HomeMy WebLinkAbout60 SE48_3115 SBPF Resp to Public Comment 04_22_19
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
May 16, 2019
Nantucket Conservation Commission Via Electronic Mail and U.S. Mail
2 Bathing Beach Road
Nantucket, MA 02554
Subject: Response to the April 22, 2019 Public Hearing Comments 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 Siasconset Beach Preservation Fund (“SBPF”), Epsilon Associates,
Inc. (“Epsilon”) submits this response to comments made during the Nantucket
Conservation Commission (“Commission”) April 22, 2019 Public Hearing for the
Expanded Baxter Road and Sconset Bluff Storm Damage Prevention Project
(“Expanded Project”).
NANTUCKET COASTAL CONSERVANCY COMMENTS
Five Clarification Points
1. The current 900-foot Geotube Project was intended to be “temporary.”
The SBPF has always sought a long-term Coastal Bank stabilization project to
protect homes and public infrastructure adjacent to the top of Coastal Bank, and the
current geotube project was a “first phase” towards this goal.
This has been addressed repeatedly throughout this Public Hearing process, see
correspondence dated November 2, 2018 and March 1, 2019. The project plans for
the Existing Geotube Project (SE48-2824) are titled “Baxter Road Stabilization
Project.”
This assertion is regularly being taken out of context. The original revetment project
(DEP File No. SE48-2581 – submitted July 2013) sought an Order of Conditions
(“OOC”) for a 4,253 foot long revetment to stabilize Sconset Bluff and protect
Baxter Road from storm damage. The project plans for that design were titled
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“Sconset Bluff Erosion Control Project – Notice of Intent.” Subsequently, an
approximately 1,500 foot long geotube stabilization was sought (DEP File No. SE48-
2610) to stabilize the most imperiled portion of Sconset Bluff and Baxter Road.
While both SE48-2581 and SE46-2610 were pending, the SBPF and Town of
Nantucket (“Town”) jointly sought an Emergency Order to construct an
approximately 1,2490 foot geotube stabilization project to protect structures, public
infrastructure and the Coastal Bank against the imminent danger posed by excessive
erosion, and before the next winter storm season arrived. Although the term
“temporary” was used on the project plans submitted with the NOI (SE48-2610) and
the Emergency Order request in 2013, the intent was always construction of a long-
term Coastal Bank protection project, as was sought in the original NOI (SE 48-
2581), and this request for the Expanded Project. The project plans approved for
the existing geotube system (SE48-2824) are titled “Baxter Road Stabilization
Project.”
The stated purpose for the 3 to 6 year time period as referenced in the Superseding
Order of Conditions (“SOC”) for SE48-2610 and the OOC SE48-2824 was to allow
SBPF time to identify, design and permit a long-term protection project. The
significant monitoring of the Existing Project and prohibition to requesting a long-
term or longer length expansion until January 2018 was to have at least 3 years of
data on the possible effects of the initial geotube system, consistent with a
“demonstration” project.
2. Alternate access to northern Baxter Road not predicated on permitting of
expansion.
The Memorandum of Understanding (“MOU”) and the Alternative Access
Agreement (“AAA”) identify the alternative access as a failsafe measure in the event
the geotube project fails for engineering or performance reasons and that as a result
Baxter Road must be closed.
This also has been addressed previously, see correspondence dated March 1, 2019.
The MOU and the AAA make clear that the alternative access is to be available to
the Town only in the case that the geotube project fails for engineering or
performance reasons and that as a result Baxter Road must be closed. SBPF has
discharged its responsibility as stated in the MOU and AAA in conjunction with
neighborhood property owners and has provided the necessary land area and
engineering plans to the Town on the agreed-upon “back-up” plan. A decision on
the part of the Town to withdraw from the MOU or AAA on a discretionary basis,
even though the project is in compliance with its permit, would eliminate the
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Town’s ability to utilize the property being voluntarily provided at no cost to the
Town under the AAA.
