HomeMy WebLinkAbout20 SE48_3115 SBPF Response to Comments from 12_03_2018
PRINCIPALS
Theodore A Barten, PE
Margaret B Briggs
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
Maria B. Hartnett
ASSOCIATES
Richard M. Lampeter, INCE
Geoff Starsiak, LEED AP BD+C
Marc Bergeron, PWS, CWS
3 Mill & Main Place, Suite 250
Maynard, MA 01754
www.epsilonassociates.com
978 897 7100
FAX 978 897 0099
21597/2018/Expanded Project/NOI/Public Hearing Comments
January 4, 2019
Nantucket Conservation Commission Via Electronic Mail and U.S. Mail
2 Bathing Beach Road
Nantucket, MA 02554
Subject: Response to Comments from the December 3, 2018 Hearing on the
Expanded Baxter Road and Sconset Bluff Storm Damage Prevention
Project (DEP File No. SE 48-3115)
Dear Commission Members:
On behalf of the Sconset Beach Preservation Fund (“SBPF”), Epsilon Associates, Inc.
(“Epsilon”) submits additional information to questions raised by Nantucket
Conservation Commission Members and public comments during the Nantucket
Conservation Commission (“Commission”) December 3, 2018 Public Hearing for
the Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project
(“Expanded Project”). These written responses provide additional information to
augment verbal responses made by SBPF team members during the Public Hearing,
as applicable. Many of the questions raised have been answered on numerous
previous occasions and therefore many of the responses here reference those
previous responses.
Commission Questions
1. Volume of Sand Contributed from the Sconset Coastal Bank -- The volume
of sand contributed from the Sconset Coastal Bank was calculated in accordance
with the method accepted by the Massachusetts Department of Environmental
Protection (“MassDEP”) and the Massachusetts Office of Coastal Zone Management
(“CZM”). The sand contribution volume, and the corresponding sand mitigation
volume, was presented in Notice of Intent (“NOI”) Section 2.3, discussed in the
correspondence to the Commisison dated November 2, 2018, and was presented to
the Commission during the November 5, 2018 Public Hearing. See November 5,
2018 presentation slides 47 – 50.
Nantucket Conservation Commission 2
January 4, 2019
2. Sand Template Management – The proposed adaptive sand management
program is presented in the Secton 4.2 of the NOI and further refined in the
Template Sand Replenishment Protocol submitted to the Commission in
correspondence dated November 2, 2018, and was discussed with the Commisison
at the November 5, 2018 Public Hearing. See November 5, 2018 presentation
slides 7, 8 and 9.
3. Potential Geotube Redesign – The proposed four tier geotube design for the
Expanded Project extends the existing four tier design north and south. The
proposed design was developed using extensive modeling as detailed by Gordon
Thomson at the October 1, 2018 Public Hearing. See October 1, 2018 presentation
slides 12 – 27. No re-design is proposed. Commission members suggested a
design change that would either remove the fourth geotube tier or replace the fourth
geotube tier with coir logs / envelope system. The fourth geotbe tier is needed for
the long-term effectiveness and stability of the geotube system, as discussed during
the October 1, 2018 Public Hearing.
Coir logs installed on top of the geotube system will not result in an effective
system that complies with accepted engineering practice. Coir logs need to be
anchored into the underlying substrate, typically with anchors or stakes. Anchoring
or staking coir logs in to the geotubes would damage the geotube. Therefore, coir
logs are not proposed to be installed on top of the geotubes. In addition, the use
the needed sand moving equiptment to re-cover geotubes, after storms wash away
sand, could not be used on top of coir envelopes because the equipment would
damage the coir logs.
That said, overtime it is expected that the returns will need to be extended as the
unprotected Coastal Bank abutting the geotube returns continues to erode as it has
over the recent decade. The project is providing sand to address sediment that
would have been provided to the littorral drift system from recession of the bluff in
front of the geotube system, but not for natural background losses that will still
occur elsewhere along the exposed shoreline. We expect that coir return
extensions, similar in design to those recently approved by the Commisison for the
existing Project as an Amended Order of Conditons (“OOC”) (SE 48-2824), would
be appropriate in the future to fill that gap. We therefore request that a Special
Condition be included in the OOC for this Expanded Project (SE48-3115) that
would allow installation of coir return extensions in the future, when needed.
4. Public Access to the Beach Across the Geotube System – The Applicant will
work with the Commisison to provide pedestrian access down the Coastal Bank and
Nantucket Conservation Commission 3
January 4, 2019
down the face of the geotube system. Most likely the method will be the
installation of a combination of permanent and seasonal stairs / gang-ways as
mentioned during the December 3, 2018 Public Hearing. The Applicant can
provide revised drawing showing location of stairs as a specicial condition to an
OOC.
5. Status of Homes as Pre-1978 Homes – The Applicant has reviewed the
status of homes on the east side of Baxter Road regarding the ability to protect them
as pre-1978 structrures pursuant to the Massachusetts Wetlands Protection Act
(“Act”) and the Nantucket Wetlands Protection By Law (“Bylaw”). That review
included renovations to the homes based on Building Department files. See
correspence to the Commission dated November 2, 2018 (Attachment 2 to the
November 2, 2018 correspondence) and November 16, 2018 (Attachment 2 to the
November 16, 2018 correspondence).
