HomeMy WebLinkAbout2013_8_6 SBPF Responses_20140523085337567921597/Sconset Storm Damage Prevention 1 Response to 7/30/13 NLC & Applied Coastal Ltr
BAXTER ROAD AND SCONSET BLUFF STORM DAMAGE PREVENTION PROJECT
NOTICE OF INTENT
RESPONSES TO COMMENT LETTERS FROM NANTUCKET LAND COUNCIL AND APPLIED
COASTAL RESEARCH AND ENGINEERING DATES JULY 30, 2013
August 6, 2013
The following presents SBPF’s responses to comments and questions presented by the Nantucket
Land Council (NLC) and their consultant, Applied Coastal Research and Engineering, Inc. (Applied
Coastal), in their memorandum dated July 30, 2013. The comments and questions in the letter are
presented in underlined text, followed by responses presented in indented text.
NLC Letter dated July 30, 2013
The application is not complete and it is not possible to fully evaluate the proposed project because
a stamped engineer's plan of existing conditions has not been; provided….
Stamped plans based on an updated LIDAR survey will be provided the week of August 12.
[T]he project as proposed has not met the standards of the state Wetlands Protection Act…
This claim is completely unsubstantiated; the Project’s compliance with the state
performance standards is described in detail in Section 4.0 of the Notice of Intent.
There are a number of performance standards under the local Bylaw and Nantucket Wetland
Protection Regulations that have not been met and will require the justification of a waiver.
Section 2.02 B(2) for coastal beaches: "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".
A waiver will be requested for that portion of the project that will include the toe of
the revetment that is to be buried below the beach. Contrary to Ms. MacKinnon’s
assertion, the terraces are not an effective long-term solution, for those reasons
documented in the Alternatives Analysis provided as Attachment E to the NOI.
21597/SBPF 2 Response to July 30 Nantucket Land Council
Section 2.05 B(l) for coastal banks: “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".
The Board of Selectmen has reviewed multiple alternatives for relocating the threatened
public infrastructure, and a comprehensive plan is being developed for this eventuality.
The Project’s compliance with this regulation is presented in Section 5.0 of the NOI.
The Board of Selectmen are not planning for alternative access at the moment. The
Town conducted a preliminary evaluation of providing additional access to Baxter
Road. This would involve the need for takings, large damage awards and
substantial costs to relocate the road and utilities, if this is even feasible. Given the
substantial disadvantages associated with alternative access, the Town is not
pursuing this option at the moment. Rather, the Town has entered into a MOU
allowing the SBPF to try to protect the road via the revetment project.
The Nantucket Wetland Protection Regulations also state under Section 2.02 B(6) for coastal
beaches and Section 2.05 B(5) for coastal banks: "All work on projects which are not water
dependent shall maintain at least a 25-foot natural undisturbed area adjacent to a coastal
beach/bank. All structures which are not water dependent shall be at least 50 feet from a
coastal beach/bank".
The proposed project is not water dependent under the local definition and will require
waivers from the above performance standards.
The local definition of Water Dependent Project or Uses is “projects which require
direct wetlands access for their intended use and therefore cannot be located out of
the Area Subject to Protection Under the Bylaw…” The revetment must be located
on the coastal bank and coastal beach wetland resources for the intended use of
providing storm damage prevention, thus it clearly meets the definition of a water
dependent project. The Nantucket Conservation Commission on 11/14/12 issued an
Order of Conditions approving a coastal engineering structure at 93 and 99 Eel Point
Road (SE48-2479) and they made the Additional Finding 4 as follows: “The
Commission finds that the project is a water dependent project as it requires direct
wetlands access for its intended use and therefore cannot be located out of the Area
Subject to Protection Under this Bylaw.”
21597/SBPF 3 Response to July 30 Nantucket Land Council
Section 2.01 B(8) states: "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".
The loss of 0.8 miles of coastal beach resource area will absolutely result in adverse effects
on wildlife, erosion control, storm damage prevention, and recreation.
The Project’s compliance with this provision is set forth in Section 5.0 of the NOI.
The amount and adequacy of the mitigation volume is discussed in the response to
the Applied Coastal memo below.