The only mention of removing the geotubes relative to the relocation of Baxter Road
is OOC Special Condition No. 46, which is only triggered after the possible future
relocation of Baxter Road.
3. The Number of days geotubes uncovered remains unknown.
In accordance with the OOC, SBPF notifies the Commission when the geotubes are
exposed by storms, i.e. wave action, and submits work reports that document the
maintenance work (time, type of work and extent of work) to recover and maintain
the geotube system.
4. Number of days walkable beach maintained remains unknown.
The beach remains walkable during non-storm events and the beach (monitored as
the mean low water contour) in front of the geotubes has not migrated landward
since the geotubes were installed.
This topic was likewise previously addressed, see correspondence dated November
2, 2018.
Review of the currently proposed project plans shows there is approximately 80 feet
between the toe of existing geotube template and the mean high water (“MHW”)
contour. Wave run-up during storms may prevent walking on the beach during
storms. The deposition of wrack, and its most landward limit, only demarcates the
most land limit of wave run up during the most recent storm or high wave event.
Wrack will remain in place until the next large storm or wave event occurs and
carries it away, but is not the MHW.
SBPF does not engage a full time monitor to watch the geotubes 24/7. However,
SBPF monitors the beach on a regular basis in accordance with the OOC. There
are a few tide cycles during some storms when the beach in front of the geotubes is,
of course, not walkable. After the storm subsides however, the beach is walkable
again.
The shoreline surveys show that the beach in front of the geotubes is in
approximately the same location as it was when the geotubes were installed (see
Table 3 below). In addition, SBPF inspects the geotubes on a weekly basis and have
yet to find a time when the beach is not walkable.
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5. Rate of erosion has increased, despite public statements by the Applicant
Monitoring data shows that erosion in front of the existing geotubes, and the
immediately adjacent shoreline, has not increased since the geotubes were
installed.
This topic of erosion rates and calculation of erosion rates has been discussed
throughout this Public Hearing process, see correspondence dated November 2,
2018, November 30, 2018, January 4, 2019 and March 1, 2019; and Public
Hearing Presentation dated November 5, 2018.
A long-term record of shoreline monitoring data has been regularly submitted to the
Commission and review of that data has not shown an increase in erosion rates.
That has been explained and documented in the correspondence referenced above,
especially the correspondence dated January 4, 2019. Shoreline monitoring has not
identified any evidence of post-geotube accelerated shoreline erosion rate beyond
historical variation. See excerpts from the January 4, 2019 correspondence below.
Page 4:
“The figure below depicts the rate of shoreline change (Source: November 5, 2018
PowerPoint Presentation, Slide No. 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.”
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Page 5 & 6:
“Secondly, 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.”
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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 strattles
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.
Pages 6 & 7:
“To evaluate abutting shoreline reaches likely effected by the presence of the
existing geotube system we examined 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.”
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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.”
Four (4) alleged examples of adverse impacts caused by expanding the geotube
project
1. The public beach will narrow and eventually disappear. The science is
irrefutable.
The shoreline monitoring data show that the beach in front of the existing geotube
array has not narrowed since it was installed.
Table 3 below, augments the data used to produce Table 2 prepared for the January
4, 2019 correspondence (reproduced above) and includes data from the most recent
profile data (78th Survey Report) for the profiles immediately adjacent to the existing
geotube array plus the profiles within in the existing geotube project area (shaded in
grey). Profiles are presented north to south, with Profile 92.1 at northerly end and
Profile 90.8 at the southerly end.