During the December 3, 2018 Public Hearing, Commisisoner Golding specifically
cited changes at 77 Baxter Road, which he said makes structures on this lot
ineligible for protection as a pre-1978 structures pursuant to the Bylaw. Please note,
changes at that property included demolition of a 500 square foot (sf) bunkhouse
(living space deduction) as well as construction of a sunroom (living space addition)
and combined these two changes yielded a net decrease in living area on the
property, thus making structures on this lot eligible for protection as a pre-1978
structures in accordance with the Bylaw.
6. Peer Review of Materials by Greg Berman (Town’s Peer Reviewer) – It is our
understanding that all materials have been made available to Mr. Berman
throughout the Public Hearing process; this includes the NOI, all Public Hearing
PowerPoint presentations, written response to comment documents, draft Findings
of Fact and Draft Order of Conditions. We will be pleased to provide Mr. Berman,
through Commisison staff, with any additional files that are part of the submission
record for the Expanded Project.
Nantucket Land Council and Applied Coastal Research and Engineering, Inc.
Comments
1. Coastal Bank Erosion Rate is Incorrectly Calculated – The volume of sand
contributed from the Sconset Coastal Bank due to coastal erosion was calculated in
accordance with the long-standing method utilized by MassDEP and CZM. The
sand contribution volume, and the corresponding sand mitigation volume, is
presented in NOI Section 2.3, discussed in the correspondence to the Commisison
Nantucket Conservation Commission 4
January 4, 2019
dated November 2, 2018 and was presented to the Commisison during the
November 5, 2018 Public Hearing. See November 5, 2018 presentation slides 47 –
50.
2. Rate of Shoreline Erosion has Increased since the Geotube System was
Installed (author presented a graph despicting pre-geotube shoreline change to post-
geotube shoreline change). – See response to comment document dated November
2, 2018 specifically in response to Applied Coastal comments 4 and 5 on pages 27
– 30. Also see the presentation made at the November 5, 2018 Public Heaing that
focused on sediment transport and sand mitigation.
The figure below depicts the rate of shoreline change (November 5, 2018
PowerPoint Presentation slide 14) for four time periods. Examination of this figure
shows that in the existing project area, and immediately adjacent shorelines, the rate
of change has varied over time and the post-geotube period is within the scatter of
the pre-geotube time periods.
Nantucket Conservation Commission 5
January 4, 2019
3. The Author Refers to Shoreline Changes at WHG Profile 90 as an Example
of Shoreline Change Along the Entire Project Shoreline -- One datum point, i.e.
Profile 90, is not representative of the nearly 4,000 linear foot project area
(comprised of the existing and Expanded Project areas). The SBPF consultants used
and synthesized all data to calculate the Coastal Bank contribution rate and to
evaluate potential effects to adjacent beaches. The purpose of the monitoring
program conducted by Woods Hole Group, Inc. (“WHG”) is to evaluate potential
effects on nearby Coastal Beaches from the existing project. As stated in the most
recent WHG shoreline survey report (Southeast Nantucket Beach Monitoring 77th
Survey report, September 2018) no evidence of accelerated erosion post-geotube
has been observed exceeding historical observations.
4. The Author Presents a Shoreline Retreat Rate of 14.8 lf/yr at Profile 90 Since
the Geotube Project was Installed – Per the author’s comment that retreat rate
would yield a Coastal Bank contribution rate of 32.8 cy/lf/yr. We cannot find such a
rate in the WHG data, nor can we replicate that annual erosion rate based on our
review of WHG data.
If that rate had occurred over the past 5 years, since the three geotube emergency
project was installed, the beach and/or bank would have retreated approximately 74
feet. That loss is not supported by the monitoring data.
Second, a review of annualized shoreline change for a number of time periods is
presented below for Profile 90. Profile 90 is about 1,050 feet south of the existing
geotube system, and changes at this profile cannot be directly attributed to the
existing geotube project due to the distance. The data in Table 1 was obtained
from the WHG 77th Survey Report, Appendix B.
As evidenced in Table 1 below, various annual erosion rates can be determined for
this location of shoreline (Profile 90) based on the time period chosen, with erosion
rates at Profile 90 ranging from 0.54 ft/yr to 2.9 ft/yr depending on the chosen time
period; likewise periods of accretion can also be identified in the data. That is why
using data from one profile and extrapolating it to the entire shoreline is not
meaningful. Thus, the long-standing method accepted by MassDEP and CZM, i.e.
bank retreat times bank height times project length (as was done for the proposed
extension project) is the accepted practice used by MassDEP and CZM.
Nantucket Conservation Commission 6
January 4, 2019
Table 1. Review of Shoreline Change at Profile 90 for Various Time Periods
Starting Date &
Position (feet)(1)
Ending Date &
Position (feet)
Total Change
(feet)
Annualize Rate
of Change
(feet / year)
Comments
10/2003 / -104.3 9/2018 / -120.0 21.5 ft Retreat 1.05 ft/yr Retreat
15 year period straddles
existing project
installation
11/2001 / -138.6 9/2012 / -130.5 8.1 ft
Accretion
1.62 ft/yr
Accretion
11 year period before
large erosion event
winter of 2012/2013 &
existing project
installation
10/2003 / -104.3 9/2012 / -130.5 26.2 ft Retreat 2.9 ft/yr Retreat
9 year period before
large erosion event
winter of 2012/2013 &
existing project
installation
9/2013 / -117.3 9/2018 / -120.0 2.7 ft Retreat 0.54 ft/yr Retreat
5 year perid after
2012/2013 erosion
event & existing project
installation
10/2015 / -115.9 9/2018 / -120.0 4.1 ft Retreat 1.37 ft/yr retreat
3 year period after 4th
tier added to existing
project
(1) Position is feet from a previously established baseline point.
