.5 -53       93 -26       93.5 -50       94 -52       95 -54       95.5 -56       96 -33       96.5 -19       97 -11       98 0       99 0       Q -24       Q11 NS NS NS NS    Q21 NS NS NS NS    S 0       S11 NS NS NS NS    W -30       SHADING indicates the geotube project area Note that historical profiles 82.6, 83.5, 86.5, 87.4, 87.5, 88.3, 96.7, 96.9, 97.6, and 97.3 and the September 2013 profiles 89.3, 89.4, 89.6, 92.8, 92.9, 93.2, and 93.8 were removed in April 2014 from the monitoring program and therefore were not surveyed. NS = Not Surveyed; RED NUMBER = profile using updated volume calculation windows; 1 = Profile added in April 2014. 2 = Distance is landward extent of the profile used for volume calculations. Woods Hole Group Siasconset 71st Survey 2000-162 7 March 2017 3.0 RESULTS 3.1 VOLUME CALCULATIONS Volume calculations were performed using MATLAB, and are presented in this report for these time periods:  November 1994 to December 2001 (the dewatering system pre-operational period);  December 2001 to September 2013 (the pre-geotube installation period);  September 2013 to February 2017 (the post-geotube installation period);  March 2016 to February 2017 (the last year); and  October 2016 to February 2017 (the duration since the last survey). These surveys characterize volume change in the profile from the seaward position of the –5 ft isobath, landward to the toe of the dune (Xon). Volume calculations were computed from a landward limit (“baseline distance”), as specified in Table 1, to an offshore depth of –5 ft MLW. This baseline distance location was determined based on the toe of bank locations for the December 2001 pre-operational survey (where applicable) or as far back as data were available for comparison with other surveys. Specific profiles were also translated horizontally to account for movement of the benchmarks over time as the beach eroded in certain places (i.e., the 0 point in the field is the stake location, which had changed). Some of these translations are cumulative since December 2001, as five benchmarks were relocated between December 2002 and March 2003 (profiles 81, 87.5, 88.3, 91, and 93), documented in the 32nd report. A different set of baseline distances was specified for comparisons with November 1994, since surveys at that time did not extend landward of the benchmarks (original baseline). For profiles 91 and 91.5, the baseline distance was modified from 0 ft to -20 ft because the ground survey in December 2001 did not extend landward beyond the toe of dune. Progressive erosion of the profiles since 2001 resulted in a scenario where the active portion of certain profiles retreated landward of the baseline distance within which original volume calculations were made. Figure 2 shows an example for profiles 90.6 and 91; the vertical dashed lines indicate the region where volume calculations were made in prior reports. Prior to 2001, the “Old” area shown in Figure 2 represented the active profile; however, prevailing erosion produced a scenario where recent volume calculations limited to within the Old baseline distance do not represent overall profile change, since a significant portion of the active berm extends landward of the Old baseline. For instance, volume change for several profiles known to have eroded substantially would result in a positive volume change calculation incorrectly indicating accretion if limited within the Old baseline distance. This trend exists for other profiles, but is not consistent across all profiles. To better characterize beach change, a new method was established in 2013 whereby volume calculations were extended landward as needed to more accurately represent beach volume change starting in March 2013 (using the September 2013 as the new baseline). The seaward limit of -5ft MLW isobath was maintained, while the landward limit of the profile was extended as far landward as practical to compare recent profiles (“New” distance shown by Figure 2). The adjusted Woods Hole Group Siasconset 71st Survey 2000-162 8 March 2017 profiles are highlighted red in column two of Table 1. The new results are not directly comparable to calculations made for prior time periods in previous reports, but more accurately represent recent dynamic beach response. Figure 2. Profile for 90.6 and 91 indicating how the volume calculation region expanded for the March 2013 profiles. Volume and shoreline change were calculated for the profiles in the entire monitoring area (profiles 81 to W). The historical project area was defined as the area extending from profile 89.2 through profile 92.5 (Figure 3) with two mitigation areas, 1,000 ft to both sides of the previous Lighthouse Beach dewatering system site, included in the definition of the project area. Historically, profiles 90, 90.6 and 91 were used to calculate the treated area changes, profiles 89.2, 89.5, 89.8, 90 and 90.6 were used to calculate the south mitigation area changes, and profiles 90.6, 91, 91.5, 92, and 92.5 were used to calculate the north mitigation area changes. Since the dewatering system is no longer performing, the definition of the project area has been modified to indicate the boundaries of the geotube monitoring area between profiles 88 and 94 and the actual geotube project area with a footprint between profiles 90.9 and 91.9. Old New New Old Woods Hole Group Siasconset 71st Survey 2000-162 9 March 2017 Table 2 lists the volume change for each profile for each time period. Volume calculations for the twelve (12) new profiles were only calculated for the most recent periods since the profiles were added in April 2014. Results are summarized below. Figure 3. Siasconset Project Area Woods Hole Group Siasconset 71st Survey 2000-162 10 March 2017 Table 2. Volume change per profile from Nov. 1994 - Dec. 2001, Dec. 2001 - Sept. 2013, and Sept. 2013 - , Mar. 2016 -, and Oct. 2016 – Feb. 2017. (+ Accretion, - Erosion) (N/A: Not Available) SHADING indicates the geotube project area VOLUME CHANGE PER PROFILE PROFILE Nov-94 to Dec-01 (cy/ft) Dec-01 to Sept-13 (cy/ft) Sep-13 to Feb-17 (cy/ft) Mar-16 to Feb-17 (cy/ft) Oct-16 to Feb-17(cy/ft) 81 -69 13.6 -17.4 -11.4 16.6 82 -31.7 31.6 -11.4 11.9 -1.6 83 47.7 25.5 -16.0 -16.3 -12.7 84 11.8 54.4 7.3 -3.2 -3.3 84.3 14.1 36.6 12.1 0.3 3.2 84.6 36.4 4.5 11.1 6.8 6.0 85 39.4 -23.5 6.9 7.3 5.6 86 4 -20.5 -9.3 1.3 3.9 87 -56 -22.3 -19.3 -3.9 1.6 88 -41.5 -50 4.3 1.3 5.4 88.6 -48.8 -33.5 0.9 1.4 6.0 89 -55.5 -18.9 -0.5 1.2 7.7 89.2 -60.7 -17.8 -2.9 -4.2 1.0 89.5 -65.2 -13.7 -4.6 -7.5 -0.8 89.8 -67.9 -9.5 -10.4 -11.5 -5.8 90 -61.5 -7.3 -7.0 -9.6 -6.1 90.6 -51.6 -8.7 -11.1 -7.6 -3.5 90.8 N/A N/A N/A -6.7 -1.5 90.85 N/A N/A N/A -5.6 -0.6 90.9 N/A N/A N/A -5.1 -0.8 90.95 N/A N/A N/A -3.1 1.2 91 -42 -14.1 -6.6 -5.3 -1.4 91.2 N/A N/A N/A -0.6 2.0 91.35 N/A N/A N/A -1.9 1.0 91.5 -21.1 -24.6 -5.1 -2.5 -0.5 91.9 N/A N/A N/A -2.2 -2.2 92 -12.5 -13.7 -6.1 1.4 2.4 92.1 N/A N/A N/A -0.8 1.3 92.2 N/A N/A N/A -2.3 -1.6 92.5 -21.1 -0.8 -5.3 7.1 5.7 93 -30.9 2.4 -8.1 -0.6 4.6 93.5 -35.7 5.5 -7.1 -1.8 1.2 94 -25.9 -4.5 -10.5 -5.9 -1.5 95 -25.3 -12.9 -17.3 -6.2 -0.8 95.5 -33.2 -22.3 -15.6 -4.1 0.5 96 -6.2 -16.9 -18.9 -7.1 -0.9 96.5 -1.9 -2.4 -14.9 -6.6 -2.4 97 -7.2 18.3 -6.7 -4.2 0.9 98 -0.3 12.7 -4.2 -0.4 -4.1 99 -1.9 19.7 -0.6 -0.6 -0.2 Q 6.7 -5 -5.4 1.8 3.0 Q1 N/A N/A N/A 3.3 3.8 Q2 N/A N/A N/A 7.0 6.8 S 21.4 14.9 2.8 6.6 8.9 S1 N/A N/A N/A 6.6 6.0 W 16.5 13 10.7 8.6 13.2 Woods Hole Group Siasconset 71st Survey 2000-162 11 March 2017 3.1.1 November 1994 to December 2001 This period, traditionally known as the dewatering system pre-operational period, is included for historical consistency, and extends from the earliest dewatering system pre- construction survey to the December 2001 survey before the (now not operating) dewatering system upgrade.  The central portion of the monitoring area eroded (profile lines from 87 through 99), from just north of Codfish Park to Sesachacha Pond. Maximum erosion was focused between profiles 87 and 91, where total erosion since 1994 exceeded -40 cy/ft; with a maximum of -68 cy/ft of erosion at profile 89.8.  The southern profiles, characterized by profiles 83 through 86, accreted with the exception of the southern-most profiles 81 and 82. Maximum accretion exceeded 47 cy/ft at profile 83.  The beach was relatively stable and accreting from profiles Q through W. 3.1.2 December 2001 to September 2013 This period, also reported for historical context and consistency, extends from the activation of the upgraded dewatering system through the last survey prior to geotube installation (September 2013). Table 2 presents volume change for the monitoring area. The monitoring area performed as follows:  The southern portion of the monitoring area, from profile 81 through profile 84.6, gained sediment over the 12 years.  Maximum accretion occurred at profile 84, where more than 54 cy/ft of sediment accumulated in the 12 years.  The central portion of the study area, between profiles 85 through 92.5 eroded.  Maximum erosion of -50 cy/ft occurred at profile 88.  In the northern reach, beach volume was stable or accreted from profile 97 to W except profile Q (between ~12 to 19 cy/ft of accretion). 3.1.3 September 2013 to February 2017 This period spans the period since the installation of the geotubes; September 2013 has been established as a baseline survey. Table 2 presents the results. The monitoring area performed as follows:  Of the 34 profiles surveyed in the monitoring area, erosion was the dominant trend with 26 profiles eroding and 8 profiles accreting since the geotubes were installed. Note that in September 2013 only 34 of the current 46 profiles were included in the monitoring program and can be used for comparison.  Maximum erosion occurred at profile 87, which eroded more than -19 cy/ft.  Accretion ranging from 1 to 12 cy/ft was focused between profiles 84 to 88.6, excepting 86 and 87, in Codfish Park. Woods Hole Group Siasconset 71st Survey 2000-162 12 March 2017  Profiles 91 and 91.5 in the geotube project area eroded between -5.1 to -6.6 cy/ft since the geotubes were installed. 3.1.4 March 2016 to February 2017 This period spans the duration since the last annual survey in March 2016. Table 2 presents the results. The monitoring area performed as follows:  Of the 46 profiles surveyed in the monitoring area, erosion was the dominant trend with 30 profiles eroding and 16 profiles accreting since the last annual survey.  Erosion occurred along most of the project area, with a maximum erosion of nearly -16.3 cy/ft at profile 83.  All 6 profiles in the geotube project area eroded since the last year, with a maximum erosion of -5.3 cy/ft at profile 91. 3.1.5 October 2016 to February 2017 This period spans the duration since the last survey in October 2016. Table 2 presents the results. The monitoring area performed as follows:  Of the 46 profiles surveyed in the monitoring area, 20 profiles eroded and 26 profiles accreted since the last survey.  Erosion occurred primarily in the central part of the project area, but with maximum erosion of nearly -13 cy/ft at profile 83.  Accretion occurred in both the north and south of the project area, with maximum accretion of 16.6 cy/ft at profile 81.  Of the six profiles in the geotube project area, three accreted and three eroded. 3.2 SHORELINE CHANGE ANALYSIS Woods Hole Group evaluated shoreline change (retreat or advance of the mean low water line) to provide insight regarding beach response in the project vicinity. This section provides a comparison of shoreline changes in the monitoring area since November 1994 for the five (5) periods under investigation. Shoreline distances were measured from the baseline horizontally to the 0 ft MLW92 contour level for consistent comparison with prior reports. Table 3 lists shoreline change by profile for the surveys under investigation. Figure 4 illustrates shoreline change. Results can be summarized as follows: 3.2.1 November 1994 to February 2017  Except for the extreme southern limit of the monitoring area, the shoreline advanced in the southern portion of the monitoring area (profiles 83 to 85), Woods Hole Group Siasconset 71st Survey 2000-162 13 March 2017 retreated in the middle (profiles 86 to 96.5), and accreted at the northern portion (profiles 97 to W, except Profile Q) since the surveys began in 1994.  Maximum shoreline advance occurred between profiles 83 and 85, where the shoreline advanced more than 125 ft at profile 84.  Maximum shoreline retreat occurred between profiles 87 and 91, where the shoreline retreated more than -113 ft. 3.2.2 December 2001 to February 2017  Except the extreme southern limit of the survey area, the shoreline change trend since December 2001 is similar to the trend since 1994. The southern and northern limits accreted while the middle of the monitoring retreated.  Shoreline advance since December 2001 occurred between profiles 81 and 84.6, except profile 83, with a maximum shoreline advance of nearly 106 ft at profile 84.  Shoreline retreat since December 2001 occurred between profiles 85 and 96.5, except profile 93.5, with a maximum shoreline loss of more than -64 ft at profile 87. 3.2.3 September 2013 to February 2017  Shoreline recession has been the dominant trend since the geotubes were installed with 26 profiles retreating and 8 profiles accreting since the September 2013 survey. Note that in September 2013 only 34 of the current 46 profiles were included in the monitoring program and can be used for comparison.  The maximum shoreline advance was 23.3 ft at profiles 84.3.  The maximum shoreline retreat was -42.9 ft at profile 87. 3.2.4 March 2016 to February 2017  Overall, shoreline recession was the dominant trend with 36 profiles retreating and 10 profiles accreting over the past year since March 2016.  Accretion occurred between 82 and 89 (excepting 83, 84, and 8), 92.5, and Q2, with a maximum accretion of 30.0 ft at profile 82.  Maximum shoreline retreat in the past year was -36.2 ft at profile 83.  All six (6) profiles in the geotube project area eroded during the last year. 3.2.5 October 2016 to February 2017  Shoreline accretion was the dominant recent trend since the last survey with 31 profiles advancing and 15 profiles retreating.  Maximum shoreline advance in the past three months occurred at profile 81, advancing 76.0 ft.  Maximum shoreline retreat in the past three months occurred at profile 83, retreating -18.0 ft.  Of the six (6) profiles in the geotube project area, only profile 91.9 retreated at -7.3 ft, while the other profiles advanced 0.4 to 6.9 ft. Woods Hole Group Siasconset 71st Survey 2000-162 14 March 2017 Table 3. Shoreline changes from Nov. 1994, Dec. 2001, Sep. 2013, Mar. 2016, and Oct. 2016 to Feb. 2017 (Distances seaward from benchmark to 0 ft MLW92 contour). PROFILE SHORELINE CHANGE PER PROFILE Nov-94 to Feb-17 (ft) Dec-01 to Feb-17 (ft) Sep-13 to Feb-17 (ft) Mar-16 to Feb-17 (ft) Oct-16 to Feb-17(ft) 81 -125.6 3.1 -11.2 -3.3 76.0 82 -4.2 39.6 -29.0 30.0 6.1 83 84.9 -0.2 -40.1 -36.2 -18.0 84 125.4 106.4 11.3 -2.9 -2.4 84.3 104.3 80.5 23.3 0.4 12.2 84.6 79.8 27.6 22.8 17.9 14.9 85 45.2 -17.1 13.2 14.5 13.2 86 -42.9 -48.2 -8.4 7.3 13.5 87 -158.7 -64.4 -42.9 -3.4 7.4 88 -121.1 -53.1 4.6 3.7 14.2 88.6 -122.6 -36.4 2.5 2.5 14.2 89 -122.9 -26.6 0.3 1.9 20.0 89.2 -120.5 -22.2 -4.3 -1.9 10.3 89.5 -120.0 -20.6 -10.2 -10.8 4.8 89.8 -130.3 -23.2 -16.2 -14.7 -5.3 90 -133.9 -26.1 -16.3 -16.2 -6.7 90.6 -113.5 -31.6 -23.4 -11.7 -5.0 90.8 N/A N/A N/A -11.7 1.5 90.85 N/A N/A N/A -9.3 0.2 90.9 N/A N/A N/A -10.3 -0.6 90.95 N/A N/A N/A -6.7 3.2 91 -113.9 -24.0 -22.2 -6.7 4.6 91.2 N/A N/A N/A -0.2 6.9 91.35 N/A N/A N/A -3.0 3.8 91.5 -84.6 -17.3 -23.8 -3.1 0.4 91.9 N/A N/A N/A -3.9 -7.3 92 -65.1 -46.8 -13.2 -2.3 -0.7 92.1 N/A N/A N/A -1.3 2.0 92.2 N/A N/A N/A -12.4 -4.9 92.5 -45.8 -5.2 -4.2 8.8 9.6 93 -47.5 -3.0 -6.2 -5.0 9.1 93.5 -61.6 3.2 -4.9 -7.3 10.0 94 -60.3 -19.7 -10.8 -8.9 5.3 95 -83.8 -41.8 -18.9 -9.2 2.2 95.5 -96.3 -60.8 -19.8 -5.0 3.4 96 -79.2 -47.2 -29.9 -14.4 -1.9 96.5 -29.3 -24.2 -22.0 -12.5 -4.0 97 5.1 14.8 -9.2 -11.1 0.8 98 4.3 5.5 -5.2 -2.0 -7.2 99 16.4 17.0 -5.6 -7.2 -2.1 Q -11.1 -10.5 -3.0 -1.0 0.7 Q1 N/A N/A N/A -0.8 -1.3 Q2 N/A N/A N/A 3.4 3.7 S 24.0 3.7 -9.5 -4.6 3.8 S1 N/A N/A N/A -1.6 2.5 W 13.1 9.6 0.4 -14.5 -0.3 (N/A: Not Available) SHADING indicates geotube project area Woods Hole Group Siasconset 71st Survey 2000-162 15 March 2017 Note: Shoreline change is interpolated for transects where data are unavailable Figure 4. MLW shoreline change from November 1994, December 2001, September 2013, March 2016, and October 2016 to February 2017. Woods Hole Group Siasconset 71st Survey 2000-162 16 March 2017 3.3 LONG-TERM TRENDS To help visualize long-term trends at select profiles along the monitoring area, the Woods Hole Group put together a series of figures showing the cumulative shoreline change (feet) in shoreline position relative to a 1994 baseline position (zero on the vertical axis) over time on the horizontal axis for a representative subset of beach profiles. The figure captions include profile-specific observations. The nine (9) beach profiles shown in Figure 5 through 12 represent the stretch of beach subject to monitoring including:  Near the south of the monitoring area (Profile 84)  Approximately 1,000 ft and 500 ft south of the geotubes (Profiles 90 and 90.6)  Within the geotube area (Profiles 91, 91.5 and 92)  Approximately 500 ft and 1000 ft north of the geotubes (Profiles 92.5 and 93)  Near the north end of the monitoring area (Profile S) Individual data points on each plot represent the change in shoreline position at mean low water (MLW), based on the surveyed beach profile at that time. Positive numbers indicate shoreline advance and negative numbers indicate shoreline retreat relative to the 1994 baseline (assumed zero). On the figures, blue dots represent data obtained from surveys before the installation of geotubes. Red dots represent data obtained from surveys obtained after the installation of geotubes. Based on the data presented below, the shoreline response since the geotubes were installed is not materially different from other shoreline responses measured in the past. However, the project installation year provides a known geographic and temporal reference point, is subject to the current regulatory requirements, and is expected to be subject to future monitoring. The plots demonstrate the temporal variability and show:  Periods of stability when there is little cumulative change in shoreline position as seen in Figure 5 from December of 1996 to May of 2002;  Periods of shoreline advance as seen in Figure 5 from May 2002 to February 2005; and  Periods of shoreline retreat as seen in Figure 6 from December 1996 to February 2005. General observations derived from the data plotted on Figures 5 through 13 are summarized below. This collection of long-term observations accentuates the high degree of variability at this site, and indicates that recent shoreline changes are similar to changes that occurred in the past:  Each profile includes times of shoreline advance and shoreline retreat, demonstrating a high degree of variability on short and long time scales. This high degree of variability, with observed short-term periods of erosion or accretion, suggests that adverse effects from the geotextile tubes could only be reliably determined through the prevalence of sustained periods (2 years or more) of shoreline erosion exceeding historic observations. Woods Hole Group Siasconset 71st Survey 2000-162 17 March 2017  Each profile responds differently on variable time scales.  This variability does not lend itself to fitting a long-term trend line with a high degree of statistical accuracy.  The current (February, 2017) shoreline position is generally similar (within about 20 feet) to the shoreline position in the ~2005-2008 timeframe, although there is substantial variability (up to 50 feet of cumulative difference) between these dates (which may be a result of short-term storm events, such as Hurricane Irene in August 2011 and Superstorm Nemo in February 2013).  The short-term variability shown by surveys since geotube installation in January 2014 is similar to short-term variability (~2-3 year periods) observed over many years of surveys before the geotubes were installed. Surveyed post-geotube shoreline changes are not materially different from previous observations as related to rates and duration of shoreline change. No accelerated erosion in excess of historical observations is evident. Figure 5. Cumulative Shoreline Change (ft) at Profile 84 since November 1994.  Overall shoreline advance of ~130 ft since 1994  Relatively stable shoreline position from 1996 to late 2001  200 ft of shoreline advance from September 2001 to January 2004  Variable alternating periods of relative stability with modest shoreline advance and retreat spanning multiple years since 2004  Current shoreline position similar to 2008; an observation also noted for other profiles Woods Hole Group Siasconset 71st Survey 2000-162 18 March 2017  Recent trend of shoreline advance since October 2014; similar periods of shoreline advance on the order of 30 ft also experienced from October 2008 to March 2012 and from February 2005 to August 2006 Figure 6. Cumulative Shoreline Change (ft) at Profile 90 since November 1994.  Variable periods of shoreline retreat, stability, and advancement  Net shoreline erosion on the order of -120 ft since 1994  Relatively consistent erosion from 1996 through April 2001;  Sharper short-term shoreline retreat between June 2005 and February 2006  Shoreline advance from February 2006 to November, 2007  Substantial reversing trend of beach accretion from April 2011 to April 2014  Current shoreline position similar to 2007; an observation common to other profiles  Recent trend of shoreline retreat since April 2014; similar to the rate experienced from September 1998 to December 2001 Woods Hole Group Siasconset 71st Survey 2000-162 19 March 2017 Figure 7. Cumulative Shoreline Change (ft) at Profile 90.6 since November 1994.  Variable periods of shoreline erosion, stability, and accretion  General trend of shoreline erosion between 1996 and 2003  Substantial advance from October 2003 to February 2005  Sharp retreat from 2005 to 2006  Net shoreline retreat on the order of -100 ft since 1994  Recent trend of shoreline erosion since April 2014; similar periods experienced previously in 1998-2000 and 2005-2006  Current shoreline position similar to 2007; an observation common to other profiles Woods Hole Group Siasconset 71st Survey 2000-162 20 March 2017 Figure 8. Cumulative Shoreline Change (ft) at Profile 91 since November 1994.  Net shoreline loss since 1994 on the order of -110 ft  Substantial trend of beach erosion at variable rates through 2007  Variable shoreline position since 2005 with reversing trends of beach accretion and erosion  Substantial shoreline advance from September 2012 to March 2013  Little net change in the shoreline position since April 2007; similar to other profiles  Current trend of beach retreat since September 2013  Similar shoreline erosion measured also in September 2010 to September 2012, October 2003 to June 2005, and December 1998 to June 2000 Woods Hole Group Siasconset 71st Survey 2000-162 21 March 2017 Figure 9. Cumulative Shoreline Change (ft) at Profile 91.5 since November 1994.  Net shoreline retreat on the order of -75 ft since 1994  Relatively consistent long-term shoreline erosion from 1996 through September 2012; with short-term variability  Substantial beach accretion occurred from September 2012 to March 2013  Current shoreline position similar to December 2006; the observation that the current shoreline position is similar to the condition 8-10 years ago is common to other profiles  Recent trend of beach stability since October 2015 Woods Hole Group Siasconset 71st Survey 2000-162 22 March 2017 Figure 10. Cumulative Shoreline Change (ft) at Profile 92 since November 1994.  Highly variable shoreline position  Net erosion on the order of -60 ft since 1994  Current shoreline position similar to observations since 2005; similar to other profiles  Recent trend of beach stability since October 2015 Woods Hole Group Siasconset 71st Survey 2000-162 23 March 2017 Figure 11. Cumulative Shoreline Change (ft) at Profile 92.5 since November 1994.  Highly variable shoreline position  Net erosion on the order of -50 ft since 1994  Current shoreline position similar to observations since 2005; similar to other profiles  Recent trend of beach stability since October 2015 Woods Hole Group Siasconset 71st Survey 2000-162 24 March 2017 Figure 12. Cumulative Shoreline Change (ft) at Profile 93 since November 1994.  Relatively stable shoreline position since 1998  Majority of net losses occurred between 1994 and 1998  Current shoreline position similar to the envelope since 2005  Recent short-term variability in the shoreline position similar to past short-term variations Woods Hole Group Siasconset 71st Survey 2000-162 25 March 2017 Figure 13. Cumulative Shoreline Change (ft) at Profile S since November 1994.  