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Table 3. Review of Shoreling Change Fronting and 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 12/2018 / +5.9 7.6 ft Accretion 1.79 ft /yr Accretion
92(2) 10/2014 / -55.7 12/2018 / -58.8 3.1 ft Retreat 0.73 ft /yr Retreat
91.9 10/2014 / +5.7 12/2018 / +5.9 0.2 ft Accretion 0.05 ft/yr Accretion
91.5 10/2014 / -66.9 12/2018 / -72.7 5.8 ft Retreat 1.36 ft/yr Retreat
91.35 10/2014 / 0.0 12/2018 / +6.5 6.5 ft Accretion 1.53 ft/yr Accretion
91.2 10/2014 / -1.0 12/2018 / +7.0 8 ft Accretion 1.88 ft/yr Accretion
91 10/2014 / -97.9 12/2018 / -102.6 4.7 ft Accretion 1.11 ft/yr Accretion
90.95 10/2014 / -0.2 12/2018 / +3.6 3.8 ft Accretion 0.89 ft/yr Accretion
90.85 10/2014 / -2.1 12/2018 / +5.7 7.8 ft Accretion 1.84 ft / yr Accretion
90.8 10/2014 / -1.3 12/2018 / +3.1 4.4 ft Accretion 1.04 ft/yr Accretion
The above data show the beach in front of the existing geotube project and
immediately adjacent to the geotube array is quite stabile, with 8 of the 10 profiles
showing accretion and only two profiles showing retreat.
Commenters have been predicting the beach narrowing as the inevitable impact of
this Coastal Bank stabilization project as if it were a seawall with no sand
mitigation. However, given the volume of sand conveyed in the littoral system, and
the large volume of sand being contributed off the sand template during storms, the
beach in front of the geotubes has been maintained. These data support the
proposition that the beach in front of the Expanded Project will likewise be
maintained. If it is not, a failure criteria would be triggered in the proposed OOC
requiring action.
2. Immediately upon construction three (3) additional acres of beach habitat will be
destroyed.
To stabilize the Coastal Bank the geotube system needs to be installed on the
Coastal Beach. This is allowed by the State Regulations.
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This has been addressed in the review of the Wetlands Protection Act Performance
Standards see Public Hearing Presentation from October 1, 2018.
The Coastal Beach performance standards allow for the construction of coastal
engineering structures on a Coastal Beach provided they are constructed to protect
pre-1978 buildings. The applicable regulation reads in part:
Any project on a coastal beach, except any project permitted under 310
CMR 10.30(3)(a) [emphasis added], 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. [310 CMR
10.27(3)].
Because the Expanded Project is approval pursuant to 310 CMR10.30(3)(a) this
standard does not prevent the construction of the geotubes on the Coastal Beach.
3. As demonstrated, end scour will continue, resulting in need to extend the
installation
End scour is a localized phenomenon extending only tens of feet from the geotube
array. It is managed by backfilling lost sand after erosion events to maintain the
integrity of the geotube system.
This topic also has been addressed previously, see correspondence dated March 1,
2019 and March 22, 2019.
As stated by Mr. Berman, the Commission’s peer reviewer, end scour during storms
may extend “tens of feet” from the ends of the geotube system. End scour can be,
and is, managed by backfilling exposed returns after erosion events as needed. As
we have noted throughout the Public Hearing process erosion of the adjacent
unprotected Coastal Bank is expected to continue and that will require extensions to
the returns to maintain the connection of the geotube system with the face of the
Coastal Bank. Extensions similar in design to those approved by the Commission as
an Amended OOC (dated November 28, 2018) are expected to be needed in the
future.
The ends and the sand template need to be managed, on a regular basis. Proper
management of the geotube system should enable it to stabilize the Coastal Bank for
a long time period.
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4. The beach will become a continual construction site, requiring its own
bulldozer.
The construction, regular maintenance and post erosion event maintenance occurs
during the “off season,” generally during the late fall and winter months.
Review of work logs show that the majority of sand template maintenance work
occurs during the “off season,” i.e. late fall and winter. This work involves
delivering and placing sand on the template before the storm season. Template
maintenance during the storm season – re-covering geotubes is required after storms
when the tubes are uncovered. In some years this can be 4 or 5 times, with the re-
covering process taking one or two days for each erosion event. In some years, the
current year is a good example, this may occur only once or twice. Over the past 5
years, there has been no need for maintenance during summer months, so during
the primary “beach” season there is no sense that this project is a construction site.
SBPF has acquired the dedicated use of a bulldozer to expedite sand template
management after storms based on “lessons earned” during the 2018 storm season.