To evaluate abutting shoreline reaches potentially effected by the presence of the
existing geotube system we examine shoreline changes at the profiles closest to the
existing project. See Table 2 below which examines the shoreline change at
Profiles 92 and 92.1 to the north, and 90.85 and 90.8 to the south of the existing
geotube system, based on data from the WHG 77th Survey Report, Appendix B.
Nantucket Conservation Commission 7
January 4, 2019
Table 2. Review of Shoreling Change Adjacent to the Existing Geotube System
Profile Starting Date &
Position (feet)(1)
Ending Date &
Position (feet)
Total Change
(feet)
Annualize Rate of
Change (feet / year)
92.1 10/2014 / -1.7 9/2018 / +5 6.7 ft Accretion 1.68 ft /yr Accretion
92(2) 10/2014 / -55.7 9/2018 / -61.3 5.6 ft Retreat 1.4 ft /yr Retreat
Existing Geotube Project
90.85 10/2014 / -2.1 9/2018 / +4.9 7.0 ft Accretion 1.75 ft / yr Accretion
90.8 10/2014 / -1.3 9/2018 / +7.3 8.6 ft Accretion 2.15 ft/yr Accretion
(1) Position is feet from a previously established baseline point.
(2) Approximate location of the clay head
Diffusion of sand off the existing geotube system is the likely sediment transport
mechanism leading to the accretion obeserved immediately to the north and south
of the existing system. At Profile 92 there was about a 10-foot retreat documented
from October 2014 to October 2015. Since October 2015 the shoreline has been
relatively stabile at Profile 92, with 4.4 feet of accretion observed from October
2105 to October 2018, and that correlates to an annualized accretion rate of 1.47
feet per year.
The WHG shoreline monitoring and shoreline volume data document changes to
the beach and nearshore – toe of the Coastal Bank to -5 feet MLW. The purpose of
the WHG monitoring program is to observe and document changes to nearby
beaches, while annual bluff surveys conducted by SBPF present accurate
measurements of sediment contributed off the existing sand template and the
adjacent unprotected bluff both north and south of the existing geotube system. The
most recent survey of the Sconset Bluff is presented in the May 2018 Aerial Survey
Report submitted to the Conservation Comisison in September 2018. The bluff
surveys provide accurate year-to-year sediment contributions and average sediment
contribution volumes over time, and represent short-term mitigation volume needs.
As described in the NOI Section 2.3 (discussed in the correspondence to the
Commisison dated November 2, 2018, and was presented to the Commisison
during the November 5, 2018 Public Hearing. See November 5, 2018 presentation
slides 47 – 50) calculaton of the Coastal Bank contribution rate follows the
MassDEP and CZM practices and is based on the retreat rate times the height of the
Coastal Bank times the length of the geotube system. The purpose is to calculate
Nantucket Conservation Commission 8
January 4, 2019
the volume of sediment contributed from the Coastal Bank, a glacial landform
which is not renourished by the littoral drift system, to ensure that volume of
mitigation sediment will continue to be contributed to the littoral drift system after
the geotube system is installed. WHG monitors the shoreline position and volume,
from the toe of the Coastal Bank to -5 feet mean low water (MLW) which includes
the Coastal Beach and the nearshore of Land Under the Ocean. These Coastal
Wetland landforms are renourished by the littoral drift system. Therefore it is
incorrect to use the WHG shoreline change data to determine sand mitigation
volume because the mitigation volume is only associated with the contribution from
the Coastal Bank.
5. A properly designed shoreline stabilization project using best-available
measures should not transfer the burden of losing a home or property from project
location to the neighboring properties - We concur that a properly designed
shoreline stabilization project using best-available measures should not transfer the
burden of losing a home or property from the project location to the neighboring
properties. Further to this point though, a properly designed shoreline stabilization
system will not necessarily prevent the loss of shoreline or loss of a home due to
shoreline erosion beyond the limits of the shoreline stabilization system. Inherently,
the geotextile tubes stabilize the Coastal Bank protected by the geotubes. The
adjacent properties are still subject to natural coastal erosion and will still be in
danger of loss. The entire Coastal Bank system is experiencing erosion and the
sediment placed in front of and above the existing geotextile tubes is intended to
address the lack of sediment being provided from the protected section of bluff.
This does not and cannot offset the natural Coastal Bank erosion losses elsewhere
along the bluff and shoreline to the north and south of the project. Continued
natural Coastal Bank erosion leads to the request to extend the existing geotextile
tube system and protect a longer section of coast that is imminently threatened by
erosion. Mitigation sand will be provided to offset the sand that would have been
contributedto the adjacent Coastal Beaches without the Expanded Project.
6. SPBF Presented a Fixed Volume Sediment Alternative In Lieu of The
Proposed Adaptive Mitigation Plan – No, the fixed volume option was not offered
as an alternative to the adaptive sand mitigation protocol proposed by SBPF. SBPF
stated that should the Commission believe the adaptive sand management proposal
be too combersome to implement, then the alternative would be a fixed mitigation
sand volume program, consistent with standard mitigation programs permitted by
the MassDEP. SBPF contiues to propose the adaptive sand mitigation protocol as
Nantucket Conservation Commission 9
January 4, 2019
the best available measure to minimize potential adverse effects to nearby Coastal
Beaches.