Net shoreline advance on the order of 25 ft since 1994  Majority of accretion occurred up to 2010  Relatively stable but variable shoreline position since 2005; as with other profiles, the current shoreline position is almost identical to 2006 3.4 WAVE CONDITIONS The 71st survey is defined by the time period of October 29, 2016 through February 1, 2017. Nearshore wave data for this time period was obtained from the Woods Hole Oceanographic Institution’s (WHOI) Martha’s Vineyard Coastal Observatory (MVCO), located approximately 1.5 kilometers south of Edgartown Great Pond in 12 meters of water. The MVCO collects wave data every 20 minutes, and the data are freely available from their website (http://www.whoi.edu/mvco/). At the location of the MVCO, waves arrive primarily from West-Southwest to East-Southeast, with the majority arriving from the South. This is expected since the waves refract toward a shore-normal approach to the southern-facing shoreline of Martha’s Vineyard. The MVCO station was shut down for maintenance on July 17, 2016 and service was restored on September 22nd. The wave sensor went offline shortly thereafter and has since not been repaired. WHOI indicated that the wave sensor is scheduled to be repaired in the spring 2017. Offshore wave data is typically obtained from the National Oceanic and Atmospheric Administration’s (NOAA’s) National Data Buoy Center (NDBC) Station 44008, located 54 nautical miles southeast of Nantucket Island in 62.5 meters of water. NDBC Station 44008 records data for a 20-minute sampling period every hour. However, this station Woods Hole Group Siasconset 71st Survey 2000-162 26 March 2017 ceased transmissions after October 10th as the remnants of Hurricane Mathew passed through the area and a later reconnaissance determined that no buoy was on station. NOAA indicated this station is on the future maintenance schedule for replacement; therefore, wave data from station 44008 is not available during this period. As there was little data to no available for either station, wave data was not assessed during this time period. Wave data should be available for the next scheduled quarterly survey during spring 2017. Woods Hole Group Siasconset 71st Survey 2000-162 27 March 2017 4.0 SUMMARY The Winter 2017 quarterly survey included collection of topographic and bathymetric survey data, and the resulting transect profiles are plotted in Appendix A. From the analysis of the data collected for the 71st survey (February 2017), the following summary can be made:  Wave data was not available for either the offshore NOAA station 44008 or the nearshore MVCO station because both sensors were either inoperable or missing. According to the parent organizations, both stations should be restored by the next quarterly survey (spring 2017).  Low Beach at profiles 81 and 82 continues to exhibit extremely variable shoreline change.  Since the geotubes were installed in September 2013, 26 of the 34 profiles have eroded throughout the monitoring area. Within the geotube project area, profiles 90.9 to 91.9, volume loss and shoreline retreat have been the dominant trend which is consistent with the rest of the monitoring area.  In the past year, erosion has been the dominant trend as 30 of the 46 profiles in the entire monitoring area lost beach volume and 36 profiles lost beach width.  Since the last survey in October 2016, the dominant regional trend for beach volume change was accretion (31 accreting and 15 eroding) and shoreline advance. This is not typical for a winter profile, but the shoreline of Siasconset was significantly impacted by two hurricanes, Hermine and Matthew, in the fall of 2016 as reported during the last 70th Quarterly October 2016 report. It was documented that the storms had caused erosion along 43 of the 46 profiles, which was unexpected for post-summer beach profiles. It is possible that the beaches have been recovering from the storm impacts as the sand eroded by the storms is distributed along the beaches. Substantial natural variability is characteristic of the region depending upon prevailing conditions. Woods Hole Group Siasconset 71st Survey 2000-162 A-1 March 2017 APPENDIX A – PROFILE PLOTS Woods Hole Group Siasconset 71st Survey 2000-162 B-1 March 2017 APPENDIX B – ELECTRONIC COPY OF RAW PROFILE DATA Attachment D 2001-2007 Wetland Well Monitoring Data Transect Lot Bank Retreat 1994-2013 (ft) Bank Retreat 2003-2013 (ft) NORTH CONTROL AREA 1 119 26.19 2 119 24.06 3 119 28.10 4 119 25.72 5 117 28.21 6 117 29.35 7 117 25.88 8 117 20.53 9 117 24.68 10 117 30.79 11 115 29.74 12 115 25.69 13 115 25.87 14 115 20.98 15 115 30.76 16 113 35.10 17 113 36.12 18 113 28.31 19 113 25.38 20 113 29.07 21 109 25.74 22 109 26.24 23 109 24.15 24 109 30.21 25 109 48.68 26 109 55.92 27 109 52.49 28 109 51.87 29 109 47.26 30 107A 46.15 31 107A 43.91 32 107A 47.46 33 107 51.08 34 107 56.18 35 107 53.84 36 107 57.67 37 107 57.25 38 105 50.17 39 105 50.00 40 105 58.46 41 105 82.29 41 38.2 2.0 SOUTH CONTROL AREA 91 85 67.72 92 85 67.36 93 85 60.96 94 85 60.55 95 85 54.88 96 85 59.06 97 85 66.80 98 85 72.34 99 85 67.27 100 85 67.24 10 64.4 6.4CONTROL AREA AVERAGE Weighted average retreat for North and South Control (ft/yr)2.9 Location Top of Bank (ft MLW)Toe of Bank (ft MLW)Bank Height above Toe (ft) 119 Baxter 104 11 93 117 Baxter 105 11 94 115 Baxter 105 11 94 113 Baxter 103 11 92 109 Baxter 101 11 90 107A Baxter 100 11 89 107 Baxter 98 11 87 105 Baxter 93 11 82 85 Baxter 78 11 67 Average height 87.6 Standard Calculation of Compensatory Mitigation Bank Retreat (ft)Bank Height (ft)Mitigation Volume (cy) ((Retreat * Height)/27)) 2.9 88 Bank Height 9.3 BANK RETREAT CALCULATIONS FOR NORTH & SOUTH CONTROL AREAS CONTROL AREAS - STANDARD CALCULATION OF BANK CONTRIBUTION VOLUME # TRANSECTS AVERAGE AVERAGE ANNUAL RETREAT (FT/YR) # TRANSECTS AVERAGE AVERAGE ANNUAL RETREAT (FT/YR) Transect Lot Bank Retreat 1994-2013 (ft) Bank Retreat 2003-2013 (ft) 43 105 79.80 44 105 77.42 45 105 75.89 46 105 74.74 47 101 79.44 48 101 76.83 49 101 77.28 50 101 73.68 51 101 75.07 52 101 76.28 53 101 78.83 54 101 77.47 55 101 67.77 56 Public Access 74.51 57 99 70.24 58 99 68.06 59 99 75.69 60 99 80.43 61 99 75.06 62 99 77.30 63 99 84.02 64 99 85.45 65 99 85.86 66 97 81.02 67 97 77.16 68 97 84.74 69 97 91.43 70 97 99.19 71 97 99.03 72 97 100.42 73 97 98.05 74 93 85.60 75 93 95.37 76 93 98.80 77 93 104.46 78 93 108.22 79 91 97.67 80 91 71.14 81 91 31.87 82 91 20.52 83 87 13.15 84 87 22.83 85 87 55.13 86 87 76.78 87 87 84.53 88 87 81.09 89 87 61.64 90 87 48.33 # TRANSECTS 38 AVERAGE TRANSECTS 43-80 83.1 AVERAGE ANNUAL RETREAT (FT/YR)4.4 # TRANSECTS 10 AVERAGE TRANSECTS 81-90 49.6 AVERAGE ANNUAL RETREAT (FT/YR)5.0 GEOTUBE AREA WEIGHTED AVERAGE ANNUAL RETREAT 4.5 Location Top of Bank (ft MLW)Toe of Bank (ft MLW)Bank Height above Toe (ft) 105 Baxter 93 10 83 101 Baxter 85 10 75 99 Baxter 80 10 70 97 Baxter 78 10 68 93 Baxter 78 10 68 91 Baxter 74 10 64 87 Baxter 77 10 67 Average height (ft)71 Bank Retreat (ft)Bank Height (ft) 4.5 71 Standard Calculation of Compensatory Mitigation 11.8 GEOTUBE AREA - STANDARD CALCULATION OF BANK CONTRIBUTION VOLUME BANK RETREAT CALCULATIONS FOR GEOTUBE AREA GEOTUBE AREA Mitigation Volume (cy) ((Retreat * Height)/27)) Bank Height Attachment E Bank Retreat Calculations for North and South Control Areas Average Minimum Maximum May 14, 2001 Jun 14, 2001 July 25, 2001 Aug 19, 2001 Sep 17, 2001 Oct 18, 2001 Nov 21, 2001 Dec 23, 2001 Well E-1 6.82 5.04 7.35 6.8 7.35 5.05 5.65 5.04 7.18 7.17 7.15 Well E-2 3.32 1.75 4.22 2.18 1.75 4.22 3.95 3.75 4.11 3.96 4.19 Well E-3 7.61 5.85 8.30 6.15 5.85 6.08 7.5 7.72 8.25 8.3 Well E-4 6.43 3.62 7.68 5.41 4.3 3.62 4.12 7.35 6.68 7.42 7.4Well E-5 4.75 1.33 7.08 4.93 4.05 4.12 4.53 5.31 7.06 7.07 7.08Well E-6 3.83 1.42 6.90 6.9 2.8 2.65 2.85 4.45 5.92 6.47 3.27Well E-7 6.27 2.80 12.50 12.5 11.5 8.4 9.25 9.3 9.7 9.33 10.22Well E-8 5.22 3.15 7.95 7.82 4.75 5.75 6.38 6.4 6.94 5.24 7.35 Table 1. Depths of Groundwater (ft) in Wetlands Monitoring Wells (2001-2007) Average Well E-1 6.82 Well E-2 3.32 Well E-3 7.61 Well E-4 6.43 Well E-5 4.75 Well E-6 3.83 Well E-7 6.27 Well E-8 5.22 Jan 28, 2002 Feb 26, 2002 Mar 30, 2002 May 8, 2002 May 24, 2002 June 26, 2002 July 30, 2002 Aug 30, 2002 Oct 2, 2002 Oct 29, 2002 7.15 7.15 7.15 7.14 7.19 7.13 7.1 7.12 7.1 7.15 3.95 3.82 3.66 3.79 3.77 3.76 3.99 3.65 3.65 3.61 8.15 8.08 7.9 7.94 7.94 7.89 7.88 7.92 7.8 7.85 7.68 7.59 5.82 6.26 5.9 7.2 7.44 7.5 7.5 7.5 4.33 4.07 2.75 3.96 3.44 5.12 6.41 5.98 5.81 5.99 3.45 3.33 2.4 3.14 2.85 3.88 5.6 4.87 4.7 4.95 9.01 7.02 4.76 5.08 4.95 5.89 7.7 5.5 5.69 6.18 7.14 6.93 6.3 5.95 5.77 5.45 5.7 5.94 5.93 5.93 Average Well E-1 6.82Well E-2 3.32Well E-3 7.61 Well E-4 6.43 Well E-5 4.75 Well E-6 3.83 Well E-7 6.27 Well E-8 5.22 Jan 6, 2003 Feb 1, 2003 Feb 24, 2003 April 3, 2003 May 5, 2003 June 2, 2003 July 1, 2003 July 28, 2003 Aug 28, 2003 Sep 25, 20037.12 7.1 7.08 7.05 7.04 7.02 7.02 7.03 7.01 7 3.45 3.45 3.45 3.45 3.5 3.39 3.42 3.47 3.47 3.45 7.7 7.74 7.68 7.6 7.64 7.55 6.02 6.42 6.23 6.02 2.57 4.68 2.21 1.33 4.06 3.8 3.89 5.45 5.28 5.14 2.05 3.2 2.49 1.42 2.62 2.82 2.45 4.02 3.89 3.74 4.34 5.07 4.85 3.41 4.5 4.5 4.5 5.65 5.5 7.14 5.3 5.12 4.98 4.68 4.46 4.55 4.4 4.35 4.3 4.4 Average Well E-1 6.82Well E-2 3.32Well E-3 7.61Well E-4 6.43Well E-5 4.75Well E-6 3.83Well E-7 6.27Well E-8 5.22 Dec 2, 2003 Aug 9, 2004 Sep 2, 2004 Oct 6, 2004 Nov 5, 2004 Nov 30, 2004 Jan 13, 2005 Mar 15, 2005 Apr 13, 2005 May 11, 20056.92 6.3 6.8 6.8 6.8 6.8 6.3 6.8 6.6 6.73.35 3.15 3.15 3.15 3.05 2.95 2.35 2.85 2.65 2.65 4.23 4.7 6.7 4.8 3.1 4.7 4.2 4.9 4.3 4.5 3.17 4.6 5.6 4.35 2.8 3.6 3.2 3.5 3.1 3.8 6.61 7.2 7.85 5.6 6.5 5.6 5 3.6 3.3 44.76 6.25 4.3 4.55 4.45 4.05 3.45 3.65 3.55 4.15 Average Well E-1 6.82 Well E-2 3.32 Well E-3 7.61 Well E-4 6.43 Well E-5 4.75 Well E-6 3.83 Well E-7 6.27 Well E-8 5.22 Jun 9, 2005 Jul 13, 2005 Aug 17, 2005 Sep 21, 2005 Oct 19, 2005 Dec 7, 2005 Dec 28, 2005 Jan 25, 2006 Mar 1, 2006 Apr 6, 2006 6.6 6.6 6.6 6.7 6.7 6.5 6.6 6.4 6.5 6.4 2.55 2.35 2.55 2.45 2.35 2.35 2.35 2.25 2.25 2.15 4.7 5.8 6.2 6.3 6.7 5 4.9 4.7 4.9 5.2 3.4 5.2 5.6 5.8 6.4 4.6 3.5 4 3.9 4.5 3.2 4.1 4.6 4.8 7.9 2.8 5.4 5.2 5.3 6 3.65 4.55 4.75 4.95 4.05 3.15 4.25 3.85 3.65 3.65 Average Well E-1 6.82 Well E-2 3.32 Well E-3 7.61 Well E-4 6.43 Well E-5 4.75 Well E-6 3.83 Well E-7 6.27 Well E-8 5.22 Apr 27, 2006 May 31, 2006 Jun 21, 2006 Jul 25, 2006 Oct 4, 2006 Nov 3, 2006 Dec 6, 2006 Dec 27, 2006 Feb 5, 2007 6.4 6.5 6.5 6.4 6.4 6.5 6.4 6.4 6.3 2.25 2.25 2.35 2.15 2.15 2.35 2.35 2.35 2.45 5.7 5.3 4.5 4.9 5.8 5.9 6 6.2 6.2 5.1 4.5 4.1 4.1 5.6 5.8 6.3 5.7 5.9 7.2 6.3 5.9 5.9 4.4 9 9.1 8.1 8.3 3.75 3.75 3.75 3.55 7.95 4.35 4.55 4.65 4.55 %2 %2 %2 %2 %2 %2 %2 %2 BAXTER ROADSANKATY ROADE-7 E-8 E-6 E-5 E-2 E-1 E-3 E-4 8586 87 97 73 90 83 92 82 81 79 93 91 84 77 75 3 80 96 76 78 98 94 82A 100 Figure 1Monitoring Well Locations and MassDEP Wetlands Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA G:\Projects\Lighthouse\2014\installed_drainage_wells_20070205.mxd Data Source: Office of Geographic Information (MassGIS), Commonwealth of Massachusetts, Information Technology DivisionLEGEND Basemap: 2013 Aerial Imagery, Col-East, Inc.°0 75 150 Feet1 inch = 150 feetScale1:1,800 Parcel Boundary %2 Monitoring Well Location MassDEP Data (January 2009) Hydrologic Connection Wetland Nantucket GIS Data (2002) Pond Wetland Drainage Wells Installed as of February 2007 Approved Not Installed (Utility Obstructions) !Original Auger Hole (September 2001) Attachment G Baxter Road Geotube Project – Coastal Bank Retreat Calculations Page 1 M E M O R A N D U M Date: November 1, 2013 To: Kara Buzanoski, Nantucket DPW From: Maria Hartnett, Epsilon Associates Subject: Baxter Road Geotube Project – Coastal Bank Retreat Calculations The following memo summarizes information about the ‘Sconset bluff volume contribution calculation, including (1) a comparison of the current proposed sand mitigation volume with past Sconset Beach Preservation Fund (SBPF) proposals; (2) details on how the bank retreat rate and associated volume were calculated, including data tables; (3) comparison of the calculated bank retreat rates with shoreline change rates; (4) comparison of the calculated bank contribution volume with bank survey data; (5) a discussion of CZM’s sand volume mitigation recommendations for the Project area; and (6) a discussion of Coastal Planning & Engineering’s littoral budget prepared for the previously-proposed beach nourishment project. The Town of Nantucket requested that I prepare this memo due to my long history of calculating the bank retreat rates and associated volumes. 1.0 Comparison with Bank Retreat Rates and Volumes in Previous Submittals The following table (Table 1) summarizes the bank retreat rates and volumes provided by SBPF during project filings for the marine mattress and gabion projects, the revetment, and the geotube project. There is significant spatial and temporal variation in coastal bank retreat rates along the ‘Sconset bluff. Retreat rates are calculated along multiple transects for each lot; therefore, different project areas will have different retreat rates and associated volumes. The table below shows that each of the SBPF filings has involved a different project area. Variations in the sand mitigation volume proposed by SBPF are also a result of the varying nature of bluff erosion over time. Erosion of the bluff is an ongoing process and SBPF has periodically undertaken additional LIDAR surveys of the project site; therefore, more recent data (2013 LIDAR survey) were available for use for the geotube and revetment project than for the gabion project (2010 LIDAR survey). Similarly, the geotube and revetment project areas include project areas farther to the north, where bank retreat was occurring as far back as 1994, and therefore a more long-term bank retreat rate could be determined for the geotube and revetment projects (bank retreat rates from 1994-2013 and 2003-2013 could Page 2 be determined for the geotube and revetment projects vs. a 2003-2010 bank retreat rate for the gabion project). For the geotube project, the Town intends to follow the state standard of “Best Available Measure,” which has been consistently required by DEP, CZM, and many local Conservation Commissions. The state standard of “Best Available Measure1” for sand mitigation is to provide to the littoral system, on an annual basis, the average amount of sand that would have been provided by the eroding bank absent the project. For the marine mattress and gabion project, SBPF offered an additional component of sand mitigation (~7 cy/lf to replicate the amount of sand eroded from the nearshore); this extra component was only associated with that pilot project (which was never implemented) and is not relevant for the current project. Table I. Summary of Sand Mitigation Volumes in SBPF Proposals Project Project Area Years Used in Calculation Retreat Rate (ft/yr) Volume (cy/lf) Geotube (Current Town Application) 85-107A Baxter 1994-2013 (91-107A Baxter) 2003-2013 (85-91 Baxter) 4.6 14.3 Revetment 63-119 Baxter 1994-2013 (91-119 Baxter) 2003-2013 (71-91 Baxter) 3.8 12.0 Gabion 77-85 Baxter (North) 63-67 Baxter (South) 2003-2010 (North) 2001-2011 (South) 4.96 (North) 3.62 (South) North 11.6* (Bank) 6.8 (Nearshore) 20** TOTAL South 7.5* (Bank) 7.2 (Nearshore) 16** TOTAL *Excludes 13% fines **Includes overfill allowance 2.0 Description of Methodology The coastal bank retreat calculation was developed using the 2013 LIDAR data and high- resolution georeferenced aerial photographs dating back to 1994 to establish a long-term bank retreat average. 1 Best Available Measure(s) is defined in 310 CMR 10.04 as “… the most up‐to‐date technology or the best  designs, measures or engineering practices that have been developed and that are commercially  available.  Page 3  Bank Retreat Rate. The top of the coastal bank was digitized for 1994, 2003, and 2013 using ESRI ArcGIS software to produce the attached figure (see Figure 1). Top of coastal bank retreat was analyzed along shore-perpendicular transects spaced approximately every 20 feet. o For the portions of the geotube project area from 91-107A Baxter Road, the top of coastal bank was actively retreating as early as 1994. For these lots, a long-term (1994-2013) coastal bank retreat rate of 4.0 feet/yr was calculated. This was calculated by taking the average of the coastal bank retreat along each transect within the area from 91-107A Baxter Road (see Table 1). o For the portions of the project area from 85-91 Baxter Road, the top of coastal bank was not actively retreating in 1994 (Figure 1 shows that the 1994 and 2003 top of bank lines are coincident south of the southern half of 91 Baxter Road). For these lots, a 10-year (2003-2013) bank retreat rate of 5.8 feet/yr was calculated. This was calculated by taking the average of the coastal bank retreat along each transect within the area from 85-91 Baxter Road (see Table 1). o For the entire Project area, a single average coastal bank retreat rate was calculated by averaging the above two rates. The average is distance- weighted by transect, which reflects the fact that the majority of the geotube project area has a long-term erosion rate of 4.0 feet/yr, with only the southern 30% exhibiting the higher erosion rate of 5.8 feet/yr. The distance- weighted average is 4.6 ft/yr (see Table 2).  Volume Calculation: Section views from each of the Project lots from 85-107A Baxter Road were developed from the 2013 LIDAR survey. The volume associated with a bank retreat of 4.6 ft/yr was then determined for each lot using AutoCAD (see typical Figure 2, which shows how the cross-sectional area and associated volume were calculated for each lot). A distance-weighted average volume for all the project lots was then determined (see Table 3), yielding 14.3 cubic yards/linear foot/year (cy/lf/yr). 3.0 Corroboration of Methodology by Survey Data The bank retreat volume contribution methodology, based on LIDAR data and aerial photography, was corroborated by independent calculations performed by Woods Hole Group (WHG). WHG has top and toe of bank survey data available at profiles 90 (near 69/71 Baxter Road), 90.5 (near 79/81 Baxter Road), and 91 (near 91 Baxter Road), in years 2006, 2008, and 2013. While these data are too limited to use for the geotube project area since they do not extend far enough northward, they provide a useful check of the above methodology. WHG utilized the top and toe of bluff survey data to calculate a bank contribution volume of 12.4 cy/lf for the area covered by the profiles (69/71 Baxter Road – Page 4 91 Baxter Road); see Tables 4a and 4b. When the above methodology as described in Section 2 was applied to the same project area (71-91 Baxter Road, for years 2003-2013), the volume calculated was 13.2 cy/lf. The high degree of similarity between these two numbers (they are within 10% of one another) suggests that the methodology used by Epsilon provides an accurate representation of the bank contribution volume, and may even slightly over-estimate the bank contribution volume. 4.0 Corroboration of Methodology by Shoreline Change Data This calculation was also corroborated by shoreline change data. The WHG shoreline change data for the area from 91-107A Baxter Road were compared to the calculated bank retreat rate for 91-107A Baxter Road. The complete March 2013 WHG Shoreline Monitoring Report is included as Attachment A.  Epsilon Methodology: the 1994-2013 bank retreat rate from 91-107A Baxter Road was calculated as 4.0 ft/yr.  Shoreline Data: the 1994-2013 distance-weighted shoreline change rate for those profiles located nearest to 91-107A Baxter Road (profiles 91, 91.5, and 92) is 3.9 ft/yr. (See Table 5.) The high similarity between these two numbers again supports the accuracy of the calculated bank retreat rate, and suggests that the above methodology may also be slightly conservative. Comparisons between 1994-2013 shoreline change rates and bank retreat rates were not made for areas farther south of 91 Baxter Road, since the coastal bank was not actively retreating throughout this time period. 5.0 Discussion of CZM Recommendations Ms. Rebecca Haney of CZM provided a recommended sand volume to the Conservation Commission in a letter dated August 26, 2013 for the revetment project. As noted in SBPF’s submission to the Conservation Commission on September 6, 2013, Ms. Haney’s suggestion to utilize short-term shoreline change rates from 1978-2009 to estimate the volume of sediment eroded from the coastal bank fails to consider the coastal setting at Sconset and, by doing so, recommends the use of irrelevant data. The Sconset shoreline and beyond (from the Sewer Beds at the south to Wauwinet at the north) have been carefully monitored on a quarterly or semi-annual basis for nearly twenty years, yielding an impressive record of highly-accurate data. This monitoring has consistently shown that shoreline erosion rates in areas where the coastal bank is fronted by dunes are significantly higher than shoreline rates in areas with an eroding coastal bank. (This observation is as expected, since an eroding dune contributes less to the littoral system than an eroding bank.) In other words, survey data show that the shoreline change rates in areas fronted by Page 5 dunes are not representative of the coastal bank retreat rate. Rather, the shoreline change rate and coastal bank retreat rate may only begin to approximate one another after the coastal dune and any vegetated portion of the coastal bank have completely eroded and sufficient time has passed for an equilibrium to be reached. The coastal dune in the Project area was still present during much of the 1978-2009 time period; therefore, Ms. Haney’s suggestion to use a 1978-2009 shoreline change rate to approximate coastal bank retreat is untenable. Ms. Haney quotes a shoreline change rate of 6 to 10 feet/yr from 1978-2009 in the "project area," but this analysis apparently overlooks the northern section of the revetment project area. The CZM shoreline change data for the Project area (63-119 Baxter Road; CZM transects 285 through 306) indicates somewhat lower shoreline change rates, in the range of 4 to 9.7 feet/yr, and even these rates are in applicable given that they reflect dune erosion, not bank erosion, in the earlier years. Additionally, the CZM data is subject to uncertainty; such uncertainty is inherent to the methodology of identifying a shoreline from aerial photographs used for the broad-reaching CZM shoreline change data project. Although CZM quantifies this uncertainty for each transect; Ms. Haney fails to acknowledge this uncertainty, even though the average uncertainty for the transects in the Project area is almost 3 feet. Ultimately, Ms. Haney’s analysis does not consider the coastal setting at Sconset and therefore in our opinion does not provide an accurate representation for this project. 6.0 Discussion of the 2005 CP&E Sediment Budget During the permitting effort for the beach nourishment project, Coastal Planning & Engineering (CP&E) prepared a littoral budget based upon data from 1995-2005. (See FEIR, Sconset Beach Nourishment Project, November 30. 2006. Attachment A, Coastal Planning and Engineering (CPE) Engineering Design Report, Sconset Beach Nourishment Project, Nantucket, Massachusetts. Section 8.0, “Littoral Budget” is included as Attachment B to this memo.) This sediment budget relied upon several assumptions (such as locating the nodal point at the area of greatest erosion, applying the shoreline change rate to entire coastal profile [including eroding coastal bank], determining the volume associated with each profile by multiplying the active profile height times the shoreline recession rate and effective distance between profiles) that are appropriate for use in designing a beach nourishment project, but that may not be as appropriate for quantifying the volume and direction of sediment transport in the project area for the purposes of designing a sand mitigation program. While we feel that the CP&E analysis for the beach nourishment project has limitations when applied to the geotube or revetment project, we nonetheless reviewed their analysis to serve as another check of the proposed sediment mitigation volume. Table 6 presents the CP&E sediment budget values for those profiles within the geotube Project area (profiles 91, 92, and 92.5). The table has been updated from the original CP&E Page 6 analysis in three places: (1) the shoreline change rates have been updated to reflect the most current conditions, based on the results of the March 2013 shoreline survey; (2) the active profile height has been changed to reflect the height of the eroding bank, rather than the entire coastal profile out to the depth of closure, to reflect the geotube project’s commitment to mitigate the amount of sand eroded from the coastal bank; (3) the discount of the silt percentage applied by CP&E has been removed. This analysis yields an estimated bank contribution volume of 11.4 cy/lf (see Table 6). This volume is lower than the proposed volume of 14.3 cy/lf, again indicating that the sand mitigation volume proposed for the geotube project is adequate and possibly conservative (i.e., it may slightly overestimate the bank contribution volume). BAXTER ROAD SAN K A T Y R O A D 85 99 97 87 101 83 105 109 93 91 107 81 107A 113 Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP,swisstopo, and the GIS User Community G:\Projects\Lighthouse\2013\ConCom\Retreat\Revised\Detailed_Analysis_v2\1994-2003-2013.mxd Baxter Road Nantucket, MA Figure 1 1994-2013 Average Retreat for Lots 91-107A = . Feet/Year2003-2013 Average Retreat for Lots 85-91 = 5. Feet/Year Overall Average Retreat for Lots 85-107A = 4.6 Feet/Year Average Coastal Bank Retreat Summary Coastal Bank Retreat LEGEND Basemap: 2013 Aerial Imagery, Col-East, Inc. 1994 Top of Coastal Bank 2003 Top of Coastal Bank 2013 Top of Coastal Bank Parcel Boundary °0 60 12030Feet1 inch = 120 feetScale 1:1,440 Figure 2 Coastal Bank Sediment Contribution – Representative Profile (85 Baxter Road) Baxter Road Nantucket, Massachusetts Retreat = 4.6 ft/yr Average = 14.3 cy/lf Table 2. Top of Coastal Bank Retreat Rate Data for 85-107A Baxter Road (1994-2013) Retreat (ft) Rate (ft/yr) Retreat (ft) Rate (ft/yr) 30 107A 46.2 2.4 31 107A 43.9 2.3 32 107A 47.5 2.5 33 107 51.1 2.7 34 107 56.2 3.0 35 107 53.8 2.8 36 107 57.7 3.0 37 107 57.3 3.0 38 105 50.2 2.6 39 105 50.0 2.6 40 105 58.5 3.1 41 105 82.3 4.3 42 105 84.0 4.4 43 105 79.8 4.2 44 105 77.4 4.1 45 105 75.9 4.0 46 105 74.7 3.9 47 101 79.4 4.2 48 101 76.8 4.0 49 101 77.3 4.1 50 101 73.7 3.9 51 101 75.1 4.0 52 101 76.3 4.0 53 101 78.8 4.1 54 101 77.5 4.1 55 101 67.8 3.6 56 Public Access 74.5 3.9 57 99 70.2 3.7 58 99 68.1 3.6 59 99 75.7 4.0 60 99 80.4 4.2 61 99 75.1 4.0 62 99 77.3 4.1 63 99 84.0 4.4 64 99 85.5 4.5 65 99 85.9 4.5 66 97 81.0 4.3 67 97 77.2 4.1 68 97 84.7 4.5 69 97 91.4 4.8 70 97 99.2 5.2 71 97 99.0 5.2 72 97 100.4 5.3 73 97 98.1 5.2 74 93 85.6 4.5 75 93 95.4 5.0 76 93 98.8 5.2 77 93 104.5 5.5 78 93 108.2 5.7 79 91 97.7 5.1 80 91 71.1 3.7 1994-2013 2003-2013 (ft)Transect Lot Page 1 of 2 Retreat (ft) Rate (ft/yr) Retreat (ft) Rate (ft/yr) 1994-2013 2003-2013 (ft)Transect Lot 81 91 31.9 3.2 82 91 20.5 2.1 83 87 13.2 1.3 84 87 22.8 2.3 85 87 55.1 5.5 86 87 76.8 7.7 87 87 84.5 8.5 88 87 81.1 8.1 89 87 61.6 6.2 90 87 48.3 4.8 91 85 67.7 6.8 92 85 67.4 6.7 93 85 61.0 6.1 94 85 60.6 6.1 95 85 54.9 5.5 96 85 59.1 5.9 97 85 66.8 6.7 98 85 72.3 7.2 99 85 67.3 6.7 100 85 67.2 6.7 101 85 67.9 6.8 102 85 64.3 6.4 103 85 64.5 6.5 Average Bank Retreat Rate by Section 4.0 5.8 Distance weight (#transects/total transects) 0.7 0.3 Average Bank Retreat Rate 85-107A 4.6 Page 2 of 2 Table 3. Coastal Bank Contribution Volume for 85-107A Baxter Road Lot Retreat Rate ft/yr Section Volume cy Lot Length1 ft Weight (Lot Length/Total Project Length) Volume*Weight cy 107A 4.6 17.2 71 0.05 0.8 107 4.6 16.9 100 0.06 1.1 105 4.6 16.0 175 0.11 1.8 101 4.6 14.7 200 0.13 1.9 99 4.6 13.9 185 0.12 1.6 97 4.6 13.6 180 0.11 1.6 93 4.6 13.3 98 0.06 0.8 91 4.6 13.3 94 0.06 0.8 87 4.6 13.5 177 0.11 1.5 85 4.6 13.3 294 0.19 2.5 Total Project Length1(ft)1574 14.3 1. Length measured along the +26 MLW contour. Average Bank Contribution Volume (cy) Table 4a. WHG Sconset Bluff and Shoreline Change Data for Profiles 90, 90.6, and 91 (2006, 2008, 2013)D (ft) Z (ft, MLW) D (ft) Z (ft, MLW) D (ft) Z (ft, MLW)2006 34.6 0 -144.19 73.1 -68.59 11.72008 43.3 0 -154.89 72.31 -76.8 12.232013 50.3 0 -161.5 74.04 -75.5 9.412006 14.1 0 -128.49 81.9 -33.59 9.32008 29.5 0 -135.04 84.4 -27.85 8.932013 36.1 0 -167.04 84.86 -71.68 9.442006 21.8 0 -174.24 76.3 -71.65 8.42008 21.7 0 -174.1 76.3 -77.34 10.62013 26.2 0 -197.52 76.72 -113.61 9.64D is distance along baseline relative to 0 at benchmarkZ is elevation relative to MLW 1992Table 4E. WHG Sconset Bluff Volume Change Data for Profiles 90, 90.6, and 91 (2006-2013)ProfileDistanceftDistance Weight2006-2013 Bank Contribution Volume1cy90 425 0.254.590.6 639 0.38 17.691 622 0.37 12.4Weighted Bluff Retreat Volume12.41. Determined by calculating that volume associated with the difference in bluff positions from 2006 to 2013.Profile 90.6Profile 9169/71 Baxter Road79/81 Baxter Road91 Baxter RoadTop of Bluff Toe of BluffShoreline (0-MLW ft)Approximate LocationYearProfile 90 Table 5. Shoreline Change Rates from November 1994 to March 20131Profile Approximate LocationEffective Distance2ftWeight(Effective Distance  Total Distance)Shoreline Change Per Profile1 (Nov 1994-Mar2013)ftAverage Annual Shoreline Change ft(Shoreline Change/ 18.4 years)91 91 Baxter6220.43 -96.5-5.291.599/101 Baxter4310.30 -58.9-3.292 105 Baxter4040.28 -45.4-2.51457Weighted average 85-107A Baxter Road-3.91. From Southeast Nantucket Beach Monitoring, March 2013, 60th Survey Report, prepared by Woods Hole Group, August 2013.2. From FEIR, Sconset Beach Nourishment Project, November 30. 