5. There are reasonable alternatives to hard armoring almost 4,000 feet of beach.
Numerous alternatives have been examined and proposed over the past two
decades. This is the feasible alternative that meets applicable performance
standards, minimizes impacts, and allows for its removal, if needed.
The review of alternatives was presented in the NOI and subsequent submissions,
see the October 1, 2018 Public Hearing presentation and correspondence dated
November 2, 2018.
Numerous alternatives have been evaluated in theory and practice over the past two
decades including:
♦ Managed retreat (house moves): 17 houses on the 22 lots on the east side of
Baxter Road between 55 and 119 Baxter Road have been moved off the lot or
further away from the Coastal Bank on the same lot (these include house nos.
119, 117, 115, 109, 105, 101, 99, 97, 93, 87, 85, 83, 77, 73, 71, 67, and 55
Baxter Road).
♦ Coir reinforced coastal terraces: (DEP File No. SE48-1659, February 2004) were
installed but have not been effective for intense storm events.
♦ Beach dewatering: (2000 to 2009) yielded inconsistent results.
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♦ Drainage wells: (DEP File No. SE48-1773, February 2004).
♦ Beach nourishment: (EOEA No. 13468, 2006 / 2007) proposal was denied.
♦ Marine mattresses and gabions: (DEP File No. SE48-2395, 2010 / 2011)
proposal was denied.
♦ Revetment project: (DEP File No. SE48-2581 – July 2013) NOI was withdrawn
after a settlement was agreed upon allow the geotube project to proceed
(authorized per SOC SE48-2610 and OOC SE48-2824).
Soft Structures have not been considered
Several of the alternatives listed above included “soft structures” or non-invasive
measures. Those alternatives have not been adequate to protect the Coastal Bank
from erosion during large and sequential storms as demonstrated by their failure in
the winter of 2012-2013.
Homes can be relocated into the public roadway.
This was done in one case at northern Baxter Road enabling the owner to gain 10-
20 feet of additional distance from the bluff edge. This additional space might add
as little as a year or even less in an active storm season. This is not a reasonable
solution to the erosion problem along the length of the Baxter Road.
Shovel ready plans for Relocation of Baxter are now in place.
See Clarification Response #2 above. The easements for this access is only
available if the Town continues to support the project, and are not available were
the Town to withdraw the support it has provided to date in the form of a permit
and permission to use Town land for the Coastal Bank protection project. The
access is made available so that if the system fails from an engineering standpoint
and must be removed, or if it not maintained by the applicant, then the Town has
the right to exercise its spring easements and install the access. This should not be
confused with a relocation of Baxter Road however. The access would provide
emergency access to otherwise stranded houses and the lighthouse.
The Town has recently voted to allocated planning funds to explore the complete
relocation of Baxter Road.
The idea that Baxter Road should be relocated despite a successful privately funded
effort to make its relocation unnecessary makes very little sense from a community-
wide perspective. Relocating Baxter Road south of bayberry is going to be a very
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difficult proposition given the existence of homes on both sides of the road with
combined assessed values in excess of $350 million. Having contingencies plans in
place is reasonable. Abandoning a historic community when there is viable
alternative may satisfy a few, but it is not in the public interest.
This is not just any beach, it is historic and should be a marine sanctuary.
As climate change and sea level rise become a more central issue to Nantucket’s
survival, the idea that human beings should retreat and abandon their homes and
communities when there is viable way of preserving them is not a reasonable or
responsible position for public policy. Nantucket and other coastal communities
need to determine criteria for what can and should be protected. Any logical
approach to this is likely to result in a decision to protect Baxter Road and the
Sconset community. The geotube project is a pioneering, environmentally
responsible, privately funded effort that can stabilize the Sconset Bluff and from
which we can all learn. Furthermore, the affected homeowners have rights under
both State and Local law to protect their historic homes and the infrastructure
needed to live in those homes. This has been demonstrated on multiple occasions
in recent years by vote of both the Commission and through decision by the
Massachusetts Department of Environmental Protection (“MassDEP”).