We attached the response to comment document dated November 30, 2018
because that augments the information presented above and presents a summary
comparison of the proposed Expanded Project to the existing project, as well as a
comparison to the existing OOC special conditions and the suggested draft
preliminary OOC special conditions.
Please contact me at (978) 897-7100 or via email at ddunk@epsilonassociates.com
with questions of comments regarding this matter.
Sincerely,
EPSILON ASSOCIATES, INC.
Dwight R. Dunk, LPD, PWS, BCES
Principal
cc: MassDEP-SERO
J. Posner, SBPF
A. Gasbarro, Nantucket Eng. & Survey
S. Cohen, Cohen & Cohen Law, PC
G. Wood, Ruben and Rudman, LLP
G. Thomson, W.F. Baird & Assoc.
L. Smith, Epsilon
R. Hamilton, Woods Hole Group
encl. Correspondence to the Nantucket Conservation Commission dated
November 30, 2018
PRINCIPALS
Theodore A Barten, PE
Margaret B Briggs
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
Maria B. Hartnett
ASSOCIATES
Richard M. Lampeter, INCE
Geoff Starsiak, LEED AP BD+C
Marc Bergeron, PWS, CWS
3 Mill & Main Place, Suite 250
Maynard, MA 01754
www.epsilonassociates.com
978 897 7100
FAX 978 897 0099
21597/2018/Expanded Project/NOI/Public Hearing Comments
November 30, 2018
Nantucket Conservation Commission Via Electronic Mail and U.S. Mail
2 Bathing Beach Road
Nantucket, MA 02554
Subject: Response to Comments from the November 19, 2018 Hearing on the
Expanded Baxter Road and Sconset Bluff Storm Damage Prevention
Project (DEP File No. SE 48-3115)
Dear Commission Members:
On behalf of the Sconset Beach Preservation Fund (“SBPF”), Epsilon Associates, Inc.
(“Epsilon”) submits responses to questions and comments raised Commissioners and
the public during the November 19, 2018 Public Hearing, see Attachment 1. We
also provide a comparison of the Existing Project and the Expanded Project to
highlight the similarities between the two projects, see Attachment 2.
SBPF believes that we have provided all of the information requested by the
Commission and responded to concerns expressed by the Commission and the
public. We look forward to hearing any final comments from the Commission and
the interested public at the December 3, 2018 Public Hearing, and we hope to be
in a position to close the Public Hearing after you have had a chance to review the
information attached hereto.
Please contact me at (978) 897-7100 or via email at ddunk@epsilonassociates.com
with questions of comments regarding this matter.
Sincerely,
EPSILON ASSOCIATES, INC.
Dwight R. Dunk, LPD, PWS, BCES
Principal
Nantucket Conservation Commission 2
November 30, 2018
cc: MassDEP-SERO
J. Posner, SBPF
A. Gasbarro, Nantucket Eng. & Survey
S. Cohen, Cohen & Cohen Law, PC
G. Wood, Ruben and Rudman, LLP
G. Thompson, W.F. Baird & Assoc.
L. Smith, Epsilon
R. Hamilton, Woods Hole Group
encl.: Attachment 1 – Comments and Responses from the November 19, 2018
Nantucket Conservation Commission Public Hearing
Attachment 2 – Comparison of Permit Decisions for the Expanded Baxter
Road and Sconset Bluff Storm Damage Prevention Project
Attachment 1
Comments and Responses from the November 19, 2018
Nantucket Conservation Commission Public Hearing
21597/Light House 1 of 8 Questions & Answers
Epsilon Associates, Inc.
Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project
(DEP File No. SE48-3115)
Comments and Responses from the November 19, 2018
Nantucket Conservation Commission Public Hearing
Eligibility for Protection
Q: What is justification for protecting the southern-most lots? The bluff is vegetated in this
area.
A: Protection of southern lots (from 59-67) can prevent the Bluff Walk which is open and in
place from closure. The Bluff Walk is closed north of 67 Baxter Road. The Bluff Walk is
used by many hundreds of walkers per day through spring, summer and fall and can be
considered to be infrastructure. In addition, the homes adjacent to this segment of the bluff
are all qualifying pre-1978 homes. The toe of the bluff has been eroding in this southern
segment for 5+ years with erosion moving from north to south over time. Erosion at the
toe began on the southern-most lot (59 Baxter Road) during the March 2018 storms. The
vegetated face of the bluff has substantially slid in front 63, 65, and 67 Baxter Road, and is
partially sliding in front of 61 Baxter Road. The shoreline in this area, based on Woods
Hole Group (“WHG”) profiles 89.2 to 901, show significant shoreline loss and erosion for
the five-year period of September 2013 – September 2018.
Q. Regarding gap lots for the whole project (existing and proposed), gap lots appear to account
for 50% of the area. How many gap lots are there? There is concern about the number of
gap lots. Acknowledge need for a continuous structure.
A: The Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project (“Expanded
Project”) area (59 – 85 and 107 – 119 Baxter Road) is comprised of 21 lots on the east side
of Baxter Road. Only two (2) of these lots are considered “gap lots”.