2006. Attachment A, Coastal Planning and Engineering (CP&E) Engineering Design Report, Sconset Beach Nourishment Project, Nantucket, Massachusetts.Total Distance (ft) Table 6. Update of Coastal Planning & Engineering 1995-2005 Littoral Budget Analysis Profile Approximate LocationEffective Distance2ftShoreline Change Per Profile1 (Nov 1994-Mar2013)ftAverage Annual Shoreline Change ft(Shoreline Change/ 18.4 years)Top of Bank Height2 ft, MLWToe of Bankft, MLWActive Profile HeightftVolume3 (cy)91 91 Baxter 622 -96.5 -5.2 82 8 74 -894191.5 99/101 Baxter 431 -58.9 -3.2 90 8 82 -419092 105 Baxter 404 -45.4 -2.5 102 8 94 -3470Total Volume Eroded from Project Area (CY)-16601Total Volume Eroded from Project Area (CY/LF)-11.41. From Southeast Nantucket Beach Monitoring, March 2013, 60th Survey Report, prepared by Woods Hole Group, August 2013.2. From FEIR, Sconset Beach Nourishment Project, November 30. 2006. Attachment A, Coastal Planning and Engineering (CP&E) Engineering Design Report, Sconset Beach Nourishment Project, Nantucket, Massachusetts.3. Volume determined by multiplying the effective distance * active profile height * average annual shoreline change, then dividing by 27 to convert to cy (per Section 8.0 of CP&E report referenced above in #2). Attachment H Bank Swallow Survey Results and Habitat Requirements (dated July 3, 2017) Robert S. Kennedy, Ph.D. Ornithologist, Consultant 18 Riverview Road Durham, NH 03824 osprey02554@yahoo.com 508-577-4105 3 July 2017 Mr. Andrew Bennett, Chair Nantucket Conservation Commission 2 Bathing Beach Road Nantucket, MA 02554 Subject: Bank Swallow (Riparia riparia) Survey Results and Habitat Requirements along the Coastal Bank of Nantucket from Hoicks Hollow Road to 85 Baxter Road. Reference: Bank Swallow nesting habitat along the coastal bank at 93 Baxter Road, Nantucket, MA Bank Swallows on Nantucket along the Sankaty Coast: Bank Swallows are fairly common on Nantucket where they are known to nest in small colonies with individual burrows dug into vertical sand and clay banks along the north, east, and south coasts, and along Nantucket Harbor, particularly at the UMass Field Station. The Massachusetts Breeding Bird Atlas 2 prepared and maintained by the Massachusetts Audubon Society (Mass Audubon) considers their population stable to increasing on Nantucket. They are not listed as Endangered, Threatened or of Special Concern by the Massachusetts Division of Fisheries and Wildlife. From 2005 to 2009, I conducted over 95 surveys of the birds along the east coast of Nantucket from Hoicks Hollow Road to Siasconset from early April through late August each year. I observed Bank Swallows during 44 of those surveys between mid-May to mid-August with numbers ranging from 1 to 30 birds per survey. I also surveyed Bank Swallows nesting cavities in the coastal bank along the same route on 16 December 2010. Although Bank Swallows had finished nesting and migrated long before the survey, 41 nest cavities were still present. Table 1 provides a summary of the number and location of the nest cavities in 2010 while Figure 1 shows a Google Earth image of their distribution. In the Sankaty Coastal Bank, Bank Swallows only nested 1) where there existed a vertical cliff face of about 5 feet or higher below the top of the coastal bank, 2) within 2 to 4 feet from the top of the coastal bank, 3) where the cliff substrate permitted excavation by the swallows without that substrate collapsing on them, and 4) where the top of the coastal bank is about 25 feet or higher from the active beach. Table 1. Bank Swallow Nest Holes on Sankaty Coastal Bank - 16 December 2010 Field Work Conducted by Dr. Bob Kennedy No. of Swallow Address Map Plot Owner Nesting Cavities Latitude* Longitude* 73 Baxter Road 49-27 Henrickson 6 41 16' 34.5" 069 57' 40.4" 75 Baxter Road 49-30 Osborn 8 41 16' 35.9" 069 57' 40.9" 79 Baxter Road 49-32 Weymar 1 41 16' 38.1" 069 57' 41.0" 99 Baxter Road 48-18 Furrow 1 41 16' 48.2" 069 57' 45.2" Location 3 7 41 16' 55.5" 069 57' 48.4" Location 2 4 41 16' 56.1" 069 57' 48.8" Location 1 14 41 17' 17.4" 069 58' 01.0" Total Nest Cavities 41 *Coordinates were taken from the beach below the nest cavities Figure 1. Google Earth image showing the locations of Bank Swallow nest cavities listed in Table 1. June 2017 Bank Swallow Survey: On 20 June 2017, I conducted another survey of Bank Swallows both individual birds and nest cavities from Hoicks Hollow to the beach location of 85 Baxter Road, a distance of about 0.93 miles. I identified approximately 100 nest cavities, and saw about 30 individual birds, some coming and going from active nest cavities. Although many of the nest cavities were either individual holes or a few holes spaced along the coastal bank, I found two locations where nest cavities were concentrated. Interestingly, both locations were the same places I identified small colonies in December 2010 – Location 1 in 2017 comprised about 25 nest cavities and Location 2-3 contained about 35 nest cavities. Figure 2 provides a view of the Location 2-3 nesting colony during the 20 June survey. This colonies lies between 115 & 109 Baxter Road Figure 2. Bank Swallow nesting colony between 115 & 109 Baxter Road. During the June 2017 survey, I identified stretches of unsuitable nesting habitat along the coastal bank ranging from about 100 feet to over 700 feet. The angle of repose of eroded material in these areas extended from the active beach to the top of the coastal bank, or within a few feet of the coastal bank and did not contain suitable vertical cliff space for nesting swallows. Evaluation of the Bank Swallow nesting habitat at or near 93 Baxter Road: The coastal bank along the property of 93 Baxter, in the past (December 2010) and at present, does not have any nest cavities of Bank Swallows. The property does not contain suitable nesting habitat, i.e. a vertical cliff face of about 5 feet or higher below the top of the coastal bank. In fact, the lack of suitable habitat, and nest cavities, extends approximately 200 feet to the north of, and 300 feet to the south of 93 Baxter Road. Figure 3 portrays a strip of coastal bank and the broad line defines the area about 650 feet long that in my view does not contain suitable habitat for nesting Bank Swallows. Figure 4 is the coastal bank immediately north of 93 Baxter Road and Figure 5 is the coastal bank immediately south of 93 Baxter Road. It is clear from these photos that there is no vertical exposed cliff of 5 feet or greater below the top of the coastal bank and that the angle of repose of the bank now covered with American Beach Grass extends to the top or very close to the top of the bank. Figure 3. Broad line delimits unsuitable nesting habitat for Bank Swallows. Figure 4. Coastal bank immediately north of 93 Baxter Road. Figure 5. Coastal bank immediately south of 93 Baxter Road. Attachment I Sconset Bluff Erosion Control Alternatives and Recommendations (dated July 2013) SCONSET BLUFF EROSION CONTROL ALTERNATIVES and RECOMMENDATIONS 21597/Sconset i Erosion Control Recommendations for Sconset TABLE OF CONTENTS EXECUTIVE SUMMARY 1 EROSION CONTROL ALTERNATIVES AND RECOMMENDATIONS FOR SCONSET 3 1.0 Current Status of Baxter Road and Adjacent Homes 3 2.0 Alternatives for Road and Bluff Protection 6 2.1 Geotextile Tubes 6 2.2 Beach Nourishment 6 2.3 Dewatering 7 2.4 Breakwater 7 2.5 Groin 8 2.6 Seawall 8 2.7 Drift Fence 9 2.8 Coastal Bank Terraces 9 2.9 Marine Mattress and Gabion System 10 2.10 Revetment 11 3.0 Recommended Action and Conclusions 12 3.1 Recommended Action - Revetment 12 3.1.1 Description of Revetment Design 12 3.1.2 Environmental Considerations 12 3.1.3 Regulatory Considerations 13 3.1.4 Cost 14 3.1.5 Construction Information 14 3.1.6 Assessment of Effectiveness 14 3.2 Public Benefits 14 3.3 Obtaining Environmental Approval for Recommended Action 15 3.3.1 Emergency Project Approval 15 3.3.2 Normal (Non-Emergency) Project Approval 16 3.4 Conclusions 17 ATTACHMENT A - FIGURES AND PLAN Figure 1 Aerial Locus Map Figure 2 Current Setback of Road and Houses to Top of Bank, 93 to 105 Baxter Road Figure 3 Current Setback of Houses to Top of Bank, 69 to 83 Baxter Road Figure 4 Current Setback of Houses to Top of Bank, 109 to 115 Baxter Road Typical Revetment Section 21597/Sconset ii Erosion Control Recommendations for Sconset ATTACHMENT B REVETMENT EXAMPLES Figure B-1 Hull, Point Atherton Revetment Figure B-2 Hull, Green Hill Revetment Figure B-3 Scituate, Fourth Cliff Revetment Figure B-4 Plymouth, Gurnet Revetment Figure B-5 Plymouth, Cedarville Landing Revetments Figure B-6 Nantucket, Capaum Pond Road Revetment Figure B-7 Nantucket, Westcliff Lane Revetment 21597/Sconset 1 Erosion Control Recommendations for Sconset EXECUTIVE SUMMARY Immediate protection of Baxter Road is critical for the 551-foot stretch from 99-105 Baxter Road, where the distance between the road and the top of the coastal bank is less than 45 feet (this distance ranges from 29 to 44 feet). The coastal bank in this area eroded 20 to 30 feet or more from 2012 to 2013; such catastrophic erosion may well occur again during the coming winter storm season. Therefore, some type of protection must be in place before the start of the 2013- 2014 winter storm season or else certain sections of Baxter Road may have to be closed or may actually be breached by the erosion. Similarly, immediate protection of Baxter Road is also necessary for all remaining homes along Baxter Road from 73 Baxter to the Lighthouse, to protect both Baxter Road and threatened homes that are as close as 11-feet to the top of the coastal bank. Significantly, most of the homes from 73 Baxter Road to the Lighthouse would be lost if another severe winter storm season occurs. The opportunity for private funding of erosion control efforts will become more limited if additional homes are lost, moved, or demolished. Multiple erosion control alternatives have been considered. Sconset is a high-energy environment; therefore, some alternatives are highly unlikely to be effective, such as geotextile tubes and breakwaters. Other alternatives, such as beach dewatering and drift fences, have been tried and proven ineffective over the long term at this location. Still other alternatives, such as seawalls and beach nourishment, could be effective but would be difficult or impossible to get permitted under the Massachusetts Wetlands Protection Act (WPA) and Nantucket Wetlands Bylaw regulations, and have other negative aspects. The groin alternative would not be effective or environmentally feasible at Sconset without an accompanying beach nourishment project or significant sand mitigation program. The coastal bank terraces alternative has been implemented at Sconset for multiple years as a short-term measure, but it has been repeatedly documented that this alternative simply cannot withstand major storms and requires nearly constant post-storm maintenance, which is not always feasible in successive storm situations. A marine mattress/gabion alternative or a revetment alternative would both provide effective protection for Baxter Road and adjoining homes in a high-energy environment like Sconset. Revetments offer an advantage over the marine mattress system in that they do not require anchoring into the bank face, are composed of natural rock material, would not require removal in the event of system failure, and have a comparable or lower cost than the marine mattress/gabion alternative. Revetments are also easy to install and offer a very long service life. Revetments are therefore the recommended alternative for erosion control at Sconset. Given the high erosion rates of the coastal bank, it is critical that the revetment is installed by late fall of 2013. Meeting this schedule would likely require authorizing the revetment as an “Emergency Project” under the WPA or obtaining Conservation Commission approval for the project in a single public hearing or compressed public hearing process during the month of July. Subsequent to this approval, 4-6 weeks would be required to select a contractor; followed by 8-10 weeks for construction of a 551-linear foot revetment, or 4 months for a 1,500-linear foot 21597/Sconset 2 Erosion Control Recommendations for Sconset revetment. Provided regulatory approval is secured by July, the contractor could be selected in August, and construction could occur from mid-August or September through early December, depending on the length of revetment installed. In addition to the areas requiring immediate protection, near term (2014) protection of Baxter Road is also recommended for the remaining stretch of Baxter Road from 53 Baxter to the Lighthouse. The significant erosion occurring along Baxter Road from 2012-2013 underscores the point that this entire section is vulnerable to erosion and should be protected as soon as possible. 21597/Sconset 3 Erosion Control Recommendations for Sconset EROSION CONTROL ALTERNATIVES AND RECOMMENDATIONS FOR SCONSET 1.0 Current Status of Baxter Road and Adjacent Homes Baxter Road is a public way owned by the Town of Nantucket that provides the only access to the recently relocated Sankaty Head Lighthouse, as well as access for the public, residents, and emergency vehicles to more than 100 homes (Figure 1). Various utilities (water, sewer, communication and electric services) are also included within Baxter Road. At present, sections of Baxter Road are now within 29 to 44 feet of the edge of Sankaty Bluff (referred to herein as the “coastal bank”) (Figure 2). Similarly, several homes along Baxter Road are within 10 to 20 feet of the top of the coastal bank (Figures 3 and 4). Many of these homes have significant historical value1 and they also represent a significant financial contribution to the Town of Nantucket via taxes paid. Erosion of the coastal bank along the northern portion of Baxter Road has been apparent since 1994, and has been accelerating over the past decade. As detailed in Table 1 below (which provides information on loss of costal bank for each lot from 55 Baxter Road to 119 Baxter Road), last winter (2012-2013) was particularly severe and resulted in coastal bank retreat of 20 to 30 feet or more along most Baxter Road properties. While the 2012-2013 winter season yielded higher-than-average erosion rates, it underscores the point that chronic erosion along this portion of the coastal bank can be catastrophic and that annual coastal bank losses of 20 to 30 feet or more must be anticipated. Table 1 also presents the following information: 1. Current (May 2013) minimum setback distance between Baxter Road and the top of the bank, 2. March 2012 setback distance between Baxter Road and the top of the bank, 3. Amount of erosion of the bank last year (March 2012 to May 2013), and 4. Current (May 2013) setback distance between buildings on each lot and the top of the bank. This table makes it clear that sections of Baxter Road are within one major storm (or series of successive storms) of being undermined or lost. Likewise, several homes are within one major storm or series of successive storms of having to be moved or demolished, while many others will be threatened in the near future (See Figures 3 and 4). 1 Nantucket Preservation Trust. 2007. ‘Sconset Historic Site Survey. 21597/Sconset 4 Erosion Control Recommendations for Sconset Table 1 Baxter Road and Building Setback Distances to Top of Coastal Bank & 2012- 2013 Coastal Bank Erosion Rates for 55 to 119 Baxter Road Lot # Property Length (ft) 2013 Minimum Baxter Road Setback to Top of Bank (ft)1 2012 Baxter Road Setback to Top of Bank (ft)2 2012-2013 Loss of Coastal Bank (ft) 2013 Minimum Building Setback to Top of Bank (ft) 119 67 84 94 10 n/a 117 113 95 100 5 n/a 115 104 91 103 12 18 113 93 84 98 14 13 Way 20 96 102 6 109 163 80 101 21 11 107 162 65 92 27 n/a Way 18 65 90 25 105 166 29 60 31 n/a 101 188 37 60 23 n/a 24 99 173 44 74 30 17 97 171 61 93 32 24 Way 18 88 93 89 58 81 23 8 91 94 52 87 35 n/a 87 164 57 100 43 n/a Way 26 85 281 73 100 27 n/a 83 134 91 115 24 32 81 106 115 138 23 18 79 99 122 144 22 13 77 88 120 144 24 75 75 80 127 148 21 11 73 149 122 148 26 56 Way 30 71 102 144 167 23 67 69 109 160 n/a n/a 46 67 79 181 n/a n/a 50 Way 30 65 69 179 n/a n/a 29 63 182 164 n/a n/a 30 Way 23 61 128 162 n/a n/a 69 59 147 153 n/a n/a 60 55 119 93 n/a n/a 32 Notes: 1. 2013 distances based on field measurements taken on 5/30/13. 2. 2012 distances based on March 2012 aerial photo; distances were measured in the same location on each lot as the 2013 measurements for consistency. n/a - Top of bank retreat not yet apparent on 2012 aerial photo; erosion of lower portion of bank apparent on many properties. 21597/Sconset 5 Erosion Control Recommendations for Sconset In light of these conditions, the following recommendations are made:  Immediate protection of Baxter Road is critical for the 551-linear foot stretch from 99-105 Baxter Road, where the distance between Baxter Road and the top of the coastal bank is less than 45 feet (this distance ranges from 29 to 44 feet; see shaded area in Table 1 below and Figure 2). Bank protection must be in place before the 2013 winter storm season in order to eliminate the risk of road closure.  Immediate protection is also necessary for all remaining homes along Baxter Road from 73 Baxter to the Lighthouse, to protect both Baxter Road and threatened homes that are as close as 11-feet to the top of the coastal bank (see Figures 2-4). Most of the homes from 73 Baxter Road to the Lighthouse would be lost if another severe winter occurred. Protection of these homes likewise protects Baxter Road and its associated utilities. Further, the opportunity for private funding of erosion control efforts will become more limited if additional homes are lost, moved, or demolished. In addition to the areas requiring immediate protection, near term (2014) protection of Baxter Road is also recommended for the remaining stretch of Baxter Road from 53 Baxter to the Lighthouse. The significant erosion occurring along Baxter Road from 2012-2013 underscores the point that this entire section is vulnerable to erosion and should be protected as soon as possible. 21597/Sconset 6 Erosion Control Recommendations for Sconset 2.0 Alternatives for Road and Bluff Protection This section provides a summary description of ten alternatives for preventing erosion of the coastal bank at Sconset. 2.1 Geotextile Tubes Geotextile tubes (geotubes) are fabricated from high strength, woven polyester or polypropylene sewn together into a tube shape and filled with sand. A conceptual geotube design for a 50-year storm would consist of at least four 30-foot-circumference geotextile tubes installed in a terraced alignment and covered with clean sand fill. Construction would require excavating the existing profile to +4.5 feet MLW and installing a 3-foot- circumference anchor tube and scour apron. Geotubes would then be installed and filled on the excavated terraces to approximately 5 feet tall and 11 feet wide. After the geotubes were filled, a clean sand fill would be placed to a top elevation of approximately +23.5 feet MLW. The sand fill would be placed on a 1 vertical: 2.5 horizontal slope to meet existing grade while maintaining a continuous one foot thick sand cover over the filled tubes. Geotextile tubes are not well-suited to a high energy environment like Sconset. Too much scour at the toe could potentially lead to structural failure (even when a scour apron is included in the design). Geotubes are susceptible to damage from vandalism, debris, and storm waves; storm-driven debris may puncture and tear the tube. For this reason, maintenance costs for geotubes tend to be higher than for other alternatives. When ripped open by storm waves, geotextile tubes may fail in place, emptying sand onto the beach and possibly releasing geotextile material to the coastal environment. The release of sacrificial sand would not have any adverse environmental effects since clean, beach-compatible sand would be used to fill the tubes. However, replacement of the geotube would be expected to be required on a frequent basis (one or more times annually). Such replacement often cannot be accomplished between successive storms, potentially leaving the bank vulnerable to wave-induced scarping at the toe (and subsequent slumping of the upper bank, which undermines vegetative stabilization that otherwise works) at the time when protection is most needed. For these reasons, geotubes are not considered a viable long- term erosion control solution. 2.2 Beach Nourishment Beach nourishment would involve the placement of approximately 2.6 million cubic yards of sand on Sconset Beach. The nourished beach would be approximately 200 feet wide with a berm height of 12-16 feet above MLW. Sand would be obtained from an offshore borrow site; a likely candidate would be the offshore shoal system known as Bass Rip, though other potential sites could also be evaluated. The wider beach would absorb and dissipate wave energy, thereby increasing protection to infrastructure and property threatened by erosion and storm damage. Additionally, the wider beach would potentially 21597/Sconset 7 Erosion Control Recommendations for Sconset offer increased public recreation opportunities. Renourishment would be required approximately every 5 years. While the beach nourishment alternative offers significant benefits, there are potential adverse impacts that must be carefully minimized and/or mitigated. The nourishment envelope would cover more than 125 acres of beach, inter-tidal, and sub-tidal habitats. Direct mortality to the marine organisms living in or on the seafloor would be unavoidable in those areas covered by the beach nourishment sand, although these resources would be expected to recover in 1-3 years. Areas of nearshore cobble habitat important to the local fishing community would be temporarily or permanently impacted by the placement of the beach fill and would require replication of such habitat nearby. While beach nourishment could be planned and executed in a manner that protects threatened public infrastructure and homes while resulting in a minimal level of environmental impact, beach nourishment is not desirable at Sconset due to potential impacts to locally important fishery resources. Therefore, beach nourishment is not a recommended erosion control alternative. 2.3 Dewatering Beach dewatering systems are based on the supposition that draining water from the beach face can increase the percolation of swash zone water into the beach and promote the deposition of new sediment that is actively moving through the swash zone. The Sconset Beach Preservation Fund (SBPF) installed four different systems that met with mixed levels of performance success. Three of the systems, Lighthouse North (LHN), Lighthouse South (LHS), and Lighthouse South-South (LHS-S) were severely damaged and ultimately removed. The fourth system at Codfish Park is covered by the existing beach, due to beach accretion after its installation and subsequent system upgrade. Once the beach accreted to a point where the system could no longer pump effectively, operations were terminated and the beach responded by eroding. Although the patterns of shoreline erosion and accretion at Codfish Park have not been linked conclusively with operations of the dewatering system, they are evidence of the system’s potential effectiveness. However, based on the extensive storm damage documented to the LHN, LHS and LHS-S systems, and the difficulties involved in performing associated repair and maintenance, beach dewatering as a stand-alone alternative is not preferred or considered viable for long-term, effective protection of threatened public infrastructure and homes. 