NANTUCKET LAND COUNCIL COMMENTS
1. Performance Standards have not been met for Coastal Bank and Coastal Beach
The Expanded Project was designed and will maintained in accordance with the
applicable performances standards in the Massachusetts Wetlands Protection
Regulations (“State Regulations”) [310 CMR 10.00 et seq.] and the Town of
Nantucket Conservation Commission Wetland Protection Regulations (“Bylaw
Regulations”).
The review of performance standards in the State Regulations and the Bylaw
Regulations has been presented previously, see the NOI (Section 5 Regulatory
Consistency) dated January 5, 2018, the September 1, 2018 Public Hearing
Presentation, and correspondence dated November 2, 2018 for comprehensive
reviews of the relevant Performance Standards for Coastal Bank and Coastal Beach.
Responses specific to the eligibility of buildings / structures and public infrastructure
have been submitted previously, see correspondence dated November 16, 2018,
November 30, 2018, March 1, 2019, March 22, 2019 and April 19, 2019.
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2. Eligibility of homes as pre-1978 structures
All of the homes are eligible for protection as pre-1978 homes pursuant to the State
Regulations, and all but two homes are eligible for protection as pre-1978 homes
pursuant to the Bylaw Regulations
This topic has been addressed previously. Review of Nantucket Building
Department files documents the eligibility of all but 2 homes pursuant to the Bylaw
Regulations, and all the homes are eligible for protection pursuant to the State
Regulations. See correspondence dated November 16, 2018, November 30, 2018,
March 1, 2019, March 22, 2019 and April 19, 2019.
3. Waiver Request
The waiver request and support is included in the NOI.
A waiver request is included in NOI Section 5.3 for any lot which contains a
structure the Commission may determine is not eligible for protection either
because it does not contain a pre-1978 structure defined by Bylaw Regulation
(which we identify only as Lots 69 and 81), or installation of the geotubes across a
lot not deemed needed to protect public infrastructure.
4. Sand sediment source needs to be identified before work begins
This is a pragmatic and self-fulfilling comment, because before construction of the
geotube system and sand template begins the SPPF will need to secure a sand
source for its construction.
SBPF complies with the OOC special conditions to place compatible sand on the
template and will continue to comply with special conditions that require notifying
the Commission of sand sources and documenting compatibility of mitigation sand
with sand on the Coastal Beach seaward of the template, before placing sand on the
template.
APPLIED COASTAL RESEARCH & ENGINEERING, INC. COMMENTS
1. Gap lots have a specific meaning and designation does not require construction
of a CES across a gap lot.
Please see the legal analysis prepared by Rubin and Rudman, and the memorandum
from the Epsilon Associated dated May 14, 2019 submitted to the Commission
under separate cover.
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2. Erosion rates and mitigation sand volume is not appropriate
The method of determining Coastal Bank erosion and the related matter of sand
mitigation volume, follows the well-established method used by DEP and CZM, and
to which the Commission’s peer review concurred.
This topic has been discussed on numerous occasions, see correspondence dated
November 2, 2108, November 16, 2018, November 30, 2018, January 4, 2019,
February 7, 2019, March 1, 2019 and March 8, 2019. The commenter continues to
make this assertion without citing any specific data to propose an alternative
sediment contribution rate. As has been presented the length weighted average
annual contribution rate of the bluff in the Expanded Project area is 7.7 cy/lf/yr (and
the length weighted average annual contribution rate is 8.8. cy/lf/year for the bluff
from 55 to 119 Baxter Road) using a 20 year record which includes the large
erosion event of 2012/2013. The proposed mitigation protocol calls for having in
place 22 cy of sand per linear foot of template at the beginning of each storm season
(2.5 times the annual average contribution rate).
We also note that during review for an earlier alternative to protect the Sconset Bluff
from erosion (memo dated December 16, 2003 from John Ramsey to the Nantucket
Land Council), Applied Coastal Research & Engineering, Inc. (“ACRE”), commented:
1. Landward migration of the shoreline should approximately match landward
migration of the bluff.