All seven (7) lots from 107 to119 Baxter Road are eligible for protection in order to avoid
the loss of Baxter Road infrastructure and eligible pre-1978 homes. Three (3) lots support
pre-1978 homes which provide an additional rationale for eligibility for protection; and
protection of the other four (4) lots is needed to protect public infrastructure.
Of the remaining 14 lots from 85 to 59 Baxter, there is only one (1) vacant lot, 85 Baxter
Road. This lot is eligible for protection to protect public infrastructure and as a “gap lot” to
install a continuous system. Eleven (11) of the thirteen (13) homes on these lots qualify
under both the State and local by-law criteria for protecting pre-1978 homes. The other two
(2) are eligible under the State criteria but potentially ineligible under the local. These two
homes can be considered to be “gap lots” and eligible for protection to construct a
continuous system.
21597/Light House 2 of 8 Questions & Answers
Epsilon Associates, Inc.
Note, the Existing Project consists of three (3) lots with pre-1978 homes and 5 vacant lots.
None are considered to be “gap lots” because protection in front of the vacant lots is
required to protect the Baxter Road infrastructure.
Q. At the southern-most end, the returns abut the dune and deflection off the geotube system
might affect the dunes beyond the proposed expanded project limit. How does this project
protect against erosion of those dunes?
A: Continued natural retreat of the shoreline and bluff adjacent to the Expanded Project limit
from continued erosion means that a gap can be expected to appear overtime where the
returns end. This gap is not the result of accelerated erosion; it is simply caused by the fact
that erosion will continue to move landward where there is no protection. We suggest that
a system of coir rolls like what was just recently approved for the Existing Project, be built
into the OOC for this Expanded Project and be installed in these gaps as they occur.
Erosion Rate and Sand Mitigation
Q: How are the sand erosion rate and mitigation volumes calculated? Why are they based on
length-weighted averages? What if future rates of erosion on the bluff are different than
they have been historically? How does design and template management account for an
increased rate of erosion? How does design and template management account for
different rates of erosion on different locations along the template?
Q. How does the proposal address future massive erosion rates? The Project needs to be
flexible; it seems that the Project will place a structure in front of a natural contributor and
we won’t know the impacts down-drift?
A: The Expanded Project design and the proposed Template Sand Replenishment Protocol
(“Adaptive Protocol”), are based on the Massachusetts Department of Environmental
Protection (“MassDEP”) Regulations and Massachusetts Office of Coastal Zone Management
(“CZM”) Policy and rely on long-term historic erosion rates, or contribution rates, to
determine the future sediment mitigation volume and rate. The Applicant has followed the
procedures established by MassDEP and CZM to determine sand mitigation volume. That
rate is calculated based on the project specific long-term rate of erosion and the height of
the bank. This results in different erosion and mitigation volumes in different segments of
the bluff. This information was collected for different segments and then using weighted
averaging a volume (i.e. cubic yards/linear foot/year) is derived. The weighted average for
the entire 3,800 feet of the project area is 8.8 cy/lf. The weighted average for the current
950 foot project is 12 cy/lf.
Sand is placed on the face of the geotubes so it can be washed off and contribute to the
littoral drift system. The proposed Adaptive Protocol mitigation measure provides a
substantial volume of sediment to the system to maintain down-drift landforms. Results of
21597/Light House 3 of 8 Questions & Answers
Epsilon Associates, Inc.
monitoring to date for the Existing Project demonstrate down-drift Coastal Beaches are
maintaining their historic size and not harmed by the Project1.
Q. There seems to be a big gap in the Applicant’s proposed mitigation volume and what
Applied Coastal has been saying.
A: Applied Coastal has not used the methodology for calculating an erosion rate or sand
mitigation volume that is consistent with MassDEP Regulations and the CZM Policy, and as
required and used in other similar projects. It is unclear what methodology Applied Coastal
is using in their analysis and they have not provided a specific proposed Coastal Bank
erosion rate or sand contribution volume. The Applicant has followed the MassDEP
Regulations and the CZM Policy in their calculations. Further, the Applicant has calculated
the pre-construction project site-specific Coastal Bank erosion rates based on a 23 year
record (1994 – 2017) for the northern portion of the Expanded Project and a 14 year record
(2003 – 2017) for the southern portion. Both of these time periods include the erosion
event that occurred in 2012-2013.
Q. What are the pros and cons of the Adaptive Sand Mitigation system proposed? Why is the
Applicant proposing this?
A. The Adaptive Protocol template management accounts for different annual sediment loss off
the face of the template and adjusts for “big years” and below average years of sand loss by
re-covering exposed geotubes after erosion events throughout the year. This approach
accounts for varying erosion rates from year-to-year. Because the Adaptive Proposal calls
for “re-filling” the sand template to 22 cy/lf for each storm season, it assures that a
substantial volume of sand is available each year.
The typical method of sand mitigation calls for a specific amount of sand to be delivered
each year regardless of whether it is an above or below average year of sand loss. After a
“big year” there may not be as much sand available in the template using the standard
method as there would be following the Adaptive Protocol.
The Adaptive Protocol is a practical approach to make sure that an adequate volume of
sand is being contributed off the template over time because the required monitoring
provides data every year showing how much sand was contributed from the template the
previous year, and how much sand was contributed from nearby unprotected bluff areas the
previous year. The Adaptive Protocol does not rely solely on the historic rate of erosion of
the bluff as does the standard mitigation approach used by MassDEP and CZM.