2.4 Breakwater Manufactured breakwaters typically consist of structures placed in water depths of 7 to 9 feet that are intended to break wave action and artificially perch the landward beach. Breakwaters could consist of reef balls, narrow-crested artificial reefs, sunken barges, or rubble mounds. Artificial reef balls and narrow-crested artificial reefs would have limited effectiveness in a high-energy environment like Sconset. Sunken barges would offer a 21597/Sconset 8 Erosion Control Recommendations for Sconset broader profile to potentially dissipate wave energy but would be subject to corrosion, settlement, and movement along the seafloor due to hydrodynamic forces. Environmental permits for sunken barges may be difficult to obtain given their likely impacts and uncertain effectiveness. An effective offshore breakwater design at Sconset would likely require a large emergent rubble-mound breakwater system, which would occupy a large area of the bottom, permanently impacting nearshore habitat. In addition, until the beach behind such a structure accreted to the point where it formed a tombolo (i.e., it accreted seaward to the structure itself), a large emergent breakwater would act as a barrier to longshore sediment transport, starving downdrift beaches. The long-term efficacy of such a structure is also questionable. Future consideration of a breakwater on an experimental basis, particularly if combined with other erosion control measures, may be warranted. At present, breakwaters are not a preferred alternative for erosion control at Sconset due to limited or questionable long-term effectiveness, potential impacts to nearshore habitat, and potential impacts to downdrift beaches. 2.5 Groin Groins are concrete, rock, and/or timber structures constructed perpendicular to the shoreline that are designed to catch and trap sand being transported downdrift. Groins compartmentalize the shoreline, minimizing sediment losses from a given section of beach which can have adverse impacts to adjacent downdrift beaches by reducing the sediment supply available to these areas. When used in conjunction with a beach nourishment project, low-profile or semi-permeable groins can reduce the rate of sediment loss from erosion hotspots within a nourished design beach profile and enhance the effectiveness of nourishment. When used on their own without sand mitigation; however, traditional coastal groins are not preferred due to downdrift impacts and consequently environmental regulatory constraints. Groins would not be effective or environmentally feasible at Sconset without an accompanying beach nourishment project or significant sand mitigation program. 2.6 Seawall A properly-designed seawall for the Project shoreline would be a massive vertical structure composed of hard, impervious material such as concrete or steel that would be placed on the coastal beach at the toe of the coastal bank. Composite seawalls could also be constructed, which might include a seawall fronted by a rubble-mound structure designed to protect the toe of the structure by dissipating wave energy during storms. A preliminary analysis of seawall designs for the Project area suggests that in order to withstand long-term erosion pressures, the structure would need to extend from 10 feet below the existing beach face to a height equal to at least 20 feet up the face of the coastal bank. 21597/Sconset 9 Erosion Control Recommendations for Sconset Seawalls are not a preferred erosion control method for Sconset primarily due to environmental regulatory constraints stemming from likely environmental effects. Since they are vertical, smooth structures, seawalls in high energy beach areas like Sconset can cause additional wave reflection and turbulence and thus maintaining a beach in front of them can be a challenge. Depending on local conditions, seawalls can decrease the supply of sediment in the littoral system. Additionally, removing a seawall of the size and depth below the beach required at Sconset in the event of negative impacts would be extremely expensive and difficult. 2.7 Drift Fence Drift fence is designed to trap wind-blown sand and is typically placed a few feet seaward of an eroding dune or coastal bank. While drift fence can cause some minor accumulation of sand, it has been shown ineffective over the long term in a high energy environment at Sconset. The SBPF installed “Duneguard” drift fence along with the beach dewatering systems over a decade ago. Sand nourishment was placed landward of the drift fence to add a layer of protection to the toe of the coastal bank. Even with this provision, however, the drift fence did not make a measureable impact on the erosion of the coastal bank over the long term. Drift fence can also be a significant source of marine debris when it fails after coastal storms. Drift fence is therefore not a suitable alternative for preventing erosion at Sconset. 2.8 Coastal Bank Terraces Coastal bank terraces of differing designs (utilizing mats or bags fashioned from coir or jute) have been utilized seaward of portions of Baxter Road since the early 2000’s. The current design has been in use since 2006, most consistently at 79 Baxter Road, and consists of jute fabric terraces 3-feet high by 5-feet deep by 50-feet long, constructed to an elevation of 12 to 13 above the back of the beach (approximately +20 to +23 MLW). The terraces are secured using duckbill ground anchors buried into the coastal bank. The current design eliminates the anchor stake and coir debris that occurred when earlier terrace installations were damaged during storms. These terraces are designed to be sacrificial. During storm events, they rip open and release sand to the beach; therefore, the terraces have to be completely replaced once or twice a year. Sand for the terraces is obtained from on-island pits and is trucked to Baxter Road, where it is dumped over the top of the bank at designated access points and then placed in the terraces using bobcat or skid steer equipment. Approximately 9-10 cubic yards of sand per linear foot of terraces have been added to the littoral system each year through the maintenance of the terraces. Nearby properties have benefited from the diffusion of sand onto their adjacent beaches. The terraces have helped to prevent erosion of the toe of the coastal bank at 79 Baxter Road; however, these terraces do not provide sufficient protection during major or successive storm events and cannot be considered a viable long-term option. The strongest storms the terraces have been subjected to have been 10-year storms, and the terraces have 21597/Sconset 10 Erosion Control Recommendations for Sconset not withstood those events. Rather, the sacrificial terraces have ripped open and released their sand as designed, subsequently requiring complete replacement multiple times a year. During major or successive storm events, wave-induced scarping can still occur at the toe of the coastal bank, followed by slumping of the upper bank, which undermines vegetative stabilization of the upper bank that otherwise works. Such slumping tears out vegetation on the upper bank and emphasizes that vegetation on the upper bank face cannot have a meaningful impact on slowing upper bank erosion without effective toe protection in place. Terraces are not a viable long-term option because they cannot protect the toe of the coastal bank during major or successive storms and require nearly constant post-storm maintenance. 2.9 Marine Mattress and Gabion System This alternative would consist of placing flexible marine mattresses and gabion baskets on the lower portion of the coastal bank face and along the toe of the coastal bank. Three rows of gabion baskets would be buried in the beach; each basket would be 4-foot high x 5-foot wide x 10-foot-long and filled with 12- to 22-inch diameter stones. Up to three rows of marine mattresses would be placed on top of the gabions along the bank face; each mattress would be 6 feet wide x 18 inches high x 16-30 feet long and filled with 3- to 6- inch diameter stones. The mattresses would extend up the bank face to an elevation of approximately +26 feet Mean Low Water (MLW), in order to provide protection from a 100-year storm. Both the mattresses and the gabions would be formed from HDPE geogrid material. Returns would be placed at the ends of the system to prevent end scour. The marine mattresses and returns would be anchored to the existing bank slope using Platipus ground anchors or helical anchors driven about 12 feet deep into the coastal bank under the mattresses. Finally, a sand cover would be placed over the entire installation and the upper portion of the bank would be planted with native vegetation to provide habitat and decrease erosion of the upper bank. Marine mattresses and gabions have been used effectively in multiple locations throughout Massachusetts (Boston, Plymouth, Martha’s Vineyard, and at Hinckley Lane on Nantucket) and also at Cape May, New Jersey. Experience at these locations has shown that properly- designed marine mattress and gabion systems can be effective in high-energy environments like Sconset. Including a sediment cover in the design may prevent potential impacts to adjacent beaches. The sloped and porous nature of the system would minimize wave reflection and encourage energy dissipation. Disadvantages associated with the system are that the geogrid material must be removed if the system fails, the relatively high cost of this alternative, and the (inaccurate) perception that the required anchors may serve to destabilize the coastal bank. This perception is part of why a marine mattress and gabion project at Sconset was not permitted by the Conservation Commission in 2012. For these reasons, marine mattresses and gabions are not a preferred alternative. 21597/Sconset 11 Erosion Control Recommendations for Sconset 2.10 Revetment A revetment is a coastal engineering structure consisting of rock facing to protect a sloping embankment against erosion. Revetments generally consist of an outer protective layer of large rocks (approximately 3-6 feet in diameter), an inner core layer of smaller rocks, and toe protection. The outer protective layer provides the basic protection against wave action, while the inner core layer acts as a filter layer to assure drainage and retention of the underlying soil. The toe protection is needed to provide stability against undermining at the bottom of the structure. The primary advantage of a revetment is its flexibility, which allows it to settle into the underlying soil or experience minor damage and still retain its ability to protect the bank from erosion. Revetments also have rough surfaces, which reduce wave runup and overtopping. Like other coastal engineering structures placed in front of or on the face of a coastal bank to provide storm damage prevention, revetments can potentially interrupt the supply of sediment to the littoral system; therefore, monitoring of adjacent beaches and/or some type of initial or annual sand mitigation would be required. Additionally, like other coastal engineering structures, scour may potentially occur at the either end of the structure from wave reflection. The most suitable end treatment when there are adjacent eroding banks is to taper the ends of the structure using smaller stone to help blend the structure into the adjacent, unprotected bank. Revetments are a common coastal structure used for erosion control and have been proven effective in environments similar to Sconset (see Section 3.1.6 below and Attachment B). Revetments are relatively easy to install and maintain, with very long service lives. Additionally, the cost of revetment installation is comparable to or less than other alternatives considered and maintenance costs tend to be lower. Revetments also consist of natural rock material and do not require removal in the event of system failure. For these reasons, a revetment is considered the preferred alternative for preventing further erosion of the coastal bank, thereby protecting Baxter Road and the homes along it. 21597/Sconset 12 Erosion Control Recommendations for Sconset 3.0 Recommended Action and Conclusions 3.1 Recommended Action - Revetment The recommended action to protect Baxter Road, its associated infrastructure, and private homes along Baxter Road is a revetment. Revetments are proven effective in high-energy environments such as Sconset, are easy to install and maintain, are composed of natural rock material, are not anticipated to result in adverse environmental impacts, and offer a cost of installation and maintenance that is comparable to or less than other alternatives. Given the high-energy wave environment at Sconset, “softer” solutions simply cannot be effective long-term against major storms. Details of the revetment installation are provided below. 3.1.1 Description of Revetment Design In Sconset, a rock revetment could be placed on the lower slope of the coastal bank from Elevation +0.0 MLW to Elevation +26 MLW to provide protection against wave action from a 100-year design storm. The revetment would consist of a geotextile fabric lining the coastal bank, a filter layer of 4-inch to 8-inch diameter crushed stone, and two layers of larger “armor” stone (see accompanying sheet for size gradation). The armor layer would provide the basic protection against wave action, while the filter layer assures drainage and retention of the underlying soil. The revetment would likely be graded to a maximum slope of 1 foot vertical to 1.5 feet horizontal (see accompanying sheet in Attachment A). During installation of such a revetment, a layer of geotextile filter fabric would first be placed on the bank face. Next, a minimum 18-inch thick filter layer consisting of 4-inch to 8-inch diameter crushed stone would placed. Two layers of armor stone would be placed on top of the filter layer to form a thickness of 6-feet (when measured perpendicular to the face of the coastal bank). The revetment toe (consisting of armor stone, filter layer, and geotextile filter fabric) would be buried a minimum of 5-feet deep into the existing beach. The toe protection is needed to provide stability against undermining at the bottom of the structure. Lastly, a sand cover or other form of sand mitigation could be added on the face of the revetment or seaward of the revetment; the volume and frequency of this sand placement would likely be determined during the Conservation Commission review process. Sand covers are not typically placed on the face of revetments (see photographs of typical revetments in Attachment B) but may be included for aesthetic reasons or to supply sand to the littoral system. Native vegetation could be planted above the revetment in the appropriate places to stabilize the upper bank. 3.1.2 Environmental Considerations The revetment will be sloped, and the stones placed to form a rough surface to maximize wave energy dissipation and minimize wave reflection to adjacent, unprotected areas. No construction or placement of sand fill would occur seaward of the Mean High Water line. 21597/Sconset 13 Erosion Control Recommendations for Sconset Thus, the revetment would not have any adverse effects on marine fisheries, shellfish beds, or other biological communities such as mole crabs which reside the swash zone. A sand cover could be included for aesthetic reasons and to provide sand to the littoral system to avoid impacts to adjacent beaches; however, a sand cover is not necessary for the revetment to effectively protect the toe of the coastal bank. 3.1.3 Regulatory Considerations The Massachusetts Wetlands Protection Act (WPA) and Nantucket Wetlands Bylaw and regulations (Bylaw) have specific provisions governing the installation of a coastal engineering structure such as a revetment. The revetment will be placed on the face of the lower coastal bank, and the toe portion of the revetment will be buried at the interface between the coastal bank and coastal beach.  Under the WPA, coastal engineering structures are allowed to prevent storm damage to pre-1978 buildings. The protected structures can be on the water or land side of the road. Additionally, protection across “gap lots” between pre- 1978 homes may also be permitted.  Under the Nantucket Wetlands Bylaw regulations, coastal engineering structures are allowed on a coastal bank to protect public infrastructure, or pre-1978 structures that have not been substantially improved, from imminent danger.2 A revetment on a coastal bank is thus permissible. Coastal engineering structures are also allowed on a coastal beach to protect pre-1978 structures that have not been substantially improved from imminent danger.3 A revetment on a coastal bank and coastal beach is thus permissible, but may require determinations or waivers by the Town and Conservation Commission. Additionally, §67-1 of the Code of the Town of Nantucket provides for a temporary moratorium (ending December 31, 2013) on coastal engineering structures on Town-owned land from Great Point south to and including the Sconset sewer beds. Subsection D provides for an exception from the moratorium for emergency actions to protect public 2 NAN2.05(B)1. “No new bulkheads, coastal revetments, groins, or other coastal engineering structures shall be permitted to protect structures constructed, or substantially improved, after 8/78 except for public infrastructures. Bulkheads and groins may be rebuilt only if the Commission determines there is no environmentally better way to control an erosion problem, including in appropriate cases the moving of the threatened buildings and/or public infrastructure. Other coastal engineering structures may be permitted only upon a clear showing that no other alternative exists to protect a structure that has not been substantially improved or public infrastructure built prior to 9/78, from imminent danger.” 3 NAN 2.02(B)2. “No new bulkheads or coastal engineering structures shall be permitted to protect structures constructed, or substantially improved, after 8/78. Bulkheads may be rebuilt only if the Commission determines there is no environmentally better way to control an erosion problem, including in appropriate cases the moving of the threatened building. Other coastal engineering structures may be permitted only upon a clear showing that no other alternative exists to protect a structure built prior to 9/78, and not substantially improved, from imminent danger.” 21597/Sconset 14 Erosion Control Recommendations for Sconset infrastructure: “This moratorium shall not prohibit emergency armoring measures necessary to protect public roads, public buildings, or other public assets from imminent destruction.” In the case of Sconset, Baxter Road is clearly threatened as well as public property assets. 3.1.4 Cost The cost of installation and maintenance is comparable or lower than a marine mattress/gabion system, and is substantially lower than terraces. 3.1.5 Construction Information Approximately 8-10 weeks would be required to install the 551-foot section of revetment. Approximately 1500-feet of revetment could be installed to protect the most severely threatened homes from 73 Baxter to the Lighthouse in approximately 4 months. Construction could occur from August or September into early December. It is highly likely that the construction would be staged from the beach, with barges bringing in rocks and other supplies and offloading them to a barge anchored at the beach with a gangway to the beach. This approach would avoid truck traffic on local roads during the late summer. 3.1.6 Assessment of Effectiveness Revetments are a common coastal structure used for erosion control along shorelines in the northeast due to their proven effectiveness and the availability of suitable rock from local quarries. Numerous examples exist of successful revetment projects that have been constructed along Cape Cod and Southeastern Massachusetts. Examples of several such revetment projects are provided in Attachment B, which includes photographs of revetments in Plymouth, Scituate, Hull, Marshfield, and Nantucket. Like Sconset, the revetments included in Attachment B were installed on a coastal bank in a location facing open water. This information shows that revetments can be used for long-term, effective protection of public infrastructure and homes. 3.2 Public Benefits Erosion protection at Sconset would provide the following public benefits:  Protection of Baxter Road and associated utilities.  Preservation of historic homes and historic settings, as well as the relocated but still ultimately endangered Sankaty Head Lighthouse.  Preservation and possible restoration/expansion of the ‘Sconset Bluff Walk.  Preservation of tax revenue for Town of Nantucket and restoration of significant future tax revenues from deeply depreciated currently threatened properties. 21597/Sconset 15 Erosion Control Recommendations for Sconset  Preservation of private funding sources for erosion control efforts that protect Baxter Road through retention of private homes on Baxter Road, both now and in the future.  Possible inclusion of additional points of beach access to the general public. 3.3 Obtaining Environmental Approval for Recommended Action As indicated above, it is critical that the most vulnerable section of Baxter Road (from 99- 105 Baxter Road) is protected prior to the 2013-2014 winter storm season, or it is highly likely that part of Baxter Road will have to be closed or will actually be lost by slumping associated with ongoing bank erosion. Likewise, it is necessary to provide imminent protection for most of the homes from 73 Baxter Road north to the Lighthouse, since most of these homes could be lost during one severe storm season. A revetment would require both the support of the Board of Selectmen and approval from the Nantucket Conservation Commission. Such approval would be required by July in order to meet the following scheduling requirements:  Installation of the system must be completed by late fall to provide protection from winter storms.  Approximately 6 weeks will be required to prepare a request for proposals, solicit bids, and select a contractor.  Installation of the system will require 8-10 weeks for a 551-foot long stretch; or 4 months for an up to 1500-foot long stretch. Under these timeframes, approval from the Conservation Commission by July would be necessary, to allow selection of the Contractor by August, with construction to commence in mid-August or September and finish no later than early December. There are two potential means through which a revetment project could receive authorization from the Conservation Commission: as an “Emergency Project” or through the typical Notice of Intent (NOI) review process under the WPA and Bylaw. Each of these options is discussed below. 3.3.1 Emergency Project Approval The procedure for obtaining approval for an emergency project is outlined in the WPA regulations at 310 CMR 10.06 and described below:  The Conservation Commission or DEP Commissioner has to certify the project as an "emergency." 21597/Sconset 16 Erosion Control Recommendations for Sconset  An emergency certification can be issued only for "the protection of public health or safety."  The Conservation Commission has 24 hours to act after receiving the application form.  The timeframe for work to be performed is only 30 days, unless the DEP Commissioner approves the extension.  The only work allowed is that which would "abate" the emergency.  There is an appeal period associated with the emergency action approval, but work can occur during the appeal period. The protection of Baxter Road for the 551-foot section from 99-105 Baxter Road may potentially qualify as an emergency, although this is not certain. If the project were certified as an emergency, a timeframe longer than 30 days would have to be approved in order to allow the 8-10 weeks needed for revetment installation from 99-105 Baxter Road or the 4 month installation timeframe required for a 1500-linear foot revetment. Typically emergency certification is given after an emergency such as a major storm has occurred and immediate action is needed to abate the emergency conditions created by the storm damage. In the case of Sconset, an emergency certification would have to be granted under a more pro-active approach where the foreseeable loss of Baxter Road and/or homes is imminent but has not yet occurred. 3.3.2 Normal (Non-Emergency) Project Approval The normal procedure for obtaining approval for a project under the WPA and Bylaw involves the submission of a NOI followed by one or more public hearings, after which an Order of Conditions (OOC) is issued. Following the issuance of the OOC, there is a 10 business day appeal period under the WPA regulations and a 20 day appeal period under the Nantucket Wetlands Bylaw. In order for the revetment to be installed prior to the 2013-2014 winter storm season, the revetment must receive Conservation Commission approval during the month of July. A NOI would have to be filed in late June or early July in order to be heard by the Commission in July. The Conservation Commission would have to be prepared to address any questions or concerns about the project within one hearing and to issue an Order of Conditions soon after the close of the single public hearing. 