Ms. MacKinnon’s general statement about adverse effects on wildlife, erosion control,
storm damage prevention, and recreation ignores the considerable information
already presented to the Commission about the lack of significant impacts (see
Sections 4.0 and 5.0 in the NOI; “Responses to Questions from the Nantucket
Conservation Commission asked at Public Hearing on July 24, 2013”; technical
memo from Mike Ludwig dated January 23, 2012 and submitted to the
Conservation Commission on July 24, 2013; and Public Access Plan included in
July 31, 2013 hearing presentation).
These documents demonstrate the following:
There will be no adverse impacts to wildlife, including mole crabs and sand
fleas.
Public access will be maintained or enhanced, through the provision of a
walkway along the top of the revetment and additional stairs. The existing
Sconset Foot-path will be protected.
The project will benefit erosion control and storm damage prevention by
protecting the bank while also providing annual sand mitigation.
Section 2.05 B(3) for coastal banks under the local regulations states: "All projects shall be
restricted to activity as 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 ".
We do not agree that the proposed nourishment schedule and volumes are sufficient to
ensure no adverse impact on the use of the bank as a sediment source.
The amount and adequacy of the mitigation volume is discussed in the response to
the Applied Coastal letter below.
The applicant has also stated that their project as proposed will result in the complete loss of a
significant area of coastal beach resource area protected by your regulations.
21597/SBPF 4 Response to July 30 Nantucket Land Council
We have stated that the project may result in some thinning of the coastal beach; however,
sand mitigation will prevent the loss of most of the coastal beach resource area.
Applied Coastal Memo dated July 29, 2013
Although the impacts of this project would cause a complete loss of the sediment supply along the
armored section, the proposed beach nourishment volume computed to mitigate for this loss is not
based on the best available information (e.g. the severe documented bluff erosion over the 2012-2013
season was not included in the mitigation calculations although it was readily available).
See response to #2 below.
In addition, the mitigation approach is not consistent with previous methods presented by SBPF, leading to
concerns that the beach will narrow or disappear for the area fronted by the coastal armoring. The SBPF
representatives at the July 24, 2013 Conservation Commission meeting indicated that they expected
narrowing of the Town-owned beach as a result of this project. No technical information was presented
regarding what techniques would be utilized to maintain the beach fronting the coastal bank or if the
applicant is actually attempting to maintain the beach in the future. The example touted by the applicants'
representative as a comparable project was the revetment along Triton Way in Mashpee. As shown in
Figures 1 and 2, a high tide beach no longer exists along this section of the Mashpee shoreline.
We previously indicated that the coastal beach in front of the revetment would become
thinner; however, sand mitigation will prevent the loss of the beach during all tides.
Applied Coastal is correct that at Triton Way in Mashpee high tide reaches the toe of the
revetment; however, Applied Coastal did not mention that full sand mitigation at the rate of
coastal bank retreat has not been provided in front of this revetment.
1. The Applicant provided numerous examples of armor stone revetments along the coast of
Massachusetts; however it is unclear (a) whether any of these (or other) revetments are in an area with
bluff erosion rates in excess of 5 feet per year and (b) what the long-term impact on downdrift
beaches has been as a result of revetment construction…. Again, the applicant should provide
examples of where revetments have been successful on coastal banks/bluffs with erosion rates similar
to the Sconset Bluff, where the structure has provided long-term bank stability and downdrift impacts
have been negligible and/or mitigated with nourishment.
There are no examples where the conditions are exactly the same as those at Sconset, as
each coastal area has its unique characteristics. However, we did provide many examples
of revetments along shorelines with exposure to Northeasters, which are typically the
storms that produce the most coastal erosion along the Massachusetts coast as they can last
more than one day and over several high tidal cycles. These examples also included many
long revetments that armor almost the entire coastal bank along sections of the coast and
there are no significant downdrift impacts that have been documented. When reviewed as
21597/SBPF 5 Response to July 30 Nantucket Land Council
a whole, these examples show that revetments with sand mitigation can protect an exposed,
eroding coastal bank without adverse effects on downdrift beaches.