2. For that 2,200 linear foot by 76 foot high coir terracing project, ACRE suggested
an annual mitigation rate of 21,080 cy of sand per year, which correlates to 10.4
cy/lf/yr, and that annual volume would adequate to replace the bluff as a
sediment source.
3. An annual sand mitigation volume of 21,080 cy/yr (10.4 cy/lf/yr) is an ample
volume of sand to maintain the beach / bluff system.
For this Expanded Project, ACRE now argues that: 1) bluff retreat is not an adequate
estimate of shoreline retreat, and 2) having 22 cy/lf on the template for mitigation is
not an adequate volume of sand to maintain downdrift landforms. These statements
are contrary to their earlier assertions.
3. Sand contributed off the template during storms is an important input to the
littoral system to transport sediment to protect downdrift landforms.
SBPF and their project team concur that sand contributed off the template and into
the littoral system is needed to maintain downdrift landforms.
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SBPF concurs that sand contributed off the template during storms is important, and
all of the sand contributed off the template occurs during storms. What we have
stated throughout this Public Hearing is that sand is contributed off the template
early in the storm cycle. The sand eroded off the template is deposited on the beach
in front of the template, and while on the beach the remains available during later
portions of the storm cycle. After the storm subsides, the exposed geotubes are re-
covered so that sand will be available for contribution to the littoral system during
the next storm. That total volume of sand available on the template to be
contributed to the littoral system (22 cy/lf/yr) far exceeds the length weighted
average contribution rate off the Coastal Bank.
In summary, 1) the proposed sand mitigation protocol contributes sediment to the
littoral system during storms, and 2) the volume of sand available on the template
exceeds that contributed off the unprotected bluff such that an ample volume of
sand is available to maintain downdrift landforms.
4. Other projects are not this large.
The applicable laws and regulations apply to all projects regardless of size. By way
of reference, the Town of Chelmsford recently completed construction of a 3,950
l.f. bank stabilization project on the Merrimack River.
The Wetlands Protection Act [M.G.L. c. 131, § 40] (the “Act”) and, Section 136-7 of
the Town of Nantucket Bylaw for Wetlands (“Wetlands Bylaw”) apply to all projects
regardless of size. The Performance Standards can scaled as needed to
accommodate all ranges of projects. This is a large project however, the rate of
sand mitigation established and the results of monitoring (that have shown no
adverse effect to adjacent Coastal Beaches) over the past 6 storm seasons provide an
entirely reasonable guide for Special Conditions that can be applied to the
Expanded Project.
5. This project can’t disadvantage other properties
The project purpose is the protect properties along the Sciasconset Bluff from
damage due to erosion.
The commenter provides no evidence whatsoever of damage to adjacent properties.
The basic project purpose is to protect the stability of the Coastal Bank in order to
protect 17 existing homes (properties) and public infrastructure from loss or damage
from erosion of this Coastal Bank. This is consistent with the Act and Wetlands
Bylaw. The Preamble to the Coastal Banks in 310 CMR 10.30(1) reads in part:
Nantucket Conservation Commission 16
Re: DEP File No. SE 48-3115
May 16, 2019
Coastal banks, because of their height and stability, may act as a buffer or
natural wall, which protects upland areas from storm damage and flooding
[emphasis added]. While erosion caused by wave action is an integral part of
shoreline processes and furnishes important sediment to downdrift
landforms, erosion of a coastal bank by wind and rain runoff, which plays
only a minor role in beach nourishment, should not be increased
unnecessarily. Therefore, disturbances to a coastal bank which reduce its
natural resistance to wind and rain erosion cause cuts and gullys in the
bank, increase the risk of its collapse, increase the danger to structures at the
top of the bank and decrease its value as a buffer.
The Preamble also reads in part:
When issuing authority determines that a coastal bank is significant to storm
damage prevention or flood control because it supplies sediment to coastal
beaches, coastal dunes or barrier beaches, the ability of the coastal bank to
erode in response to wave action is critical to the protection of that interest(s).