21597/Sconset 17 Erosion Control Recommendations for Sconset 3.4 Conclusions Immediate protection of Baxter Road is critical for the 551-foot stretch from 99-105 Baxter Road, where the distance between the road and the top of the coastal bank is less than 45 feet (this distance ranges from 29 to 44 feet). Immediate protection of Baxter Road is also necessary for all remaining homes along Baxter Road from 73 Baxter to the Lighthouse, to protect both Baxter Road and threatened homes that are as close as 11-feet to the top of the coastal bank. Most of the homes from 73 Baxter Road north to the Lighthouse would be lost if another severe winter occurred. A rock revetment would provide effective protection in a high-energy environment like Sconset with no significant adverse environmental impacts; the cost of this alternative is comparable to, or lower than, the other alternatives. Given the high erosion rates of the coastal bank (up to 25 feet or more of the bank can be lost in one strong winter storm season), it is critical that the revetment is installed by late fall 2013. Meeting this schedule would require authorizing the revetment as an “Emergency Project” under the WPA or obtaining Conservation Commission approval for the project in a single public hearing during the month of July. Following this approval, contractor selection could occur in August, and revetment installation could occur from mid-August or early September through early December, depending on the length of revetment installed. In addition to the areas requiring immediate protection, near term (2014) protection of Baxter Road is also recommended for the remaining stretch of Baxter Road from 53 Baxter to the Lighthouse. The significant erosion occurring along Baxter Road from 2012-2013 underscores the point that this entire section is vulnerable to erosion and should be protected as soon as possible. Attachment A Figures Figure 1 Aerial Locus Map Figure 2 Current Setback of Road and Houses to Top of Bank, 93 to 105 Baxter Road Figure 3 Current Setback of Houses to Top of Bank, 69 to 83 Baxter Road Figure 4 Current Setback of Houses to Top of Bank, 109 to 115 Baxter Road Typical Revetment Section Figure 1Aerial Locus Map Nantucket, Massachusetts G:\Projects\Lighthouse\2013\aerial3.mxd LEGEND Basemap: 2012 Bing Aerial Imagery, ESRI °0 150 30075 Feet1 inch = 300 feet Scale 1:3,600 Parcel Boundary Figure 2. Current Setback of Road and Houses to Top of Bank93 to 105 Baxter RoadLot 99Lot 101Lot 105Road Setback44’Lot 93Lot 97Road Setback37’Road Setback29’House Setback8’House Setback24’ Figure 3. Current Setback of Houses to Top of Bank69 – 83 Baxter RoadLot 75Lot 79Lot 8111’ setback13’ setback18’ setbackLot 73Lot 71Lot 69Lot 83 Figure 4. Current Setback of Houses to Top of BankLots 109 - 115Lot 109Lot 113Lot 11511’ setback13’ setback18’ setbackFormer Location of Lighthouse Attachment B Revetment Examples Figure B-1 Hull, Point Atherton Revetment Figure B-2 Hull, Green Hill Revetment Figure B-3 Scituate, Fourth Cliff Revetment Figure B-4 Plymouth, Gurnet Revetment Figure B-5 Plymouth, Cedarville Landing Revetments Figure B-6 Nantucket, Capaum Pond Road Revetment Figure B-7 Nantucket, Westcliff Lane Revetment ^_ ^_ ^_ ^_ ^_ ^_^_ Gurnet Revetment, Plymouth, MA Green Hill Revetment, Hull, MA Point Allerton Revetment, Hull, MA Fourth Cliff Revetment, Scituate, MA Westcliff Lane Revetment, Nantucket, MA Capaum Pond Road Revetment, Nantucket, MA Cedarville Landing Revetments, Plymouth, MA Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User CommunityFigure 1Existing Revetments Nantucket, Massachusetts G:\Projects\Lighthouse\2013\revetments.mxd LEGEND Existing Revetment Location^_°0 4.5 92.25 Miles1 inch = 9 milesScale 1:570,240 Figure B-1 – Hull, Point Atherton Revetment Figure B-2 – Hull, Green Hill Revetment Figure B-3 – Scituate, Fourth Cliff Revetment Figure B-4 – Plymouth, Gurnet Revetment Figure B-5 – Plymouth, Cedarville Landing Revetments Figure B-6 – Nantucket, Capaum Pond Road Revetment Figure B-7 – Nantucket, Westcliff Lane Revetment Attachment J Milone & MacBroom Letter with Alternatives Analysis (dated October 25, 2013) Attachment K Supplemental Information for Notice of Intent (dated March 14, 2014) BAXTER ROAD TEMPORARY STABILIZATION PROJECT NOTICE OF INTENT (DEP FILE NO. SE 048-2610) SUPPLEMENTAL INFORMATION FOR MARCH 19, 2014 HEARING March 14, 2014 1. Geotube Information A. Proposed Fourth Tier of Geotextile Material SPBF and TON request that the Commission approve a fourth tier of geotextile material to complete the existing system. The engineering criteria used to design the geotube project (such as water level heights, anticipated wave runup, scour, etc.) are set forth in the attached memo from Ocean and Coastal Consultants (OCC) dated December 6, 2013 and submitted to the Commission as part of the Emergency Certification application filed on December 17, 2013. These design criteria clearly demonstrate the need for protection of the coastal bank up to elevation 24.2 Mean Low Water (MLW). Standard geotube dimensions put the top elevation at +26 ft MLW As shown on the attached As-Built plan, the current 3-tier geotube system extends to elevation ~21 MLW and is not considered adequate for the coastal environment at Sconset. A fourth tier of protection is required to achieve the design elevation of +26 MLW. The recommended material for the fourth tier is geotextile tubes. Understanding that the Commission wanted to evaluate the use of biodegradable materials (coir and/or jute), OCC has further analyzed the use of jute or coir to form the upper (fourth) tier of protection. The analysis performed by OCC in the attached memo dated March 13, 2014 demonstrates that a fourth tier made out of coir and/or jute will be expected to fail during the design storm event, leaving the coastal bank vulnerable at the time when protection is most critically needed. Additionally, as further described in OCC’s memo, the required sacrificial sand volume of 22 cy/lf requires the use of a bulldozer and/or excavator perched on the top row of protection to spread the sand dumped over the top of the bank by the conveyor belts1. OCC’s analysis indicates that the use of jute and/or coir for the top layer risks not being able to withstand the equipment loading and shear stresses caused by the tracks operating on the jute and/or coir, potentially causing the biodegradable material to fail under the weight of the equipment as sand is moved to cover areas of the template exposed by wave action.. For all these reasons, OCC 1 Maintenance of the terraces requires the use of a much lighter skid steer; however, a skid steer is simply not adequate for the additional length and volume of the geotube project. Additional Information for March 19, 2014 Conservation Commission Meeting 1 does not recommend the use of jute and/or coir for the fourth tier of protection. Similarly, the use of jute and/or coir for the third tier of protection is even more certain to result in failure and will cause serious difficulties in sand delivery; therefore, the use of jute/coir for the third tier is not considered a feasible option. Experience with the terraces suggests that biodegradable materials (jute and/or coir) may require complete replacement 1-3 times each year. This will require more frequent use of equipment at the top and toe of the bluff for sand delivery. Likewise, any sand contribution volume provided by complete emptying of two 15- foot circumference biodegradable tubes would be minimal, on the order of approximately 1 cy/lf. Biodegradable materials are not recommended given their clear engineering and feasibility drawbacks, as well as their minimal sand contribution. Further, the state Department of Environmental Protection (DEP) approved an Emergency Certification request for the four geotube design (see attached cover letter and Order of Conditions). In its cover letter dated December 10, 2013, DEP states the following: “The Department also applied the criterion at 310 CMR 10.30(3), which provides that a coastal engineering structure ‘shall be permitted’ to protect homes constructed prior to 1978 from storm damage. This regulation creates an exception to the general rule that precludes the installation of hard armoring of coastal banks. Based on the facts presented in the Request, this exception applies to the homes identified in the area subject to the determination of an emergency…. “The Department concludes that the [four tube] design of the coastal structure proposed in the Request does not go farther than necessary to protect these homes and essential public infrastructure serving the homes. In making this determination, the Department considered the specific facts presented by the proponents, including, without limitation, the proximity of the homes and infrastructure to the edge of the coastal bank, the ability of the four Geotubes to withstand a significant storm event and the threat posed by successive storm events…. “The implementation of the nourishment plan will mitigate any potential difference in down drift impacts between the four Geotube design and the hybrid design approved in the Town's Certification.“ Additional Information for March 19, 2014 Conservation Commission Meeting 2 B. Proposed Returns for Geotube SBPF and TON request that the Commission approve the installation of returns at the ends of the system. The use of returns is critical to protect the geotube system from flanking and end scour over the long-term. SBPF proposes the use of 15-foot circumference geotextile tubes as shown on the attached plan, installed at shallow angle between the face of the seaward geotubes and the face of the unprotected bluff. Geotextile material is strongly preferred because it can better withstand the coastal conditions at Sconset than biodegradable material (as described under 1A). C. Revised Location and Length of Geotubes SBPF and TON are informing the Commission of the reduction in length of the installed system. The Emergency Certification approved a length of just under 900 feet long from 91- 105 Baxter Road. The as-built geotube structure is approximately 852 feet long2 from 87-105 Baxter Road. The presence of the clay head at 105 Baxter Road dictated that the geotube structure should not be installed farther to the north (or else excavation into the bluff would have been required), so the installation was shifted slightly to the south. The multiple geotubes installed along the same tier also overlap one another slightly at each end, leading to a slight reduction in overall length (to 852 feet) from the permitted dimension of just under 900 feet . Each return is approximately 21-feet long (as shown on the attached plan) . Once the returns are installed, the total installed length will be approximately 900 feet. The project does not intend to proceed farther north than currently built, due to the presence of the clay head that would require excavation into the coastal bank. Similarly, the project does not intend to proceed farther south. Therefore, the final project length will be less than the 1500-feet originally proposed. D. Construction Information SPBF and TON are providing additional details on construction. o Sand Delivery. Sand delivery occurred at the delivery locations at 87 Baxter Road and 99/101 Baxter Road. These two locations will continue to be used for ongoing sand cover maintenance. o Geotube Fill Port Closure. As detailed in the letter from SBPF dated February 12, 2014, the use of a small amount of concrete was required to seal the fill ports in the geotubes. The installer has confirmed via email of February 12, 2 The as-built plan shows that the first and second geotubes are 852± feet long. The third (upper) geotube is 835± feet long. Additional Information for March 19, 2014 Conservation Commission Meeting 3 2014 (previously submitted to the Commission) that this approach is standard procedure. Approximately one-third or less of a bag of concrete was used at each fill port. The size has been compared to a deflated soccer ball. o US Army Corps of Engineers (USACE) Jurisdiction. Concern has been expressed about whether work was carried out below the High Tide Line. SBPF submitted information to the USACE at the end of December 2013 relating to the concern. Subsequent to the letter issued by the USACE in February 2013, SBPF again engaged with the USACE concerning its written inquiry of possible work below the High Tide Line. As indicated in the exchange with the USACE, the HTL was staked on the beach at the beginning of construction. The construction crew was aware of the HTL location on the beach and made every effort to stay landward of that line. The USACE informed SBPF that no further action is needed or planned and that no Federal order or violation notice has been issued or is planned. As we understand it, the USACE considers the matter of the geotube construction to be closed. However, to be safe, SBPF has provided the USACE with details on how future maintenance and sacrificial sand will be done to make sure that the USACE does not have any concerns with those future actions. Attached please find the original December 2013 update to the USACE regarding the geotube installation, which they acknowledge that they received and then misplaced, contributing to the inquiry, as well as Epsilon’s February 26, 2014 summation letter after the later discussions. 2. Stormwater Drainage SBPF requests that the Commission permit the installation of a stormwater drain along 91 Baxter Road. Surface water runoff at 91 Baxter Road was contributing to significant erosion of the bank face. . The advising geotechnical engineer, Mark Haley of Haley & Aldrich, a well-respected geotechnical engineering firm with substantial experience on the Sconset Bluff, suggested that a subsurface drainage system be installed to direct the surface water runoff to the toe of the bank, rather than allowing it to break out on the bank face and cause additional erosion. A memo from Mark Haley dated March 12, 2014 describing his recommendations is attached. The subsurface drain was installed at 91 Baxter Road, parallel to and approximately 10 feet seaward of the roadway, for a distance of approximately 41 feet. The subsurface drain consists of an 18 inch deep x 18 inch wide trough that is lined with filter fabric and holds a 4” diameter corrugated pipe. The trough is backfilled with ¾ inch gravel. The subsurface drain collects stormwater runoff and directs it to another 4” diameter PVC pipe that runs down the face of the bank and terminates at the toe of the bluff, in a gravel trough placed in the sand template behind the Additional Information for March 19, 2014 Conservation Commission Meeting 4 geotubes. No excavation into the bank or beach occurred to install the PVC pipe that runs down the face of the bank; this pipe was placed within sand added to the bank face or the sand template on the geotubes. Although the pipe was installed because of construction timing, it was understood to require approval from the Commission before it was completed. The pipe was never connected and is not functioning. SBPF is requesting approval for the subsurface drain. 3. Bluff Protection through Re-vegetation SBPF and TON request approval to vegetate the upper bank, including smoothing or dressing the bank face to create an acceptable planting bed and using an erosion control fabric or biodegradable netting. The upper portion of ‘Sconset bluff (above the geotube installation at 87-105 Baxter Road) exhibits evidence of rill erosion from rainfall and stormwater runoff from the top of the coastal bank. The attached Photographs 1-4 show the development of rivulets and small gullies in the bank face. While the geotubes have served to protect the toe of the coastal bank from waves and storm surges, erosion of the upper bank due to runoff over the bank surface and slumping due to gravity mass failure will likely continue unless additional measures are undertaken to protect this bank area. See attached memo from Mark Haley dated March 12, 2014, on the need for vegetation of the bank face. It is critical to address this upper bank erosion within the project area, as the loss of even a few feet of bank leaves Baxter Road potentially vulnerable to closure. As was previously submitted to the Commission, Mark Haley recommends a minimum distance of 25-feet be maintained between the edge of pavement and top of the bluff. When the top of bluff is within 25 feet of the pavement edge, a detailed assessment should be completed by a geotechnical engineer and the possibility of the road being closed should be carefully considered. Field measurements and aerial surveys performed in summer 2013 indicate that the distance between the top of the bluff and the edge of Baxter Road is as close as 30 to 40 feet from the edge of Baxter Road in several areas, and is 60 to 70 feet away in many areas. Subsequent discussions with Mark Haley and other erosion control professionals indicate that the most effective means of addressing the upper bank erosion will be through the planting of native vegetation with strong underground stems (rhizomes), such as American beachgrass, or other native vegetation with an extensive root system. (Bank “augmentation” is also beneficial; this is further discussed in #4C below.) To ensure vegetation efforts are successful, , some addition of sand is needed to prepare the planting bed prior to planting. . This sand will be provided from on-island sand pits by the conveyor belt system utilized during the geotube Additional Information for March 19, 2014 Conservation Commission Meeting 5 construction process. The use of a biodegradable erosion control fabric or jute netting is also proposed to protect soil from wind and water erosion, and retain moisture to facilitate establishment of vegetation. In his memo dated March 12, 2014, Mark Haley recommended the vegetation of the bluff and noted that it would “increase face stability and reduce erosion of the slope above the geotubes due to rain events.” The preferred type of vegetation for initial planting is American beachgrass; additional native vegetation (such as woody shrubs) may be planted subsequently. The USDA Natural Resource Conservation Service’s (NRCS) Plant Guide for American beachgrass (attached) states that the optimal time to plant the bank face is October 1 through March 30, and that this period may be extended through April 30 in New England in most seasons. Discussions with two suppliers of American beachgrass to Nantucket confirm that the best possible time for planting beachgrass is before mid-April. Further, planting at this time allows the American beachgrass one full growing season for rhizome development and the associated benefit to bank stability, prior to the start of the winter storm season. Given how little bank loss can be tolerated in the project area before road closure is required, it is critical to protect the upper bank face from ongoing erosion by establishing vegetation this growing season. Finally, fertilizer applied on the schedule listed in the Plant Guide is strongly recommended by the NRCS as the key to vigorous growth. SBPF and TON propose to follow the fertilizer guidelines established by NRCS. Based on discussions with two local companies, the preferred type of American beachgrass is referred to as “bare root.” The “bare root” type must be planted by mid-April and will result in fuller plant and rhizome development by the fall. Use of the “bare root” type would provide substantial protection to the upper bank by the end of the 2014 growing season. The less preferred option is the “root ball” type, which can be planted after mid-April but would require two growing seasons to develop as fully as the “bare root” type, meaning that the upper bluff would only have marginal protection until the end of the 2015 growing season. Within the project area, the planting of vegetation will occur entirely on private property. The establishment of vegetation not only stabilizes the coastal bank, but also contributes to wetland scenic view and wildlife habitat with no negative impacts. It is clear from the planting of beach grass in other locations on the bluff in recent years that this vegetation will be successful in stabilizing the face of the bluff and encouraging infiltration (instead of run-off and erosion), now that the toe has been protected and the vegetation will not be undermined. Additional Information for March 19, 2014 Conservation Commission Meeting 6 4. Sand Contributions, including Sand Volumes (for construction and sacrificial template), Schedule of Future Contributions/Maintenance, and Bluff Face Augmentation. A. Sand Volume Delivered During Construction SBPF and TON are presenting documentation that the required volume of sand was provided. The attached Table 1. “Summary of Sand Delivery Requirements for ‘Sconset Geotube Project, 87-105 Baxter Road, Nantucket, MA” demonstrates that the project met its sand delivery requirements. The volume of sand required to construct the geotubes (sand fill required in the tubes, sand fill required behind the tubes to create the “benches,” sand for the 22 cy/lf sand cover) totals 31,396.50 cy. The sand delivered was in excess of this requirement at 39,204.24 cy. The 7,807.74 cy of surplus sand was used at the sand delivery locations, on the face of the bluff, at the ends, for construction, etc. The attached Table 2. “Record of Individual Truck Deliveries for ‘Sconset Geotube Project, 87-105 Baxter Road, Nantucket, MA” provides a detailed inventory of individual truck deliveries, including invoices and receipts. B. Sand Maintenance Plan and Delivery Schedule. SBPF and TON are presenting information on the volume and delivery schedule for the sand cover. Considerable documentation has been previously provided that the average annual volume of bank erosion is equivalent to 14.3 cy/lf/yr (see November 1, 2013 submission). SBPF and TON will accept a sand mitigation requirement of 22 cy/lf/yr, in accordance with the recommendation from the DEP that additional sand be contributed for now, based on its finding that: “The implementation of the nourishment plan will mitigate any potential difference in down drift impacts between the four Geotube design and the hybrid design approved in the Town's Certification. “ (See attached December 10, 2013 cover letter from DEP.) The 22 cubic yards per linear ft (cy/lf) of sand will be delivered in accordance with the following schedule: o Provide the initial cover of 22 cy/lf during and/or immediately following construction. o Annually in April starting in 2014: Provide additional sand and/or adjust the existing template sand to obtain a minimum of 2 feet of cover over the geotubes to protect them from UV degradation. If some portion of the previous year’s sand is in place at the time of April nourishment, then only that volume needed to provide the 2 feet of cover will be added. The Additional Information for March 19, 2014 Conservation Commission Meeting 7 volume of any sand placed in April will be recorded and counted towards the annual 22 cy/lf requirement. o Annually in November starting in 2014: Place an additional 10-15 cy/lf of sand, to ensure a substantial portion of the sand template volume is available at the onset of the winter storm season. Throughout the winter, place additional sand on an as-needed basis, in accordance with the replenishment trigger presented in our November 12, 2013 letter (i.e., if half the vertical height of the lowest geotube is exposed, place a minimum of 2 cy/lf). If the balance of the 22 cy/lf volume is not placed in its entirety during the 2014-2015 winter, the balance of the sand will be placed by March 31, 2015. o Delivery tickets from sand suppliers will be provided to the Conservation Commission to document the total volume of sand provided on an annual basis (April 1- March 31 of any given year). The attached Tables 1 and 2 provide, respectively, a summary of how the project met its sand delivery requirements as well as a detailed inventory of individual truck deliveries and receipts. C. Bluff Augmentation SBPF and TON are requesting approval of bluff augmentation to further stabilize the bluff. As described above under #3, in the attached photographs, and in the memo from Mark Haley dated March 12, 2014, the existing coastal bank above the geotubes remains susceptible to erosion from rain and stormwater runoff. The bluff is particularly unstable in those portions that are over-steepened at the top, which are highly susceptible to further collapse, potentially leading to additional catastrophic losses at the top of the coastal bank. To address these issues, it is proposed to “augment” the existing coastal bank in the project area by adding compatible sand to the face of the coastal bank, via the same conveyor belt system used to provide the sand cover on the geotubes. Mark Haley of Haley & Aldrich, in his memo dated March 12, 2014, has indicated that: “Adding sand to the face of the slope, especially near the top of slope where the slope is near vertical, will greatly increase the stability of the bluff.” During the construction process, additional sand was placed at or near the sand delivery locations at 87/91 and 99/101 Baxter Road (see attached Photograph 5). It has been observed that this sand acted to protect the face of the bluff because it increased infiltration of rain and surface water runoff and also attenuated soil erosion from rain and surface water flows. In the areas where the face of the bluff Additional Information for March 19, 2014 Conservation Commission Meeting 8 was not augmented with additional sand, surface water flows continued to erode that portion of the bluff above the geotubes. SBPF and TON are requesting approval of the existing bluff augmentation now in place at or near the two sand delivery locations (87/91 and 99/101 Baxter Road), as well as the proposed added augmentation at 93 Baxter Road, where the existing pre- 1978 dwelling is less than 8 feet from the top of bank and is in imminent danger. Immediate bluff augmentation efforts at 93 Baxter Road, combined with vegetation, could stabilize the entire bluff and prevent the loss of this pre-1978 structure. We note that adding this sand has no negative effect: it is bank- and beach- compatible and will either remain in place or run down to the geotube template or the beach for