2. The applicant provided updated information that indicated between 2003 and 2012, the crest of the
coastal bank from Lot #73 to #119 eroded an average of 3.18 feet per year.… Applied Coastal has
stressed that long-term shoreline change rates provide the best proxy for bluff erosion, as the two
features are linked: once the beach erodes, the base of the bluff becomes exposed to wave energy
and eventually re-adjusts to the beach position. According to the 2010 OCC Alternatives Analysis
(Table 7), the long-term 1994-2009 shoreline change rate is more than 8 feet of erosion per year,
where over the same time- period, Epsilon Associates computed a bluff erosion rate of only 3 feet
per year.
Applied Coastal’s comparison is not valid for the following reasons.
Using the bank erosion rate (not shoreline erosion rate) is the “Best Available
Measure.” This is the standard that has been consistently required by DEP, CZM,
and many local Conservation Commissions.
Applied Coastal compares the 1994-2009 shoreline change rate to Epsilon’s
calculation of the 2003-2012 coastal bank retreat rate and incorrectly asserts that
these erosion rates are “over the same time-period.”
Applied Coastal does not specify what profiles were used in their analysis, so it is
not certain if the same project area is even being considered.
Applied Coastal’s analysis ends at the year 2009 and does not include several years’
worth of more recent data.
[T]he long-term bluff erosion rate from 2003 to 2013 is 5.36 feet per year, based on the data
provided in the NOI and supplemental documents. The applicant should be utilizing the
best available information to provide realistic bluff erosion rates, rather than skewing results
by not including episodic bluff erosion events.
Applied Coastal fails to acknowledge that the data from 2013 were based on spot
measurements (one per lot) of the minimum distance between Baxter Road and the top of
the coastal bank, as noted in our submission, rather than a continuous top of bank line.
The use of spot measurements is not directly comparable to the 2003-2012 top of bank
retreat analysis, which utilizes a continuous top of bank line. The inclusion of 2013
minimum spot measurements skews the bank erosion calculation, which is why we chose
to use the best available information, which is a 2012 orthophoto with a continuous top
of bank line. When the 2013 LIDAR data are available in early August, the long-term
bank contribution erosion rate and volume will be recalculated.
21597/SBPF 6 Response to July 30 Nantucket Land Council
3. Unlike the previous armoring proposal, the applicant no longer is planning to provide nearshore and
beach volume mitigation. The previous proposal included 6.8 cubic yards per linear ft per year as the
nearshore and beach component of the mitigation that would help maintain the stability of the Town-
owned beach fronting the structure. No reason has been provided as to why SBPF has removed this
mitigation volume from their mitigation plan. Overall, the existing proposal represents less than 50% of
the mitigation rate that was proposed in 2012 for a similar project by the same coastal geologist and
engineer.
We have clearly stated that best available measure is the practice of using the bank erosion
rate prior to the installation of a revetment structure. This practice has been used by DEP,
CZM, and many Conservation Commissions. Our previous use of a larger sand volume was
associated with a Pilot project that was not approved.
4. As discussed during the July 24, 2013 meeting, the 2010 site plans are out of date…At a minimum,
updated plans by a licensed professional should be provided to document the existing conditions, as
well as proposed conditions (including any proposed bank re-grading, fill, or excavation).
Stamped plans based on an updated LIDAR survey will be provided the week of August 12.
5. The Shoreline Monitoring Plan should include additional transects on regular intervals (50-100 foot
intervals) immediately updrift and downdrift of the proposed project to monitor the project for end
effects and increased erosion along the adjacent shoreline and coastal bank. The monitoring survey
should be conducted pre- and post- nourishments to allow for quantification of shoreline variations and
movements after the revetment is constructed. This near-field monitoring is critical to ensure that the
structures are not having adverse impacts on adjacent properties due to 'end effects'. Mitigation
volumes associated with addressing 'end effects' are not part of the calculation in #2 above, as these are
associated with wave reflection which would not naturally occur.
We have already stated that we would conduct additional monitoring both updrift and
downdrift of the revetment and provide sand mitigation if end effects are documented.