When the issuing authority determines that a coastal bank is significant to
storm damage prevention or flood control because it is a vertical buffer to
storm waters, the stability of the bank, i.e., the natural resistance of the bank
to erosion caused by wind and rain runoff, is critical to the protection of that
interest(s). [emphasis added]
SBPF acknowledges that this Coastal Bank is both a vertical buffer to storm waters
and a sediment source to downdrift landforms, and that the applicable sections of
the regulations are found in 310 CMR 10.30(3)(a). As discussed above and
throughout this Public Hearing process we have demonstrated the Expanded Project
meets the Performance Standard for 310 CMR 10.30(3)(a) and the applicable
sections of the Bylaw Regulations, see above.
The Expanded Project is an extension of the initial nearly 1,000 liner foot geotube
system for which there has been extensive monitoring performed. That monitoring
data has:
1) shown the geotube has been effective at protecting the interests of storm
damage prevention by stabilizing the Coastal Bank (i.e. maintains it function as
vertical buffer to storm waters); and
2) that the sand mitigation program has effectively contributed sand to the littoral
system to serve as sediment source to maintain down drift landforms (i.e.
continues to serve as a sediment source because sand is eroded off the face of
the template, and sand is replenished for future erosion events).
Nantucket Conservation Commission 17
Re: DEP File No. SE 48-3115
May 16, 2019
Conclusion
In closing, we have demonstrated throughout this Public Hearing process that: 1)
the Expanded Project meets all applicable performance standards in the State and
Local Regulations, 2) the Existing Project has not damaged adjacent properties, and
3) in fact the Existing Project continues to maintain adjacent Coastal Beaches
consistent with the portions of the nearby natural unprotected bluff. For the Existing
Project the Commission and MassDEP had to make a permitting decision based on
science, and engineering design parameters. With 6 storm seasons worth of
observations and data, the Commission can observe there have been no adverse
effects to neighboring properties or adjacent Coastal Beaches, and the Commission
therefore can make a permitting decision based on science, engineering design
parameters and direct observation.
We respectfully request that the Nantucket Conservation Commission close the
Public Hearing and issue an Order of Conditions allowing the proposed Expanded
Baxter Road and Sconset Bluff Storm Damage Prevention Project to be built, and
establish pragmatic Special Conditions consistent with those issued for the Existing
Project (SE48-2824) to protect the Interests of the Act and the By-law.
Sincerely,
EPSILON ASSOCIATES, INC.
Dwight R. Dunk, LPD, PWS, BCES
Principal
encl: Memo Dated December 16, 2003 from John Ramsey to the Nantucket Land
Council
cc: MassDEP-SERO
J. Posner, SBPF
A. Gasbarro, Nantucket Eng. & Survey
S. Cohen, Cohen & Cohen Law, PC
G. Wood, Rubin and Rudman, LLP
G. Thomson, W.F. Baird & Assoc.
L. Smith, Epsilon
R. Hamilton, Woods Hole Group
WHGJ between 1994 and 2003. The average shoreline change in the project area (as defined by
WHGI) is -9.7 feet per year. Over the Jong-term, landward migration of the shoreline should
approximately match landward migration of the bluff. However, using the WHGI shoreline erosion
information since 1994 would indicate nearly four (4) times the erosion rate proposed in the Epsilon
Associates letter. Due to the over-steepened nature of the Sconset bluff, perhaps the recent
measurements made by Frank Fessenden underestimate true bluff erosion rates, especially since
his results show substantial variability (±100% of the mean). If the project proponent is truly
attempting to mitigate for bluff erosion, the most conservative estimate would be to utilize the WHGI
shoreline change data. At a minimum, the bluff erosion rate proposed by Dr. Rosen should be used
(-3.7 feet per year).
Table A: Shoreline Change Rates along the Project Area between November
1994 and June 2003 (from Table 7 of the most recent SBPF sponsored
monitoring report prepared by Woods Hole Group, Inc.)