contribution to the littoral system. List of Attachments 1. Memo from Ocean and Coastal Consultants, dated March 13, 2014 2. DEP Emergency Certification Approval (cover letter and Order of Conditions), dated December 10, 2013 3. Plan and Isometric View of Returns 4. USACE Correspondence (emails from Epsilon to USACE dated December 27 and 30, 2013 and letter from Epsilon dated February 26, 2014) 5. Memo from Mark Haley dated March 12, 2014 6. Photographs 1-5 of Sconset Bluff 7. Natural Resource Conservation Service’s Plant Guide for American beachgrass 8. Table 1. “Summary of Sand Delivery Requirements for ‘Sconset Geotube Project, 87-105 Baxter Road, Nantucket, MA” 9. Table 2. “Record of Individual Truck Deliveries for ‘Sconset Geotube Project, 87- 105 Baxter Road, Nantucket, MA” 10. Response to Nantucket Land Council Letter dated February 18, 2014 11. Approximate Sand Template Additional Information for March 19, 2014 Conservation Commission Meeting 9 Ocean and Coastal Consultants, Inc. (OCC) performed a runup and overtopping analysis on the proposed "hybrid" stabilization system consisting of three (3) tiers of geotubes to elevation +21 ft MLW followed by jute/coir bags above. Coastal design parameters such as water levels, wave heights, setup, etc. as outlined in OCC's memo titled "Sconset Coastal Analysis Summary" dated December 6, 2013 were utilized in the analysis. Below elevation 18 ft MLW, the structure is subject to direct wave attack from 100- year storms. At elevation 21 ft MLW, where the fourth tier is proposed, the jute/coir bags will be subjected to wave runup and subsequent overtopping forces. Wave runup and overtopping was calculated on the stacked geotube system in accordance with USACE Coastal Engineering Manual (CEM) methodology for a berm configuration based on the as-built geometry in which the third tube is set back approximately 11.5 ft from the front of the middle tube; the top of the third tube is at approximate elevation of +21 ft MLW with jute/coir bags above set back approximately 11.5 ft to maintain the existing slope. The attached spreadsheet using Equation VI-5-7 of the CEM indicates that wave runup will be 10.4 ft. with average overtopping rate (q) of 1.7x10-2 m3/s per m (17 l/s per m). The USACE CEM Table VI-5-6 provides critical values of average overtopping discharges and the rate at which various structures may sustain damage. According to the table, at 1x10-2 m3/s per meter, a grass sea-dike will be damaged. A grass sea-dike would be most similar to jute- or coir-covered slope so this overtopping rate will likely cause damage to the jute/coir bags. The wet tensile strength of jute/coir products is 21.7 kN/m (machine direction) and 15.1 kN/m (cross direction) while the recommended shear stress is 0.215 kN/m2 (see attachment). The Wave Overtopping of Sea Defences and Related Structures: Assessment Manual provides a graph of equivalent pressure for overtopping rates based on model studies (attached). The equivalent pressure for 17 l/s/m of overtopping will be in excess of 25 kPa (25 kN/m2) which is greater than the strength of the material. As a result, it is expected that the jute bags will be torn open under wave overtopping pressures of the 100-year storm event. MEMO TITLE Sconset Hybrid System Runup and Overtopping DATE 13 March 2014 TO SBPF COPY Epsilon Associates FROM Azure Dee Sleicher, P.E. PROJECT NO 210019.1 ADDRESS Ocean and Coastal Consultants, Inc. 35 Corporate Drive Suite 1200 Trumbull, CT 06611 TEL 203-268-5007 FAX 203-268-8821 WWW ocean-coastal.com PAGE 1/2 PAGE 2/2 Since jute/coir products are susceptible to being ripped open by the forces of storm waves, it is possible that they may need to be replaced 1-3 times per year. This replacement can not always occur in a timely fashion during multi-day or rapid succession storms resulting in loss of protection at a time when it is most needed. Frequent replacement of jute/coir products results in additional truck traffic and added costs. Lastly, the project requires a substantial volume of sacrificial sand (22 cy/lf) to be placed on top of the geotubes. To spread this volume, a bulldozer (D6 dozer – 18 tons) and/or an excavator (336 excavator – 40 tons) will be required to be perched on top of the 4th row of tubes. It is unlikely that a 4th row of jute/coir will be able to withstand the required loading and shear stresses caused by the equipment operating on top of the sand-filled jute bag. For all of the reasons stated above, it is not advisable that jute/coir be used as a substitution for proper geotextile tubes (geotubes). Sconset, Nantucket Geotube Runup and Overtopping Analysis Ocean and Coastal Consultants March 2014 Equivalent and Average Slopes (aeq, a): CEM EQ. VI-5-8 and VI-5-9, Figure VI-5-7 (below) Input: a1 a2 Hs (feet)Tp (sec)B (feet)Rc (feet) 2 d (feet) 3 60 60 5 15.2 11.5 11.1 6.1 1 - negative if SWL is below berm, positive if SWL is above 2 - freeboard: top of berm above SWL 3 - water depth from toe of berm to SWL Output: aeq a 30.07 60 rB 0.67 rdB 2.46 gb 1.97 Runup and Overtopping Check: CEM EQ. VI-5-24 and VI-5-25 Sop 0.00 gr 0.90 relatively "smooth" slope ξop 26.64 ξeq 52.62 gB 1 gh 0.77 Ru2% (feet)10.37 CEM EQ. VI-5-7 q 1.72E-02 m3/s per m * - see Table VI-5-6 if more conservative limits of overtopping are required 0.6 ≤ gb ≤ 1.0 Optimum value is 0.6 Allowable Limit* = 1E-03 m3/s per m SWL (feet below berm)1 -11.1 Page 1 Sconset, Nantucket Geotube Runup and Overtopping Analysis Ocean and Coastal Consultants March 2014 x y x y x y x y 0 0 0 0 11.5 0 -2.89 -5 -5.77 -10 11.5 0 17.27 10 14.39 5 -19.92 0.58 x y x y x y -5.77 -11.1 0 0 -9.30 -16.1 17.27 -11.1 5.77 10 -3.52 -6.1 -8.9E-16 1.73 Hs y-intercept of a2 Hs y-intercept of a2 (transposed) a2 slope of Hs line a2 (transposed) Berm Width SWL slope of Hs line a1 -15 -10 -5 0 5 10 15 -10 -5 0 5 10 15 20 Equivalent Slope (Including Berm) a1 Berm Width a2 Hs -20 -15 -10 -5 0 5 10 15 -15 -10 -5 0 5 10 15 20 Average Slope (Excluding Berm) a1 Berm Width a2 SWL a2 transposed Hs Page 2 Sconset, Nantucket Geotube Runup and Overtopping Analysis Ocean and Coastal Consultants March 2014 17 l/s per m Page 3 37 33.2 Overtopping velocities Few data are available on overtopping velocities and their contribution to hazards. For simply sloping embankments Chapter 5 gives guidance on overtopping flow velocities at crest and inner slope as well as on flow depths. Velocities of 5-8 m/s are possible for the maximum overtopping waves during overtopping discharges of about 10-301/s per m width. Studies of hazards under steady flows suggest that limiu on horizontal velocities for people and. vehicles will probably need to beset below vX < 2.5 to 5 m/s. ALso refer to Section 5.5. Upward velocities (vZ) for vertical and battered walls under impulsive and pulsating conditions have been related to the inshore wave celerity, see Chapter 7. Relative velocities, vZ/ct have been found to be roughly constant at vZ/ci ~ 2.5 for pulsating and slightly impulsive conditions, but increase significantly for impulsive conditions, reaching v=/c+ ~ 3 — 7. 333 Overtopping loads and overtopping simulator Post-overtopping wave loads have seldom been measured on defence structures, build- ingsbehind sea defences, or on people, so little generic guidance is available. If loadings from overtopping flows could be important, they should be quantified by interpretation of ap- propriate field data or by site-specific model studies. An example (site specific) model study indicates how important these effects might be. A simple 1 m high vertical secondary wall was set in a horizontal promenade about 7 m back from the primary seawall, itself a concrete recurve fronted by a rock armoured slope. Pulsat- ing wave pressures were measured on the secondary wall against the effective overtopping discharge arriving at the secondary wall, plotted here in Fig. 3.3. This was deduced by apply- ingEquation 3.1 to overtopping measured at the primary wall, 7 m in front. Whilst strongly site specific, these results suggest that quite low discharges (0.1-1.01/s/m) may lead to load- ings up to SkPa. 25 20 .v y 15 N ~ ~~ a` s a8 0 Overtopping discharge at the seawall [llslm] Fig. 3.3: Example wave forces on a secondary wall I~ ,Q ~s ~~, ~ ~ Z5 1~ P0. '----~ ~ 1 ~. ~ 5 ~ ~a5[~ 0/1 ~~~u~t 155 Andrew Drive, Stockbridge, GA 30281 1 800 760 3215 Tel: 770 506 8211 E-mail: rolanka@rolanka.com Fax: 770 506 0391 web: www.rolanka.com Manufacturer's Certificate of Compliance TO WHOM IT MAY CONCERN This is to certify that the BioD-MatTM70 woven coir blanket is woven from machine twisted coir twines made of bristle coir obtained from freshwater cured coconut husks. BioD-MatTM70 blankets are manufactured to conform to the following physical properties: Property Test Method BioD-MatTM70 1. Weight ASTM D 3776 23 oz/SY (780 g/m2) 2. Wide width tensile strength ASTM D 4595 Wet Machine direction 1488 lbs./ft (21.7 kN/m) Cross direction 1032 lbs./ft (15.1 kN/m) Dry Machine direction 1740 lbs./ft (25.4 kN/m) Cross direction 1176 lbs./ft (17.2 KN/m) 3. Elongation at failure ASTM D 4595 Wet Machine direction 38 % Cross direction 25 % 4. Number of twine in the mat Machine direction 82 twines /yard (90 twines / m) Cross direction 55 twines /yard (60 twines / m) 5. Open area Calculated 48 % 6. Thickness ASTM D 1777 0.35 inch (9 mm) 7. Recommended shear stress 4.5 lbs./sq.ft. (215 N/sq.m.) 8. Recommended flow 12 fps (3.7 m/s) 9. Recommend slope >1:1 10. “C” factor 0.002 RoLanka International, Inc. Calista R. Santha Calista R. Santha, Ph.D. President SBA’s 8(a) & SDB and DOT DBE Certified. Attachment L Alternatives Analysis for the (1) Fourth Tier of the Existing Three Tier Geotextile Tube Structures and the (2) Return Design (dated October 23, 2014) ALTERNATIVES ANALYSISALTERNATIVES ANALYSIS for the (1)Fourth Tier of the Existing Three Tier (1)Fourth Tier of the Existing Three Tier Geotextile Tube Structure and the Baxter Road and Sconset Bluff Stabilization Project (2) Return Design Baxter Road and Sconset Bluff Stabilization Project Nantucket, MA Submitted to:Pd bSubmitted to: Massachusetts Department of Environmental Protection – Southeast Region 20 Riverside Drive Lakeville, MA 02347 Submitted by Prepared by: Epsilon Associates, Inc. 3 Clock Tower Place, Suite 250 Maynard, Massachusetts 01754 In Association with:Submitted by: Siasconset Beach Preservation Fund PO Box 2279 Nantucket, MA 02584 In Association with: Ocean and Coastal Consultants, Inc. October 23, 2014 i. Baxter Road and Sconset Bluff i Alternatives Analysis Epsilon Associates, Inc. TABLE OF CONTENTS 1.0 INTRODUCTION 1 2.0 ALTERNATIVES FOR THE FOURTH TIER OF THE EXISTING THREE TIER GEOTEXTILE TUBE STRUCTURE 2 2.1 Alternative One: Jute or Coir Tubes 2 2.1.1 Ability to Provide Required Protection 2 2.1.2 Ability to be Constructed and Maintained 3 2.1.3 Potential Benefits and Impacts 6 2.1.4 Conclusions 8 2.2 Alternative Two: Geotextile Tube Combined with Jute or Coir Tubes 8 2.2.1 Ability to Provide Required Protection 9 2.2.2 Ability to be Constructed and Maintained 9 2.2.3 Potential Benefits and Impacts 10 2.2.4 Conclusions 11 2.3 Alternative Three: Geotextile Tube 12 2.3.1 Ability to Provide Required Protection 12 2.3.2 Ability to be Constructed and Maintained 12 2.3.3 Potential Benefits and Impacts 12 2.3.4 Conclusions 12 3.0 ALTERNATIVE DESIGNS FOR THE RETURNS 14 3.1 Original Return Design: Twenty 15-foot Circumference Geotextile Tubes 14 3.2 Alternative Return Concept One: Six 30-Foot Circumference Geotextile Tubes 15 3.3 Alternative Return Concept Two: Returns Constructed of Jute/Coir 15 3.4 Alternative Return Concept Three: Gabions or Rip Rap 16 3.5 Conclusions 17 ATTACHMENT: DRAWINGS SK-01 THROUGH SK-05 Baxter Road and Sconset Bluff 1 Alternatives Analysis Epsilon Associates, Inc. 1.0 INTRODUCTION The Baxter Road and Sconset Bluff Stabilization Project (EEA 15240), located at Sconset, MA, received its Certificate of the Secretary of Energy and Environmental Affairs on the Environmental Notification Form on October 3, 2014. The Secretary’s Certificate did not require the preparation of an Environmental Impact report and directed the Massachusetts Department of Environmental Protection (MassDEP) that, during the permitting process, alternative designs should be considered for (1) the fourth tier of the existing three-tier geotextile tube structure and (2) the end returns, using the following language: The feasibility and potential benefits and impacts associated with design alternatives for the fourth tier of the installation and the end returns [should be addressed during permitting.] On behalf of the project proponent, the Siasconset Beach Preservation Fund (SBPF), Epsilon Associates, Inc. has prepared the following Alternatives Analysis to evaluate such alternatives, for MassDEP to use during its review. In accordance with the Secretary’s Certificate, the Alternatives Analysis presented herein is limited to a review of design alternatives for the fourth tier and returns for the already-installed three tiers of geotextile tubes. This document is not intended to provide a comprehensive review of alternatives for long-term bluff protection. It is SBPF’s current view that the most reliable, fully tested, and low maintenance alternative for conditions in Sconset along the bluff would likely be a rock revetment. That alternative was not proposed or evaluated here because, as noted, this alternatives analysis is limited to a review of design alternatives for the fourth tier and returns for the existing geotextile tube project. The existing geotextile tube project was designed to address exigent circumstances which became emergency circumstances through a design that, in view of the demonstrated difficulty of obtaining approval for a revetment prior to the onset of the winter 2013-2014 storm season, could be permitted more expeditiously, and constructed quickly consistent with the emergency timeframe under which the project was operating. The description of the project is presented in detail in the Request for a Superseding Order of Conditions (SOC) and is not repeated here. Baxter Road and Sconset Bluff 2 Alternatives Analysis Epsilon Associates, Inc. 2.0 ALTERNATIVES FOR THE FOURTH TIER OF THE EXISTING THREE TIER GEOTEXTILE TUBE STRUCTURE In accordance with the Secretary’s Certificate, the following alternatives were considered for the 4th and/or 5th tiers of the coastal protection structure. Each alternative includes the same base of the existing three tiers of 45-foot circumference geotextile tubes: (1) Alternative One: Jute/Coir Tube(s) (2) Alternative Two: Geotextile Tube Combined with Jute/Coir Tube(s) (3) Alternative Three: Geotextile Tube Each alternative is evaluated below according to its ability to provide the required protection, ability to be constructed and maintained, potential benefits, and potential impacts. Alternatives are also evaluated according to the Wetlands Protection Act Regulations as listed in Section 310 CMR 10.30(3)(a): “a coastal engineering structure or a modification thereto shall be designed and constructed so as to minimize, using best available measures, adverse effects on adjacent or nearby coastal beaches due to changes in wave action….” “Best Available Measures” are defined in 310 CMR 10.04 as: “the most up-to-date technology or the best designs, measures or engineering practices that have been developed and that are commercially available.” These standards make it clear that coastal engineering structures should minimize adverse effects on adjacent beaches by using the best engineering practices and designs. The design elevation for the geotextile tube installation needed to provide protection during a 100- year storm is +24.1 feet on the Mean Low Water (MLW) datum, as presented in the memo provided by Ocean and Coastal Consultants included as an attachment to Exhibit Z in the Request for an SOC. The existing three-tier geotextile tube structure ranges in elevation from +18.9 MLW to +21.3 MLW (with an average elevation of +20.4 ft MLW), so up to an additional 5 feet of vertical protection are required for the upper tier(s) of the geotextile tube installation. The need for up to an additional 5 feet of vertical protection guided the selection of the size of the tubes utilized in the three alternative design concepts. 2.1 Alternative One: Jute or Coir Tubes In this alternative, two jute/coir tubes would be stacked on top of the existing three-tier geotextile tube structure. The use of two stacked tubes is required to reach the design elevation. Each jute/coir tube would be 30-foot circumference, with an approximate height of 3.5 feet. The tubes would be stacked so as to provide some overlap (see attached drawing SK-01). 2.1.1 Ability to Provide Required Protection Jute and coir fiber mats, bags, or envelopes have been used in select locations along Sconset Bluff and Beach in the past and are referred to as “terraces” due to their stepped Baxter Road and Sconset Bluff 3 Alternatives Analysis Epsilon Associates, Inc. design. The long history with the use of coir/jute terraces at Sconset has demonstrated that these biodegradable materials are not well suited to withstanding wave impacts associated with the Atlantic Ocean. The terraces are designed to release their sand and fail during storm events, leaving the coastal bank vulnerable during major, successive, or multi-day storm events. The terraces simply cannot withstand the storm conditions experienced regularly at the Project site. The failure of the jute terraces during storms means that all or part of the terraces must be replaced one to three times per year. The demonstrated failure of the jute/coir terraces and their subsequent need for frequent replacement also means that the coastal bank is left vulnerable during major, multi-day or successive storms. This was readily apparent at 79 Baxter Road, where the jute terraces had been regularly maintained for over 5 years. The jute envelopes had been replaced completely one to three times each year since they were installed. This frequent maintenance had led to reduced erosion of the coastal bank in this location until the jute terraces failed and could not be reconstructed during successive storms in the winter of 2012-2013, resulting in the loss of approximately 30 feet of the bank at the north end of the property. This experience demonstrates that jute is not an adequate material to withstand the extreme forces and successive storms that occur at the Project site. Additional engineering analysis of the use of coir/jute for the upper tiers demonstrated that these materials would be expected to fail during storm conditions (presented in the memo from Ocean and Coastal Consultants [OCC] dated March 13, 2014 included as an attachment to Exhibit U in the Request for an SOC), consistent with what has already been demonstrated through the historical use of coir/jute terraces at the Project site: [I]t is expected that the jute bags will be torn open under wave overtopping pressures of the 100-year storm event….[I]t is not advisable that jute/coir be used as substitution for proper geotextile tubes (geotubes). The project area does not have the capacity to absorb an additional 30 feet of bank loss, so the use of jute/coir is not advisable. In particular, pre-1978 homes are as close as four feet from the top of the bank (as shown on Exhibit Y in the Request for an SOC) and Baxter Road is as close as 29 feet from the top of the bank (as presented in Exhibits L and Y in the Request for an SOC). It has been suggested that the placement of additional nourishment material would allow jute/coir tubes to “stand up to more severe storms.” During severe storms, unconsolidated sand would be eroded and the jute/coir tubes would become exposed and deflated, allowing erosion and collapse of the bank. In conclusion, Alternative One does not provide the required storm protection. 2.1.2 Ability to be Constructed and Maintained Construction and maintenance of jute or coir materials poses significant concerns related to the ability to drive heavy equipment on the materials, the length of time required to replace the jute/coir, and the required removal or inability to replace the sand template for a period Baxter Road and Sconset Bluff 4 Alternatives Analysis Epsilon Associates, Inc. of six-eight weeks any time the jute/coir are required to be replaced. These concerns are detailed below:  Jute/Coir Subject to Degradation. The jute/coir can be expected degrade relatively quickly. The type of jute typically used at the site will degrade after 1-2 seasons. The use of multiple (three) layers of coir, or the use of multiple (three-four) layers of jute with a tighter weave but still porous nature, and/or the use of chemical coatings, may be able to extend the lifespan of the materials to approximately 3-4 years. Additionally, the jute/coir can be expected to require replacement after major storms. It is therefore anticipated that the jute/coir tiers would need to be completely replaced on a regular basis due to degradation or storms, likely every one-three years.  Jute/Coir May Not Support Required Equipment Loading; Special Equipment Required. Heavy equipment is needed to drive on top of the sand template to spread the substantial volume of the mitigation sand. This equipment includes an excavator (324EL excavator – 26 tons) and/or a bulldozer (D6 dozer – 18 tons). Engineering analyses (as presented in the memo from OCC dated March 13, 2014 included as an attachment to Exhibit U in the Request for an SOC) suggest that the porous coir or jute bags could not support the required equipment loading and shear stresses. This issue is especially critical after major storms when it can be expected that part or all of the 4th and 5th tiers may be exposed. Therefore, in order to rebuild the jute/coir tubes and spread the sand template, special equipment (in the form of a long reach excavator) would be required to rebuild and recover the jute/coir tubes from beach level. No long reach excavators are available on the island of Nantucket, so the excavator would need to be rented and mobilized to the site by ferry any time replacement of the jute/coir tubes is required. Without the use of a long reach excavator, only a smaller piece of equipment such as a skid steer could be utilized; this equipment would be prohibitively slow given the length of the installation and the substantial volume of the sand template.  Six-Eight Weeks Required to Replace Jute/Coir. The jute/coir are sewn together by hand at the site, which results in a lengthy construction process. Additionally, as described in the preceding bullet, the use of a long reach excavator would be required to allow reconstruction of the jute/coir from the beach level; such an excavator would need to be mobilized to the island since none are available on Nantucket. Rebuilding just under 900 feet of jute/coir would likely require approximately five weeks; this estimate includes the time required to mobilize the long reach excavator to the site. This timeframe would start once the beach had recovered enough from the storm activity that equipment could access the site. In the past, equipment access can usually occur within three days of the end of a storm; however, it has been as long as eleven days. Additionally, any storm activity during the reconstruction of the jute/coir tubes would delay reconstruction efforts, Baxter Road and Sconset Bluff 5 Alternatives Analysis Epsilon Associates, Inc. especially since such reconstruction would be occurring from the beach level. Therefore, a period of six-eight weeks or longer is considered realistic to allow the reconstruction of the jute/coir tubes (including the overlying sand template) and account for any storm delays.  Lack of Protection During Replacement of Jute/Coir. The bank would be completely unprotected from major storms when the 4th and 5th tiers need replacing. The effort to rebuild the jute/coir would take approximately six-eight weeks or longer; during this timeframe, the bank would be left partially or completely vulnerable to major storms that would result in wave run-up above the existing three tiers of geotextile tubes.  Six to Eight Week Delay in Replenishing Sand Template/ Removal of the Top of Sand Template. Any time the jute/coir need to be replaced due to degradation or depletion/failure during major storms, any remaining sand template on the top of the third tier of geotextile tubes would need to be removed. If needed, this would be accomplished using a bulldozer (for the upper portion) while a high-pressure slurry pump would be needed to spray all remaining sand off of the third tier of geotextile tubes in order to not risk tearing the top of the third tier geotube accidentally (since the top elevation of the geotextile tubes varies by about two and one half vertical feet along the length of the installation). Crucially, the top of the sand template could not be replaced until the 4th and 5th tiers of jute/coir tubes are reconstructed. If this effort is occurring post-storm, the existing sand template would likely have been quite depleted, with only minimal sand remaining in the template. Post-storm replacement of jute/coir in the winter would likely require six- eight weeks or longer, during which time all or part of the sand template would not be available. (During replacement efforts, one segment of the jute/coir tubes would be repaired and then covered with sand; then the next section would be replaced and covered with sand; this process would repeat until the entire length of the installation was completed.) In contrast, with the geotextile tube as described in Alternative Three, SBPF intends to inspect and re-grade the sand template by pushing sand from the top of the template onto the seaward face of the template (and more sand can also be added from the top of the bank via conveyor belt if needed); this effort is relatively straightforward and can be accomplished within just a few days.  