Storing excess sand on top of the template for re-covering exposed tubes makes adequate
sand volume is available for use wherever erosion occurs along the face of the template.
21597/Light House 4 of 8 Questions & Answers
Epsilon Associates, Inc.
Q. Isn’t it simpler to require a specific amount of sand mitigation each year regardless of the
rate of erosion and sand contribution?
A. The traditional method is an annual contribution based on the calculation method we have
described above and elsewhere in the NOI and hearings. That amount is 8.8 cy/lf for the
approximately 3,800 lf project. We are prepared to provide this annual amount as an
alternative to the Adaptive Protocol approach if the Commission prefers. Further, we would
be willing to include a template of 22 cy/lf as part of the initial construction. However, in
future years if more than 8.8 cy/lf washes away in a given year, as was the case last year for
example where the existing template contributed 20 cy/lf, then the balance in the template
would decline since only 8.8 cy/lf would be added. In below average years, less than 8.8
cy/lf might wash away in which case the template would increase in size when the set 8.8
cy/lf amount is placed on the template.
Q: Is there is a cut off to the amount of sand nourishment per linear foot?
A: There is no cut-off. The Adaptive Protocol calls for having a stockpile of 22 cy/lf on the
template (in front of the tubes and on top of the tubes) before the start of each storm season.
Sand from atop the template will be used to re-cover exposed tubes after erosion events.
Should more sand be required during the storm season more sand will be imported to the
Project site to ensure exposed tubes can be re-covered.
Q: The twice-a-day high-tide cycle picks up sand on the beach; if there is no sand on the
template, there is nothing to be carried into the system.
A: The toe of the geotube system is approximately 70 to 75 feet landward of the mean high
tide line (el. +3 feet). Therefore, during most days the water and waves do not reach the
template therefore there is no interaction between the normal tide elevations and the
template. There are a number of occasions during the year during intense storms, when
wave run-up extends up to the toe of the geotube system, and sand can be carried off the
face of the template, as designed. In longer storms there are a few occasions when the
geotubes are exposed and no more sand is available to be washed away during that storm
event. Data from the project shows that this occasional shortfall is offset by other occasions
when sand is contributed more quickly and more readily than it is from the erosion of
unprotected bluff. Further, as described by the Applicant’s coastal scientists and engineers,
the timing of the contribution of sand from the geotubes does not have a material impact on
the availability of downdrift material. Further, the data from regular beach surveys has
shown no evidence of impact of the project on downdrift beaches.
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Q. Some commissioners continue to be concerned that the timing of nourishment, and the
time periods when the geotubes are exposed may negatively impact neighboring beaches
by depriving them of adequate sand.
A. The Applicant’s coastal scientists and engineers demonstrated how the littoral drift system is
affected by many factors and the precise timing of sand contribution is not a material factor.
Annual volume is the determining factor. Further, the post-erosion event re-covering of the
geotubes provides numerous additional volumes of sand available for subsequent storms
during the year. More precise timing is not a practical option. In addition, the appropriate
standard is “best available measures” which either the typical annual deliver or Adaptive
Protocol meet.
Q. The Commission will never know how much would have been contributed from the bluff if
the geotube protection were not in place.
A. While it is not possible to know what erosion rate may be for this segment of the bluff in the
future if it were not being protected, we do have 25 years of detailed data and decades of
additional data showing the rate of erosion over the past 100 years. The MassDEP
Regulations and CZM Policy rely on long-term historic erosion rates, or contribution rates,
to determine the future sediment mitigation volume and rate. The Applicant has followed
the procedures established by the MassDEP and CZM to determine sand mitigation volume.
Q. Is the calculation of the erosion rate for the southern portion of the project based on too
long a term? Would a shorter-term rate be more appropriate?
A: Consistent with the MassDEP Regulations and the CZM Policy, the Applicant has calculated
pre-construction project site specific Coastal Bank erosion rates based on a 23 year record
for the northern portion of the Expanded Project and a 14 year record for the southern
portion. Both of these time periods include the significant erosion event that occurred in
2012-2013.2 Using a short-term rate is considered less accurate since it can be skewed by
short term events. As an example, if one were to select either a particularly big year or
small year and then extrapolate from the data for that short term period only one would get
a highly inaccurate result – either too high or too low depending on whether a high or low
year is selected.
Additionally, review of the Existing Project by Milone and MacBroom, Inc. (letter dated
November 12, 2013 and referenced in the OOC SE48-2824) confirmed the use site specific
data to determine bank erosion and mitigation sand volume. The author also indicated that
an adaptive mitigation program may be warranted because future conditions may warrant
lower sand mitigation volumes or a higher sand mitigation volumes in any given year.
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Q: With this design a large portion of sand on the template is not available because it is on top
of the template.
A: The sand atop the template is essentially a sand stockpile, for use to re-cover exposed
geotubes quickly after storm events. Thus, it is available throughout the storm season (and
year) to periodically replace sand in front of the geotubes so that sand remains available to
the littoral drift system throughout the year.
Impact of Project on Interest of Coastal Beach and Habitat
Q: The NOI identifies up to 67,000 SF of beach alteration. How are the functions of beach
being maintained? How can it respond?
A: As depicted on the Expanded Project drawings, the lower two (2) rows of geotubes are
buried beneath the beach surface, and the geotubes are located about 70 feet to 75 feet
landward from the mean high-water line, therefore a significant amount of beach remains
available to respond to tidal and wave action.