Typical Construction Methods Aren’t Feasible. The methods used to fill the existing jute envelopes would not work for a longer (approximately 900-foot) project that involves a 22 cy/lf/yr sand cover. The existing jute envelopes are substantially shorter than the approximately 900-foot long installation and only involve minimal sand cover, so they are filled using a small piece of equipment known as a skid steer. For the current project, the proposed fourth and fifth jute/coir would need to be filled from below with a long-armed excavator which would be extremely Baxter Road and Sconset Bluff 6 Alternatives Analysis Epsilon Associates, Inc. arduous and subject to interruption given anticipated wave runup during winter conditions. A bulldozer or skid steer would work in tandem with the long reach excavator to rebuild the jute/coir tubes and replace the sand template. 2.1.3 Potential Benefits and Impacts The purported benefits of jute/coir are stated to be related to the slower release of sand during storm events and the associated reduction in wave energy and storm damage. A review of these potential benefits suggests that they are both negligible and not exclusively dependent upon the use of jute/coir material.  Quantity of Material Provided. A single 30’ circumference jute/coir tube can hold 1-1.5 cy of sand per linear foot; two 30’ circumference tubes would hold no more than 2.5-3 cy/lf. This material would only be available during a large storm when wave runup heights reached the elevation of the fourth or fifth tiers (this would require a storm greater than a 20-year storm). This small volume available to the littoral system from the two jute/coir tubes included in Alternative One - which would only be available during major storms - needs to be considered when evaluating the purported benefits of the use of jute/coir.  Purported Benefit of Reducing Storm Energy. It has been asserted that the use of jute/coir would provide sand continuously during a storm, and that the presence of such sand would reduce storm wave energy. During storm activity, sand can be provided, and indeed is provided, to the littoral system from offshore sand sources such as shoals, from longshore sand transport - from adjacent beaches or other eroding landforms along the eastern shore of Nantucket, and from the mitigation template (which would take a major storm to be completely exhausted). The volume of sand that would be in the water column during major storms due to inputs from these various sources (offshore shoals, longshore sand transport, and from the mitigation template itself) is at least an order of magnitude greater than the volume provided by the use of two jute/coir tubes. When considered in this context, the up to 2.5-3 cy/lf provided by two jute/coir tubes does not play a meaningful role in realizing, and is not necessary to realize, the purported benefit of reducing storm wave energy by supplying sand to the water column during storms.  Purported Benefit of Reducing Damage to Downdrift Areas. SBPF has provided information in Exhibit Z (see Section III.b) of the Request for an SOC that indicates that the mitigation sand is even more available to the littoral system than the existing coastal bank. During the March 27 storm, more sand (1.5-2.5 cy/lf) eroded from the sand template than from the jute terraces (0.25 cy/lf/yr) or unprotected bank (no or minimal erosion). This “over contribution” during small or moderate storm events can be expected to reduce damage to downdrift areas during major storms. Likewise, this regular “over contribution” can be expected to offset any limited times when the sand template has been completely exhausted; this Baxter Road and Sconset Bluff 7 Alternatives Analysis Epsilon Associates, Inc. condition is only expected be reached at the end of a major storm that occurs only every few years. (As previously stated, SBPF intends to promptly re-grade and, if necessary, replenish the sand template after any significant storm activity.) Finally, the volume of sand potentially to be contributed during a major storm that would reach the 4th and 5th tiers is a maximum of 2.5-3 cy/lf; this volume is minimal when compared to the volume of sand that can be expected to be in the littoral system during a major storm, when sand would be supplied by the up to 22 cy/lf mitigation template, longshore sand transport from adjacent areas, and offshore shoals.  Purported Benefit of Mimicking Natural Release of Sand. It has been asserted that the natural bank contributes sand continuously during a storm and that the mitigation sand needs to mimic this pattern in order to be effective. During storm activity, wave action erodes the toe of the coastal bank until such point as the upper bluff is destabilized and collapses. This pattern of gradual toe erosion followed by collapse of the upper bank may repeat itself one or more times during a given storm. Under natural conditions, then, the contribution of sand from the bank is not a continuous release of a constant volume of sand, but involves a sudden release of a large quantity of sand. This sudden release of a large quantity of sand is more closely mimicked by the sand template, which can collapse down as wave runup reaches higher elevations, than it is by the gradual release of a small volume (2.5-3 cy/lf) of sand from two jute/coir tubes.  Purported Benefit of Immediacy. It has been asserted that the use of jute/coir would allow release of sand during storms for immediate transport to and protection of downdrift areas. During major storm activity, the 2.5-3 cy/lf of sand within both jute/coir tubes would be released to the coastal environment. Some fraction of this would immediately move into the longshore transport system and some fraction would potentially move offshore, so it is likely that something less than 2.5-3 cy/lf would actually be immediately available to the littoral system.  Purported Benefit of Additional Sand Transport to the North During Storms. It has also been asserted that the use of jute/coir may specifically benefit the Quidnet Squam area, which is located to the north. Previous sediment transport studies have concluded that sand eroded from the project area tends to move both north and south depending on particular tidal and wind conditions. The potential impact of using all jute/coir for the fourth and fifth tiers of protection is that these tubes would only become exposed to wave energy during a major storm (greater than a 20-year storm). Such a major storm is likely to completely deplete the jute/coir bags, causing the bank behind the bags to fail and resulting in additional coastal bank loss. Such a storm is also likely to significantly deplete the sand template. A delay of six-eight weeks or longer would be required to completely replenish the sand template, which is a serious disadvantage since the project site is known to experience successive storms. Given this Baxter Road and Sconset Bluff 8 Alternatives Analysis Epsilon Associates, Inc. circumstance, any potential minor benefit provided by the small volume of sand contained in the jute/coir tubes is offset by the delay in re-establishing the sand template. In contrast, the sand template volume is a substantial 22 cy/lf/yr, which has been shown to be 1.5 times the average annual bank contribution rate (see Attachment A to Exhibit F of the Request for an SOC and “Responses to Comments Received on ENF for EEA 15240,” dated September 29, 2014, Response to Nantucket Land Council Comment #4). This substantial mitigation volume compensates for any minimal benefit provided by jute/coir. This finding is supported by MassDEP’s previous conclusion, in its cover letter dated December 10, 2013 that approved the Emergency Certification Request for the four tier geotextile tube system, that the increased volume of mitigation sand will mitigate any potential downdrift impacts and will address the differences between geotextile and coir/jute tubes: The implementation of the nourishment plan will mitigate any potential difference in down drift impacts between the four Geotube design and the hybrid design approved in the Town's Certification. 2.1.4 Conclusions In summary, Alternative One would result in depletion or failure of the jute/coir tubes during major storms, followed by additional failure and collapse of the upper bluff. Alternative One does not provide the required level of protection, which renders this alternative infeasible because the project area does not have the capacity to absorb additional bank loss. Additionally, construction and maintenance of Alternative One would be problematic, as it is likely that the jute/coir materials cannot support the required equipment loading and shear stresses necessary to spread the substantial volume of the sand template. Subsequent reconstruction of jute/coir would require removal of the sand template and would result in delays of six-eight weeks or longer in re-establishment of the sand template while the jute/coir tubes were rebuilt. Further, the purported benefits of the use of jute/coir tubes are minimal and are compensated for by the substantial mitigation volume of 22 cy/lf/yr. Any small benefit offered by this volume is strongly offset by the certain failure of the bank during major storm events. For all these reasons, the use of coir/jute for the fourth and fifth tiers of protection continues to be considered infeasible. 2.2 Alternative Two: Geotextile Tube Combined with Jute or Coir Tubes In this alternative, the upper tiers would include a geotextile tube to provide the required protection, combined with jute/coir tubes. Various configurations of a geotextile and jute/coir combination were evaluated. It was determined to reduce the size of the geotextile tube from 45-foot circumference to 30-foot circumference to allow the use of a Baxter Road and Sconset Bluff 9 Alternatives Analysis Epsilon Associates, Inc. larger jute/coir tube.1 Alternative Two contemplates having the fourth tier consist of a 30- foot circumference geotextile tube fronted by a 15-foot circumference jute/coir tube, and topped by a fifth tier consisting of a 30-foot circumference jute/coir tube (see attached drawing SK-02). The fifth tier is needed to reach the design height along the entire installation, in addition to allowing for additional use of jute/coir. Each 30-foot circumference tube (whether geotextile, jute, or coir) would have an approximate height of 3.5 feet. 2.2.1 Ability to Provide Required Protection By including a geotextile tube at its landward side, this alternative would generally provide a greater level of protection than Alternative One, although, as noted above, the geotextile tube alone would not reach the design elevation along the entire installation. Given its 30- foot circumference, it would also provide substantially less horizontal depth than the 45- foot geotextile tube in Alternative Three. The jute/coir tubes on the 4th and 5th tiers would be expected to fail during major storms and the geotextile tube would not fully provide protection to the 100-year storm elevation. Alternative Two therefore would fall short of providing the full required protection. 2.2.2 Ability to be Constructed and Maintained As detailed above in Section 2.1.2, construction and maintenance of jute or coir materials poses significant concerns related to the ability to drive heavy equipment on the materials, the length of time required to replace the jute/coir, and the required removal or inability to replace the sand template for a period of six-eight weeks any time the jute/coir are required to be replaced. These concerns are detailed below:  Jute/Coir Subject to Degradation. See discussion in Section 2.1.2 above.  Jute/Coir May Not Support Required Equipment Loading; Special Equipment Required. See discussion in Section 2.1.2 above.  Six-Eight Weeks Required to Replace Jute/Coir. See discussion in Section 2.1.2 above.  Six to Eight Week Delay in Replenishing Sand Template/ Removal of the Top of Sand Template. Any time the jute/coir tubes need to be replaced due to degradation or depletion/failure during major storms, any remaining sand template 1 If a 45-foot circumference geotextile tube were used, there would only be enough room to fit in a 15-foot circumference jute/coir tube in front of it. (The 45-foot geotextile tube could not be moved farther landward without cutting into the bank.) While viable from a design perspective, this concept was considered to only provide minimal incorporation of jute/coir and so was not considered further for this alternative. Baxter Road and Sconset Bluff 10 Alternatives Analysis Epsilon Associates, Inc. on the fourth tier of geotextile tube and on the seaward side of the third tier of geotextile tubes would need to be removed. If needed, this would be accomplished using a bulldozer (for the upper portion of the sand template) and a high-pressure slurry pump, which will be needed to spray all remaining sand off of the third and fourth tiers of geotextile tubes. Crucially, the top of the sand template could not be replaced until the 4th and 5th tiers of jute/coir tubes are reconstructed. If this effort is occurring post-storm, the existing sand template would likely have been quite depleted, with only minimal sand remaining in the template. Post-storm replacement of jute/coir in the winter would likely require six-eight weeks or longer, during which time all or part of the sand template would not be available. (During replacement efforts, one segment of the jute/coir tubes would be repaired and then covered with sand; then the next section would be replaced and covered with sand; this process would repeat until the entire length of the installation was completed.) In contrast, with the geotextile tube as described in Alternative Three, SBPF intends to inspect and re-grade the sand template by pushing sand from the top of the template onto the seaward face of the template (and more sand can also be added from the top of the bank via conveyor belt if needed); this effort is relatively straightforward and can be accomplished within just a few days. Additionally, the sand template which sits on top of the geotubes is never completely depleted except in the most extreme storms, allowing it to serve almost perpetually as a work platform for heavy equipment as needed.  Typical Construction Methods Aren’t Feasible. See discussion in Section 2.1.2 above. 2.2.3 Potential Benefits and Impacts The proposed use of the geotextile tube landward of the jute/coir tubes should provide adequate protection during most conditions, but not during a 100 year storm when the existing natural bank would suffer losses. Moreover, the purported benefits of jute/coir have been reviewed in detail in Section 2.1.3 above and were determined to be negligible and not exclusively dependent upon the use of jute/coir material.  Quantity of Material Provided. The 15’ circumference jute/coir tube can hold less than 0.6 cy/lf of sand; the 30’ circumference jute/coir tube can hold a 1 -1.5 cy of sand per linear foot. In total, Alternative Two would provide approximately 2 cy/lf of sand inside jute/coir tubes. This material would only be available during a large storm when wave runup heights reached the elevation of the fourth or fifth tiers (this would require a storm greater than a 20-year storm).  Purported Benefit of Reducing Storm Energy. See above discussion in Section 2.1.3.  Purported Benefit of Reducing Damage to Downdrift Areas. See above discussion in Section 2.1.3. Baxter Road and Sconset Bluff 11 Alternatives Analysis Epsilon Associates, Inc.  Purported Benefit of Mimicking Natural Release of Sand. See above discussion in Section 2.1.3.  Purported Benefit of Immediacy. See above discussion in Section 2.1.3.  Purported Benefit of Additional Sand Transport to the North During Storms. See above discussion in Section 2.1.3. The potential impact of using jute/coir for part of the fourth tier and the fifth tier of protection is that these tubes would only become exposed to wave energy during a major storm (greater than a 20-year storm). Such a major storm is likely to completely deplete the jute/coir bags, and to significantly deplete the sand template. A delay of six-eight weeks or longer would be required to completely replenish the sand template, which is a serious disadvantage since the project site is known to experience successive storms. Given this circumstance, any potential minor benefit provided by the small volume of sand (~2 cy/lf/yr) contained in the jute/coir tubes is offset by the delay in re-establishing the sand template. In contrast, the sand template volume is a substantial 22 cy/lf/yr, which has been shown to be 1.5 times the average annual bank contribution rate (see Attachment A to Exhibit F of the Request for an SOC and “Responses to Comments Received on ENF for EEA 15240,” dated September 29, 2014, Response to Nantucket Land Council Comment #4). This substantial mitigation volume compensates for any minimal benefit provided by jute/coir. This finding is supported by MassDEP’s previous conclusion, in its cover letter dated December 10, 2013 that approved the Emergency Certification Request for the four tier geotextile tube system, that the increased volume of mitigation sand will mitigate any potential downdrift impacts and will address the differences between geotextile and coir/jute tubes: The implementation of the nourishment plan will mitigate any potential difference in down drift impacts between the four Geotube design and the hybrid design approved in the Town's Certification. 2.2.4 Conclusions In summary, Alternative Two is preferable to Alternative One, but does not fully provide the required level of protection. Construction and maintenance of Alternative Two would be both problematic and burdensome, as regular replacement of the jute/coir would be required. Such replacement would require six-eight weeks or more and the use of special (off-island) equipment, since the jute/coir materials cannot support the required equipment loading and shear stresses necessary to spread the substantial volume of the sand template. During this six-eight week timeframe, all or part of the sand template would not be available to the littoral system. The delay in replenishing the sand template is a substantial disadvantage, especially compared to the small volume (2 cy/lf) provided by the use of jute/coir. Further, the purported benefits of the use of jute/coir have been shown to be both Baxter Road and Sconset Bluff 12 Alternatives Analysis Epsilon Associates, Inc. minimal and compensated for by the substantial mitigation volume. For all the preceding reasons, Alternative Two is not recommended. 2.3 Alternative Three: Geotextile Tube In this alternative, the fourth tier would consist of a single 45-foot circumference geotextile tube. The design elevation would be reached along the length of the entire installation (see attached drawing SK-03). 2.3.1 Ability to Provide Required Protection This alternative would provide the required protection, along the entire length of the installation, from a 100-year storm. 2.3.2 Ability to be Constructed and Maintained One-time, temporary removal of the top of the sand template would be required; however, this work could probably be scheduled in the summer when it is unlikely that the sand template would be contributed to the littoral system. The geotextile tubes can support the required equipment loading and shear stresses associated with the heavy equipment needed to spread the sand template. Unlike the jute/coir material, no regular repair, replacement, or maintenance of the geotextile tube is anticipated. Occasional post-storm repairs may be required in discreet locations. 2.3.3 Potential Benefits and Impacts The fourth-tier geotextile tube, with its substantial sand cover of 22 cy/lf, is expected to avoid adverse impacts to downdrift areas. (Sections 2.1.3 and 2.2.3 above describe how the purported benefits associated jute/coir are negligible.) This amount is equivalent to 1.5 times the average bank contribution amount (see Attachment A to Exhibit F of the Request for an SOC and “Responses to Comments Received on ENF for EEA 15240,” dated September 29, 2014, Response to Nantucket Land Council Comment #4). No regular or lengthy removal of the sand template would be required for ongoing maintenance of the geotextile tubes. Likewise, no regular use of heavy equipment on the beach for maintenance is anticipated. Finally, there would be no increase in wave reflection compared to the use of jute/coir. This is because, at the higher elevations of the fourth and/or fifth tiers, the impacts are from wave runup and not from direct wave attack. As such, wave reflection would be expected to be negligible for either material (geotextile or jute/coir). 2.3.4 Conclusions In summary, Alternative Three is preferred because it would provide the required protection for the project area while also maintaining the sand supply to the littoral system. The geotextile tubes can support the required equipment loading and shear stresses associated Baxter Road and Sconset Bluff 13 Alternatives Analysis Epsilon Associates, Inc. with the heavy equipment needed to spread the sand template. Alternative Three does not require regular intensive maintenance, and does not involve delays of six-eight weeks or longer to rebuild any jute/coir tubes and replace the entire sand template. The benefits of jute/coir have been shown to be minimal and are mitigated by the substantial sand template volume of 22 cy/lf. Therefore, Alternative Three is preferred. Baxter Road and Sconset Bluff 14 Alternatives Analysis Epsilon Associates, Inc. 3.0 ALTERNATIVE DESIGNS FOR THE RETURNS The Secretary directed that the project look at design alternatives for the returns, in accordance with the comment letter received from the Massachusetts Office of Coastal Zone Management (CZM). This comment reads: [CZM] recommends that the proponent use alternative methods for reducing end scour that would reflect less wave energy than the proposed 15’ circumference geotextile tubes. In order to mitigate the end scour and avoid extending it onto adjacent areas, CZM typically recommends that softer options that reflect less wave energy be considered (e.g. sand-filled coir bags and nourishment). The end scour protection should also taper in elevation and slope to minimize the amount of reflected wave energy and the amount of associated erosion. In accordance with this comment and the direction in the Secretary’s Certificate, SBPF and its engineering consultant, OCC, developed three proposed alternative return design concepts that would reduce the amount of reflected wave energy. Each alternative design concept is discussed below. As in Section 2.0 above, alternatives are evaluated according to the Wetlands Protection Act Regulations as listed in Section 310 CMR 10.30(3)(a): “a coastal engineering structure or a modification thereto shall be designed and constructed so as to minimize, using best available measures, adverse effects on adjacent or nearby coastal beaches due to changes in wave action….” “Best Available Measures” are defined in 310 CMR 10.04 as: “the most up-to-date technology or the best designs, measures or engineering practices that have been developed and that are commercially available.” These standards make it clear that coastal engineering structures (including returns) should minimize adverse effects on adjacent beaches by using the best engineering practices and designs. 3.1 Original Return Design: Twenty 15-foot Circumference Geotextile Tubes The original return design (see attached drawing SK-04) included twenty geotextile tubes, each 15-foot in circumference. The geotextile tubes were to be placed in a stacked design, extending from elevation +3 or +4 MLW up to the level of the top of the fourth geotextile tube at +26 to +28 MLW. The original design incorporated several features to reduce wave reflectivity and end scour. Specifically, the proposed design utilized smaller geotextile tubes where the lower tiers were in a somewhat stepped configuration, which would result in decreased wave reflectivity as compared to the use of larger (45-foot circumference) geotextile tubes in a more vertical configuration. It was not anticipated that this design would result in end scour; however, three alternative return concepts have been developed in order to be responsive to the comments received from CZM. Baxter Road and Sconset Bluff 15 Alternatives Analysis Epsilon Associates, Inc. 3.2 Alternative Return Concept One: Six 30-Foot Circumference Geotextile Tubes Alternative Return Concept One includes six 30-foot circumference geotextile tubes (see attached drawing SK-05). Each geotextile tube is approximately 4 to 5 feet in height and 13 feet in width. The geotextile tubes are placed in a stepped configuration from elevation +3 or +4 MLW to elevation ~+24 to +26 MLW. The slope is approximately half as steep as in the Original Return Design. The 30-foot circumference size was selected after discussion with the manufacturer, where it was determined that the use of 15-foot circumference tubes was not advisable because it would result in less stable fill proportions. Per the manufacturer’s recommendations, the geotextile tubes for the returns are placed in alignment with the main geotextile tube structure: the top of the lowest tier of the return aligns with the top of the lowest tier of the main installation; the top of the third tier of the return aligns with the top of the second tier of the main installation; and the top of the fifth tier of the return aligns with the top of the third tier of the main installation. Following this approach, the sixth (and top) tier of the returns will be somewhat lower in elevation than the main installation. Accordingly, Alternative Return Concept One achieves both a shallower slope and a reduced elevation compared to the Original Return Design, both of which will decrease wave reflectivity. The option of further tapering the height of the return was investigated; however, this option would require using shorter geotextile tubes for the top tiers of the returns. Given their smaller (30-foot circumference) size, these shorter geotextile tubes would not be stable in a high energy environment like Sconset and could potentially be mobilized during storm events, becoming a source of marine debris. Therefore, this variation that involved using shorter tubes was not evaluated further. In summary, Alternative Return Concept One utilizes 30-foot circumference geotextile tubes and would provide the required protection during storm activity. This alternative reduces the number of geotextile tubes required for the returns, achieves a shallower slope, and results in a reduced elevation. All these factors will result in reduced wave reflectivity. 3.3 Alternative Return Concept Two: Returns Constructed of Jute/Coir In this alternative, the same size and configuration of tubes as Alternative Return Concept One (six tiers of 30-foot circumference geotextile tubes) would be selected given its noted benefits in reducing wave reflectivity compared to the Original Design. However, in Alternative Return Concept Two, all or part (the top three tiers) of the six tiers of 30-foot circumference tubes would be constructed out of jute/coir. Either approach (use of jute/coir for all of the returns, or for just the top half of the returns) would have similar considerations, and so both options are evaluated together below. Alternative Return Concept Two would not be expected to provide the required level of protection during major storms. As noted above in Section 2.1.1, jute or coir cannot withstand the storm forces regularly experienced at the site. Jute or coir would be expected Baxter Road and Sconset Bluff 16 Alternatives Analysis Epsilon Associates, Inc. to fail during major, multi-day, or successive storms, leaving the main installation subject to flanking and end scour. As noted above in Section 2.1.2, the use of jute or coir for all or part of the returns would be problematic and disadvantageous. The jute or coir would be anticipated to require regular replacement, probably every one-three years. Rebuilding the returns would require two-three weeks; during this timeframe; the ends of the installation would be completely or partially unprotected. This is considered a serious disadvantage, as successive storms are known to occur at the project site. The jute/coir could not support the required equipment loading and shear stresses, so special equipment would need to be brought on-island or only smaller equipment (such as a skid steer) could be used to rebuild the returns. This option would also cause serious obstruction to the spreading of the sand template. Given its substantial volume, the sand template is typically spread by heavy equipment (excavator and/or bulldozer) that access the main installation by sand ramps placed over the returns. The use of jute/coir for all or part of the returns would likely remove this source of access for the heavy equipment, requiring the use of special or smaller equipment and resulting in long delays in replacing the sand template after storms. Further, the use of jute/coir in Alternative Return Concept Two may not have a meaningfully different wave reflectivity compared to Alternative Return Concept One, since both involve the same slope and geometry. In summary, Alternative Return Concept Two would not provide the required level of protection. Alternative Return Concept Two would also require regular and time- consuming replacement of the returns, which would leave the ends of the installation vulnerable to flanking and end scour during successive, multi-day, or major storms. Further, Alternative Return Concept Two would obstruct and delay the replacement of the sand template. Finally, Alternative Return Concept Two may not have a meaningful difference in wave reflectivity compared to Alternative Return Concept One. For these reasons, Alternative Return Concept Two is rejected. 3.4 Alternative Return Concept Three: Gabions or Rip Rap Alternative Return Concept Three is a preliminary concept that considers the use of gabions (HDPE baskets that are approximately four feet high x five feet wide x ten feet long and are filled with 4- to 6 –inch stone) or rip rap for the returns. Given the porous nature of gabions or rip rap, either of these materials would be expected to have the lowest wave reflectivity compared to the Original Design, Alternative Return Concept One, and Alternative Return Concept Two. Additionally, given their modular nature, the gabions or the rip rap likely could taper in height from where they abut the main geotextile tube structure down to their ends. The gabion or rip rap returns would likely provide the required level of protection; however, design considerations would include (1) ensuring that suitable backfill could be placed and compacted to support the gabions or rip rap, and (2) ensuring that shifts in the rip rap or gabion returns during storms would not damage or puncture the adjacent geotextile tubes, likely through “shrouding” the geotextile tubes by placing an additional layer of geotextile material over the existing geotextile tubes to provide additional tear Baxter Road and Sconset Bluff 17 Alternatives Analysis Epsilon Associates, Inc. protection. Because SBPF believes opponents of the project would use any proposal for rock-filled gabions or rip rap as an occasion for unwarranted controversy and extended objection, and due to the previously mentioned design considerations, Alternative Return Concept Three is not considered further at this point. If MassDEP prefers this alternative SBPF is prepared to provide further design details and parameters. 3.5 Conclusions Alternative Return Concept One is preferred because it would provide the required protection during storm activity and also reduces the number of geotextile tubes required for the returns, achieves a shallower slope( the slope is reduced to approximately half of the slope in the Original Design), and results in a reduced elevation. Alternative Return Concept One is also responsive to the comments received from CZM because the shallower slope and reduced height would reduce wave reflection and associated erosion. Finally, Alternative Return Concept One would not require frequent replacement and can support the anticipated equipment loads required to spread the sand template in a timely fashion. The Original Design is no longer recommended because it involves a steeper slope than Alternative Return Concept One, is less stable than Alternative Return Concept One, and involves the use of more geotextile tubes (twenty for the Original Design vs. six for Alternative Return Concept One). Alternative Return Concept Two is rejected because it would not provide the required level of protection and cannot support the required equipment loads, as heavy equipment needs to traverse sand ramps constructed on top of the returns in order to spread the substantial volume of the sand template along the main installation. Alternative Return Concept Two also results in increased vulnerability of the ends to flanking and scour during major, successive, or multi-day storms that would be expected to deplete any jute/coir bags and would subsequently require two-three weeks for reconstruction. Alternative Return Concept Three was reviewed to show that the use of rip rap or rock-filled gabions may result in the greatest reduction in wave reflectivity. Because SBPF believes opponents of the project would use any proposal for rock-filled gabions or riprap as an occasion for unwarranted controversy and extended objection, and due to design considerations that highlight the complexity of using different materials for the returns than for the main installation, Alternative Return Concept Three is not considered further at this point. Attachment M DEP Superseding Order of Conditions (dated December 19, 2014) Attachment N Final Order of Conditions (SE48-2824) (dated September 30, 2015) Attachment O Memorandum of Understanding (MOU) Between the Town of Nantucket and SBPF (dated July 5, 2013) and Amendment to the MOU (dated October 9, 2013) Attachment P Emergency Status for Homes and Public Infrastructure Along Baxter Road, Nantucket, MA (dated November 25, 2013) M E M O R A N D U M Date: November 25, 2013 To: Joshua Posner, President, Sconset Beach Preservation Fund From: Maria Hartnett and Les Smith, Epsilon Associates, Inc. Subject: Emergency Status for Homes and Public Infrastructure Along Baxter Road, Nantucket, MA This memo defines those properties within the “Baxter Road Temporary Stabilization” project area (DEP File No. 048-2610) from 85-107A Baxter Road that require protection under an Emergency Certification. This analysis is based upon existing distances from the top of the coastal bank to homes and Baxter Road, the long-term erosion rate, and the maximum anticipated winter erosion rate (based on actual top of bank loss during the 2012-2013 winter season). Existing Conditions Existing Conditions at Sconset are presented on Figures 1 and 2. Figure 1 is an oblique aerial photo taken in June 2013; the distances presented on Figure 1 are based on May 30, 2013 field measurements of the minimum distances between the top of the coastal bank and existing homes and Baxter Road. Figure 2 is an aerial photo taken in July 2013 with transects spaced every 20 feet that list the distance between the edge of Baxter Road and the top of the coastal bank. To develop this figure, GIS was utilized to digitize the eastern edge of pavement for Baxter Road and the 2013 top of coastal bank line, and then to generate the 20 foot transects with listed distances. These figures demonstrate the following: o The homes at 93 and 97 Baxter Road are between 8 and 24 feet from the edge of the bluff. o The distance from the edge of Baxter Road to the top of the bluff for the vacant lots at 91, 99, 101, and 105 Baxter Road is as little as 29 feet and averages approximately 50.6 feet (Table 1). This distance gradually starts to increase south of 91 Baxter Road. Potential Threat from Erosion We have previously determined the long-term erosion rate for the area from 85-107A Baxter Road as 4.6 feet/year, in a memo from Epsilon Associates dated November 1, 2013. Given the significant bank losses that occurred during the winter of 2012-2013, we also recommend the consideration of potential single-season coastal bank loss at Sconset when determining those properties that require immediate protection. As previously mentioned, the winter of 2012-2013 resulted in significant coastal bank erosion at Sconset. An analysis of the erosion that occurred between 2012-2013 was conducted by digitizing top of bank lines from 2012 and 2013 aerial photographs (Figure 3) and then calculating retreat distances along shore-perpendicular transects spaced every 20 feet. This analysis indicates that the average erosion in the area from 85-107A was 20 feet and ranged up to 40 feet (Table 2). Criteria for Defining an “Emergency” It is our opinion that the situation at Sconset constitutes an emergency, and that all properties and public infrastructure that may be lost due to erosion during the next few winter months require immediate protection. The above analysis of 2012-2013 erosion demonstrates that up to 40 feet of coastal bank can be lost during a single winter; this distance represents the basis of the below criteria for those homes and sections of roadway that require immediate protection. o Emergency Criteria for Homes. All homes within 40 feet of the top of the coastal bank require immediate protection. o Emergency Criteria for Public Infrastructure (Baxter Road). All sections of Baxter Road within 65 feet of the top of the coastal bank require immediate protection. This distance is based upon the sum of the potential single-season erosion (40 feet) plus the minimum distance of 25 feet that needs to be maintained seaward of the Baxter Road pavement for structural stability. This 25 foot distance is based upon information presented in the November 8, 2013 letter from Milone & MacBroom. After conferring with the well- respected geotechnical firm Haley & Aldrich, Milone & MacBroom reported that “[t]he town can maintain travel on Baxter Road until such time as the top of the bluff is 25 feet or less from the edge of pavement. When the top of the bluff is within 25 feet of the pavement edge, the road should be closed to traffic until a detailed assessment can be completed by a geotechnical engineer.” Utilizing the above criteria to define which portions of 85-107A Baxter Road require immediate protection yields the following conclusions: o Homes Requiring Immediate Protection. The pre-1978 homes located at 93 and 97 Baxter Road require immediate protection. o Sections of Baxter Road Requiring Immediate Protection. The sections of Baxter Road along the southern two-thirds of 105 Baxter Road, 101 Baxter Road, 99 Baxter Road, and 91 Baxter Road require immediate protection. (In limited parts of 91 Baxter Road, the distance between the edge of pavement and top of the bluff is just over 65 feet. We recommend providing protection across 91 Baxter its entirety to avoid discontinuous protection and/or end effects.) We also note that the adjacent lot at 87 Baxter Road has a small section where the distance between the top of the bluff and edge of pavement are less than 65-feet. Protection for 87 Baxter Road could also be provided if this can be accomplished without compromising the ability to protect the more threatened areas from 91-105 Baxter Road during the limited time available before the winter storm season. Finally, we note that Baxter Road provides access to pre-1978 homes both on its seaward and landward sides, and that protecting Baxter Road is critical to maintain access to the pre-1978 homes on the landward side of Baxter Road adjacent to 91, 99, 101, and 105 Baxter Road. Figure 1 Existing Conditions - 91 to 109 Baxter Road Setbacks based on 5/31/2013 on-the-ground measurements and July 2013 aerial photo Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA Lot 99 Lot 101 Lot 105 44’-60’ road setback 37-45’ road setback 29’-50’ road setback Lot 93 Lot 97 Lot 91 Lot 107 Lot 107A Lot 109 17’ shed setback 24’ house setback 8’ house setback Note: “Lot” label refers to street numbers. Photo Date: June 2013 102 679995911049999997697969695949391898710686103851031028382.6182.5982100817876757575 747373737271 70 69 68 68 67 6767 66 66 65 65 64 63 6363 62 6160 6058 57 57 5754 43 54 54 41 52 5050504646 4544 43 43 43 42 4241 4037 66 99 97 87 85 101 105 109 93 91 117 115 113 107 119 107A G:\Projects\Lighthouse\2013\Geotube\Revised\transects_117-87.mxd Figure 2Geotube Analysis Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, Massachusetts LEGEND Basemap: 2013 Aerial Imagery, Col-East, Inc. Edge of Pavement 2013 Top of Bank Transects (feet) Parcels 0 60 12030Feet1 inch = 120 feetScale1:1,440 BA X T ER RO AD BAXTER ROADSANKATY ROAD 85 99 97 87 101 83 105 109 93 91 107 81 107A 113 Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP,swisstopo, and the GIS User Community G:\Projects\Lighthouse\2013\ConCom\Retreat\Revised\Detailed_Analysis_v3\2012-2013.mxd Baxter Road and Sconset Bluff Storm Damage Prevention Project Nantucket, MA Coastal Bank Retreat LEGEND Basemap: 2013 Aerial Imagery, Col-East, Inc. 2012 Top of Coastal Bank 2013 Top of Coastal Bank Parcel Boundary °0 60 12030Feet1 inch = 120 feetScale1:1,440 Transect Lot Distance from EOP to 2013 TOB (ft) 37 105 63 38 105 50 39 105 46 40 105 43 41 105 41 42 105 42 43 101 41 44 101 42 45 101 43 46 101 43 47 101 45 48 101 44 49 101 40 50 101 37 51 101 43 52 101 46 53 99 54 54 99 52 55 99 50 56 99 50 57 99 54 58 99 57 59 99 54 60 99 57 61 99 60 75 91 67 76 91 69 77 91 63 78 91 57 79 91 67 Average 50.6 Table 1. Distance from Edge of Pavement to Top of Coastal Bank, 91, 99, 101, and 105 Baxter Road, Nantucket, MA Table 1. 2012-2013 Retreat Distances for 85-107A Baxter Road, Nantucket, MA Transect ID Street Number 2012-2013 Retreat (ft) 30 107A 22.1 31 107A 22.6 32 107A 25.9 33 107 24.4 34 107 27.2 35 107 18.6 36 107 20.6 37 107 22.0 38 105 16.9 39 105 10.5 40 105 17.5 41 105 33.2 42 105 27.3 43 105 25.2 44 105 25.0 45 105 24.5 46 105 21.8 47 101 25.2 48 101 17.1 49 101 21.5 50 101 18.6 51 101 13.9 52 101 18.9 53 101 25.2 54 101 23.6 55 101 17.0 56 Public Access 18.9 57 99 16.6 58 99 23.6 59 99 22.4 60 99 26.4 61 99 19.1 62 99 17.2 63 99 19.6 64 99 15.3 65 99 22.5 66 97 23.5 67 97 20.5 68 97 19.0 69 97 25.0 70 97 27.4 71 97 22.4 72 97 23.5 Transect ID Street Number 2012-2013 Retreat (ft) 73 97 26.8 74 93 25.6 75 93 11.5 76 93 8.1 77 93 16.5 78 93 20.0 79 91 16.4 80 91 6.1 81 91 7.5 82 91 20.5 83 87 13.2 84 87 22.8 85 87 22.1 86 87 27.2 87 87 40.1 88 87 38.2 89 87 18.7 90 87 11.4 91 85 18.2 92 85 11.2 93 85 11.4 94 85 15.4 95 85 5.8 96 85 21.5 97 85 17.4 98 85 17.3 99 85 13.1 100 85 16.2 101 85 23.7 102 85 25.7 103 85 24.9 Average Retreat 20.3 Maximum Retreat 40.1 Attachment Q Property Ownership and Abutter Information Property Address Map & Parcel Record Title Holder Assessed Owner Recording information 59 Baxter Road 49-20 Kevin F. Dale, Trustee of 59 Canopache Nominee Trust Kevin F. Dale, Trustee of 59 Canopache Nominee Trust C19072 61 Baxter Road 49-21 Ann R. Healey, Trustee of the Mayflower QPRT Ann R. Healey, Trustee of the Mayflower QPRT 1325/277 63 Baxter Road 49-22 Elizabeth Singer, Trustee of the 64 Baxter Road Realty Trust Elizabeth Singer, Trustee of the 64 Baxter Road Realty Trust C19844 65 Baxter Road 49-23 Thomas Tuttle & Sharmila Tuttle Thomas Tuttle & Sharmila Tuttle 1200/102 67 Baxter Road 49-24 Morning Light LLC, Margaret Hearst manager Morning Light LLC, Margaret Hearst manager 845/269 69 Baxter Road 49-25 Richard & Marianne L. Moscicki Richard & Marianne L. Moscicki 1294/117 71 Baxter Road 49-26.1 John C. Merson and Carol Bunevich John C. Merson and Carol Bunevich C21251 73 Baxter Road 49-27 Christian M. Darby Christian M. Darby 1315/310 75 Baxter Road 49-30 Sankaty Bluff Group, LLC, John E. Osborn and Deborah P. Osborn manager Sankaty Bluff Group, LLC, John E. Osborn and Deborah P. Osborn manager 1152/78 77 Baxter Road 49-31 Joshua Posner and Eileen Rudden Joshua C. Posner and Eileen M. Rudden C17538 79 Baxter Road 49-32 Helmut F. Weymar & Caroline S. Weymar F. Helmut Weymar & Caroline S. Weymar C12804 81 Baxter Road 49-33 William D. & Deborah Futter Cohan William D. & Deborah Futter Cohan C23689 83 Baxter Road 49-34 Marie Dostalier and Richard Touchette Marie Dostalier and Richard Touchette C23698 85 Baxter Road 49-35 Siasconset Preservation Fund, Inc. - Joshua Posner President Siasconset Preservation Fund, Inc. - Joshua Posner President C26035 87 Baxter Road 49-8 Samuel Furrow & Ann Furrow Samuel Furrow & Ann Furrow 839/295 91 Baxter Road 48-22 Daniel L. Korengold, Trustee of D&M Baxter Road Nominee Trust Daniel L. Korengold, Trustee of D&M Baxter Road Nominee Trust 1352/45 93 Baxter Road 48-21 Steven T. & Erin P. Freeman Steven T. & Erin P. Freeman 1069/97 97 Baxter Road 48-19 Lawrence C. & Margaret McQuade Lawrence C. & Margaret McQuade C17087 99 Baxter Road 48-18 Ann B. Furrow Ann B. Furrow C20681 101 Baxter Road 48-17 101 Baxter Road LLC, James E. Walker and Deborah C. Walker managers 101 Baxter Road LLC, James E. Walker and Deborah C. Walker managers 01427/0341 105 Baxter Road 48-15 Marilee B. Matteson, as Trustee of Marilee Brill Matteson Nominee Trust Marilee B. Matteson, as Trustee of Marilee Brill Matteson Nominee Trust C25689 107 Baxter Road 48-14.1 Whitney A. Gifford, Trustee of S.C. Nominee Trust Hannah J. Gretz, Trustee of S.G. Nominee Trust 01285/0217 107A Baxter Road 48-14 Whitney A. Gifford, Trustee of S.G. Nominee Trust Whitney A. Gifford, Trustee of S.G. Nominee Trust 647/191 109 Baxter Road 48-12 Justine Mascioli Kenney, Trustee of Frederick P. Mascioli Living Trust Justine Mascioli Kenney, Trustee of Frederick P. Mascioli Living Trust C26159 113 Baxter Road 48-11 Loretta Yoder and Kyle L. Latshaw Loretta Yoder and Kyle L. Latshaw 925/147 115 Baxter Rd 48-10 115 Baxter LLC, John Khawam manager 115 Baxter LLC, John Khawam manager 1513/335 117 Baxter Rd 48-9 Stephen B. Cohen Stephen B. Cohen 575/163 119 Baxter Rd 48-7 Sconset Trust, Inc. - Elliot Gewirtz President Sconset Trust, Inc. - Elliot Gewirtz President C18718 Sconset Bluff 49-9 Town of Nantucket Town of Nantucket 102/119 Sconset Bluff 48-6 Town of Nantucket Town of Nantucket 185/52 Sconset Bluff 48-8 Town of Nantucket Town of Nantucket C1702 Sconset Bluff 48-5 Sconset Trust, Inc. - Elliot Gewirtz President Sconset Trust, Inc. - Elliot Gewirtz President Record & Assessed Owners: 59-119 Baxter Road - 2018 Notification to Abutters Under The Massachusetts Wetlands Protection Act In accordance with the second paragraph with Massachusetts General Laws Chapter 131, Section 40 you are notified of the following: 1. The name of the applicant is: Siasconset Beach Preservation Fund. 2. The applicant has filed a Notice of Intent (NOI) with the Nantucket Conservation Commission. The Project includes expansion of the existing geotextile tube project to provide storm damage protection for homes and public infrastructure along the length of Sconset bluff that is eroding. The new section of four tiers of geotextile tubes will extend north from the Existing Project to 119 Baxter Rd and south from the Existing Project to 59 Baxter Rd (plus returns), providing continuous protection from 59 to 119 Baxter Road. 3. Project activities are subject to review by the Nantucket Conservation Commission under the Massachusetts Wetlands Protection Act and Nantucket Wetlands Bylaw. 4. The address of the lot where activities are proposed is on the bluff and beach seaward of 59 to 119 Baxter Road (plus returns on 55 and 122 Baxter Road). 5. Copies of the NOI and site plans may be examined or obtained for a fee from either the: • Nantucket Conservation Commission, 2 Bathing Beach Road, Nantucket MA 02554, (508) 228-7230. Please call the Conservation Commission beforehand to verify arrangements. • Or (copies) from Epsilon Associates, Inc., 3 Mill & Main Place, Suite 250, Maynard, MA 01754, (978) 897-7100. 6. Information regarding the date, time, and place of the public hearing may be obtained from the Nantucket Conservation Commission by calling (508) 228-7230. NOTE: Notice of the public hearing, including its date, time and place, will be published at least five calendar days prior to the hearing in The Inquirer & Mirror. NOTE: You also may contact the Massachusetts Department of Environmental Protection – Southeast Regional Office (508-946-2700) for more information about this application or the Massachusetts Wetlands Protection Act. Attachment R Filing Fee Information noifeetf.doc • Wetland Fee Transmittal Form • rev. 10/11 Page 1 of 2 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands NOI Wetland Fee Transmittal Form Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 Important: When filling out forms on the computer, use only the tab key to move your cursor - do not use the return key. A. Applicant Information 1. Location of Project: 59-119 Baxter Road (plus returns) a. Street Address Nantucket b. City/Town c. Check number d. Fee amount 2. Applicant Mailing Address: Josh a. First Name Posner b. Last Name Siasconset Beach Preservation Fund (SBPF) c. Organization P.O. Box 2279 d. Mailing Address Nantucket e. City/Town MA f. State 02584 g. Zip Code h. Phone Number i. Fax Number jposner@risingtidellc.net j. Email Address 3. Property Owner (if different): a. First Name b. Last Name See attached property owners (Town of Nantucket and property owners 59 -119 Baxter Road) c. Organization d. Mailing Address e. City/Town f. State g. Zip Code h. Phone Number i. Fax Number j. Email Address To calculate filing fees, refer to the category fee list and examples in the instructions for filling out WPA Form 3 (Notice of Intent). B. Fees Fee should be calculated using the following process & worksheet. Please see Instructions before filling out worksheet. Step 1/Type of Activity: Describe each type of activity that will occur in wetland resource area and buffer zone. Step 2/Number of Activities: Identify the number of each type of activity. Step 3/Individual Activity Fee: Identify each activity fee from the six project categories listed in the instructions. Step 4/Subtotal Activity Fee: Multiply the number of activities (identified in Step 2) times the fee per category (identified in Step 3) to reach a subtotal fee amount. Note: If any of these activities are in a Riverfront Area in addition to another Resource Area or the Buffer Zone, the fee per activity should be multiplied by 1.5 and then added to the subtotal amount. Step 5/Total Project Fee: Determine the total project fee by adding the subtotal amounts from Step 4. Step 6/Fee Payments: To calculate the state share of the fee, divide the total fee in half and subtract $12.50. To calculate the city/town share of the fee, divide the total fee in half and add $12.50. noifeetf.doc • Wetland Fee Transmittal Form • rev. 10/11 Page 2 of 2 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands NOI Wetland Fee Transmittal Form Massachusetts Wetlands Protection Act M.G.L. c. 131, §40 B. Fees (continued) Step 1/Type of Activity Step 2/Number of Activities Step 3/Individual Activity Fee Step 4/Subtotal Activity Fee Category 5 - Geotextile Tubes 2,873 lf $4/lf Max = $2,000 Step 5/Total Project Fee: Step 6/Fee Payments: Total Project Fee: $2000 a. Total Fee from Step 5 State share of filing Fee: $987.50 b. 1/2 Total Fee less $12.50 City/Town share of filling Fee: $1012.50 c. 1/2 Total Fee plus $12.50 C. Submittal Requirements a.) Complete pages 1 and 2 and send with a check or money order for the state share of the fee, payable to the Commonwealth of Massachusetts. Department of Environmental Protection Box 4062 Boston, MA 02211 b.) To the Conservation Commission: Send the Notice of Intent or Abbreviated Notice of Intent; a copy of this form; and the city/town fee payment. To MassDEP Regional Office (see Instructions): Send a copy of the Notice of Intent or Abbreviated Notice of Intent; a copy of this form; and a copy of the state fee payment. (E-filers of Notices of Intent may submit these electronically.)