The MassDEP Regulations acknowledge that coastal engineering structures are likely to be
constructed on Coastal Beach and allow for that in 310 CMR 10.27(3).3 The Existing
Project is placed on the back of the beach, as is the proposed Expanded Project. There is
no other place to construct it without excavating into the bluff itself. The Expanded Project
was designed to minimize adverse effects on nearby coastal beaches and the proposed
Adaptive Protocol sand management program is a “best available measure” to minimize
adverse effects on nearby coastal beaches, in compliance with the MassDEP Regulations.
The municipal Bylaw regulations are no more stringent related to the stated concern.
Q: Will plastic fibers from the geotubes enter the environment? What impact might those
have?
A: This topic is beyond the scope of the Wetlands Protection Act and the Nantucket Wetlands
Protection Bylaw. Further, the study of microplastics in ocean environments is still in its
infancy.
In further response to this question, we contacted manufacturers of geotextile tubes, and the
product anticipated for this application is a high tensile strength woven polypropylene.
Geotextiles made of polypropylene have a life expectancy of more than 200 years.4 In
addition to the existing Project, a longer-term application of similar geotubes in NJ has had
no fabric failures since it was installed more than 20 years ago5.
Q: What is the Bank Swallow breeding season? Arrival and departure dates?
A: The dates provided by Dr. Kennedy (letter dated July 3, 2017 previously submitted to the
Commission) are based on his more than 95 surveys along the east coast of Nantucket.
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Bank Swallows were observed mid-May to mid-August during 44 of those surveys. He
concluded that conducting work between mid-August through March would avoid any
interference with Bank Swallows on the Sconset coast.
Q: Does the project effect seal habitat? Seals are protected by the Marie Mammal Protection
Act (“MMPA”).
A: No, the geotube system will not interfere with “seal habitat” because it is located well
above mean high water and the all work will occur above mean high water. Also, sufficient
beach width will remain to accommodate seals that may pull up on shore. Further, the
MMPA is not within the jurisdiction of the Commission and the Project site is not estimated
habitat for any seal species protected by the Massachusetts Endangered Species Act.
OTHER ISSUES
Q: How will existing stairs down the bluff be handled?
A: Existing stairs will be retained. People using the stairs will need to walk along the top of the
template to the ramps and the ends to reach the beach.
Q: Has the Commission granted a waiver for a CES in front of substantially improved, post-
1978 house or empty lot?
A: Yes, for the Existing Project (DEP File No. SE48-2824). The waiver was granted to protect
pre-1978 houses and public infrastructure. Empty lots are located between the top of the
bluff and the roadway, thus by definition some empty lots (gap lots) are protected as a
means to protect the public infrastructure.
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End Notes
1 See Tables 2 and 3 in the Southeast Nantucket Beach Monitoring - September 2018 - 77th Survey Report,
dated October 2018.
2 Standard practice is to use the CZM shoreline change maps to determined long-term erosion
rates. Along the Sconset shoreline that long-term data (approximately 165 years) yields less than
a 1 foot per year of shoreline loss. That erosion rate was rejected, and the project specific
erosion during the periods 1994 – 2017 were used as the more representative erosion rates for
calculating sand mitigation volume.
3 310 CMR 10.27(3) reads as follows (underline added for emphasis):
“… 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.”
Recall the proposed expansion project is submitted and reviewable pursuant to 310 CMR
10.30(3)(a) for Coastal Banks which reads as follows:
“(3) No new bulkhead, revetment, 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 10.21 through 10.37 or constructed pursuant to a Notice 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 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, and …”
4 Ivy, N, & B. Garner. 2016. Quality control and quality assurance for geotextiles in Geotextiles:
from Design to Applications, pp 565-575. Woodhead Publishing, Elsevier Ltd.
5 Email correspondence with Mr. Peter Kaye, PK Environmental, LLC (November 26, 2018)
Attachment 2
Comparison of Permit Decisions for the Expanded Baxter Road and
Sconset Bluff Storm Damage Prevention Project
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Comparison of Permit Decisions for the Expanded Baxter Road and Sconset Bluff Storm Damage
Prevention Project (DEP File No. SE48-3115) to the Previously Approved Baxter Road and Sconset
Bluff Storm Damage Prevention Project (DEP File SE48-2824)
The pending Notice of Intent (DEP File No. SE48-3115) seeks an Order of Conditions (“OOC”) from
the Nantucket Conservation Commission (“Commission”) that is substantially similar to the
decisions that were already made by the Commission when it issued the OOC for the Existing
Project (DEP File No. SE48-2824). This document is provided to assist the Commission evaluate
the information provided during the Public Hearing process to identify the substantive decisions
that need to be made for the Expanded Baxter Road and Sconset Bluff Storm Damage Prevention
Project (“Expanded Project”), as compared to determinations that were made previously for the
Existing Project. These determinations are substantially the same for both the Wetlands Protection
Act (“WPA”) and the Nantucket Wetlands Protection Bylaw (“Bylaw”).
Table 1 on the following page compares the Expanded and Existing Project relative to project
purpose, design, mitigation and monitoring. As shown, there is little difference between the
Existing Project and the extension of this geotube system to the north and south, i.e. the Expanded
Project.
Table 2 on page 3 compares permitting decisions by the Commission, again comparing the
decisions made for the Existing Project to those needed to authorize the Expended Project. This
comparison is based on the OOC for SE48-2824 and the draft findings of Findings of Fact / Special
Conditions submitted to the Commission on November 16, 2018.
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Table 1. A Summary Comparison of the Existing and Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project
PROJECT ELEMENT EXISTING PROJECT EXPANDED PROJECT
Project Purpose : +/- 950 feet to protect 2 homes and
public infrastructure (fronting 5 vacant
lots to protect public infrastructure; gap
lots from a pre-1978 house perspective).
+/- 2,900 feet to protect 21 lots - 16
homes and 5 vacant lots (to protect
public infrastructure) or “gap lots” per
the state definition1.
Geotube System Design:
Geotube Layout Four tier geotube configuration covered
by sand template.
Same design. Difference is lowest
geotube set at elevation -3 feet MLW
instead of 0 feet MLW
Geotube Returns Sloped returns that tie into adjacent
Coastal Bank at a shallow angle.
Same design.
Return Extensions Coir rolls approved November 28, 2018. Add Special Condition to install coir roll
return extensions when appropriate.
Sand Template
Management:
Place sand on template at a rate of 22
cy/lf/yr and use that sand stockpile to
recover exposed tubes after erosion
events. Import sand during storm season
as needed to replenish stockpile.
Fill template to 22 cy/lf before each
storm season and use that sand stockpile
to recover exposed tubes after erosion
events. Import sand during storm season
as needed to replenish stockpile.
Monitoring: Extensive monitoring program:
Shoreline change quarterly;
Bathymetric Survey semi-annually;
underwater video semi-annually;
post-storm inspections;
template survey annually.
Extensive program with minor
modifications2:
Shoreline change semi-annually;
Bathymetric Survey annually;
Underwater video once every 3 year;
Post storm inspections
Template survey annually
Reporting: Annual Report and interim reports to the
Commission
Same
Notes:
1. Per the Nantucket Bylaw 14 homes are eligible as pre-1978 structures, 2 are non-eligible structures but
can be protected as “gap lots”, and 5 are vacant lots eligible for protection to protect public infrastructure
from damage.
2. Correspondence from Greg Berman, Woods Hole Sea Grant | Cape Cod Cooperative Extension to Jeff
Carlson (Natural Resources Coordinator, Town of Nantucket) dated April 7, 2017 Regarding the
Independent Review of the 2016 Annual Report, noted the following:
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. (pg. 4)
Wetland Well Monitoring – If the data from 2001-2007 shows similar dry levels as this project the well
monitoring could be discontinued. (pg. 5)
Beach Invertebrate Monitoring – The invertebrate monitoring could be discontinued as no impacts to
the few species have been observed. (pg. 5)
Underwater Video Monitoring – Video monitoring likely is not needed yearly. (pg. 6)
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Table 2. A Summary Comparison of the Permitting Decisions for the Existing and Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project
EXISTING PROJECT EXPANDED PROJECT
Findings of Fact:
Contains 18 Findings of Fact. All Findings are the same, except those that do not apply:
No. 15 that referred to the Emergency Project;
No. 16 that referred to maintaining the 3 tier system;
Nos. 17 c. – e. that referred to the Emergency Project and SOC;
Nos. 17 f which is modified (16.c) to remove reference to the
Emergency Project.
Special Conditions:
OOC included 40 Special
Conditions, Nos. 19 - 59
32 preliminary Special Conditions were submitted for review,
Nos. 1 – 32.
Conditions 20., 21., 22., 24., 25.,
29., 30., 31., 34., 35., 36., 37., 39.,
40., 42., 43., 48., 49., 52., 54., 55.,
57., 58., and 59.
Remain essentially the same, minor changes to reflect the
Expanded Project and renumbered in preliminary OOC
submitted for consideration by the Commission on November
16, 2018.
The following 10 of 40 conditions are modified as summarized below:
No. 19 - Project Description. No 1. - Modified to describe Expanded Project Description.
No. 26 - Relative to 4th tier of
geotube.
No. 7 – Modified to address restoration of beach with sand
excavated to install geotubes.
No. 27 - Relative to beach
monitoring.
No. 8 – Modified to reflect proposed changes to monitoring
frequencies.
No. 28 - Bathymetric profiles. No. 9 – Modified annual profile. .
No 32 - Sand mitigation volume. No 13 – Modified to condition the adaptive sand template
management protocol.
No. 33 - Storage of sand on beach. Deleted. Not proposed. Sand ramps provide excess sand
storage.
No. 41 - Addresses term of approval,
states date until which expansion
NOI can be filed and conditions
applications for modifications.
No. 20 – Modified to deleted reference to January 2018 for any
requests for an expanded project and modifies allowed
modifications to include changed site conditions in addition to
emergencies.
No. 45 - Refers to partial Certificate
of Compliance (“COC”).
No. 23 – Modified to address COC for SE48-2824 in relation to
COC for SE48-3115.
No. 48 – Refers to quarterly surveys
regarding retreat.
No. 24 – Modified to remove reference to quarterly surveys.
No. 53 - Success Criteria. No. 27 – Modified only to refer to adaptive sand mitigation
(27.a.)
The following conditions are deleted because they are not applicable to the Expanded Project:
Nos. 23., 38., 46., 47., 50., & 51.
The following conditions are deleted because they have been met / completed:
Nos. 44. & 56.