Station Shoreline Change (feet) Annual Change Rate (ft/yr)
89.2 -122.6 -14.3
89.5 -122.8 -14.4
89.8 -125.1 -14.6 -
90 -115.8 -13.5
90.6 -98.6 -11.5
91 -73.7 -8.6 ·-----. -----------.--
91.5 ' -38.1 -4.4 j .
92 i -16.1 -1.9
92.5 i -33.5 -3.9
Average -82-9 -9.7
'1
J
For several previous permit applications, the SBPF and/or their consultants have proposed
to mitigate only the portion of bank material that matches the four beach berm samples collected by
Dr. Rosen in 1998. Dr. Rosen's limited analysis determined that 44.5% to 46.5% of the bank
material matched the material found on the adjacent beach; however, it also determined that
approximately 92% of the bank material is sand or gravel. Although Dr. Rosen feels that finer sand
or coarser sand/gravel would be "Jost" to the downdrift beach system, there is no evidence of this
process. From a coastal processes perspective, all of the sediment eroded from the coastal bank is
important to downdrift shorelines. However, from the perspective of regional beaches and dunes, all
material that is sand-sized or coarser is important lo downdrift coastal resource areas. Therefore, al
a minimum, at least 92% of the bank-derived material is compatible with downdrift beaches/dunes.
Dr. Bruno's opinion that all bluff-derived material is "in essence ... lost to the nearshore zone"
is not supported by any facts or the work of previous researchers on this topic (e.g. Geise and
Aubrey, 1990). During the MEPA review of the Geotubes FEIR, Applied Coastal made the following
comments regarding Dr. Bruno's opinion:
2
"Sediment is mobilized from the bluff only during major storms, when it is lost to the
nearshore zone due to the local unusually steep beach slope and the high velocity
alongshore current system."
On p. 2-7, it is acknowledged that this claim is based on an opinion from one of the
applicant's experts. In addition, this same expert surmised that "the sediment accreted
along the dewatered beach Is not lost to the littoral system. Rather, it is still accessible to
erosion, suspension, and subsequent downdrift transport during wave events having
sufficient erosive power (p. 10-27)." Based on these statements, wave forces during storms
will erode sediment from the bluff and carry this material (whether it is gravel, sand, or silt)
offshore; however, sand eroded from the dewatered beach during the same storm event will
supply downdrift beaches. How do the waves discriminate between bluff-derived and
beach-derived sediments? This contradiction needs to be explained.
No explanation was provided and the FEIR was withdrawn. The Epsilon letter indicates that "in
order to be more conservative, we have estimated the amount of bank sediment remaining on the
beach as 1 Oto 15% (not 0% as Dr. Bruno suggests) of the maximum amount of sediment with the
appropriate grain size." Again, there is no factual basis for the 10% to 15% estimate and the opinion
utilized to derive this estimate disagrees with the scientifically-based concept that the coastal bluffs
are the primary source of beach material (Geise and Aubrey, 1990). Based on regional coastal
geology, the most appropriate estimate is to assume 100% of the bank sediment remains within the
beach system.
As discussed above, if the coastal bluff is being lost as a sediment source, appropriate
mitigation should be at least 92% of the bank-derived material. Table B indicates the volume of
material needed to supply downdrifl beaches based on the three erosion rates provided by SBPF
and an assumed project length of 2,200 feet and a bank height of 76 feet. Even utilizing the
minimum estimate of bluff erosion (14,190 cubic yards per year), the actual volume of material
eroded from the bluff on an average annual basis is between 14 and 22 times the volume estimated
in the Epsilon letter (for the 990 yd3lyear and 660 yd31year estimates, respectively). Even the 2,000
yd 31year anticipated maintenance volume is less than 15% of the volume eroded annually from the
coastal bank, based on the lowest estimate. Therefore, the proposed mitigation volume indicated In
the Epsilon letter (2,000 cubic yards per year) will not provide long-term mitigation for bank
stabilization. If the coastal bluff is lost as a sediment source by construction of the proposed
terraces or other armoring measures, we recommend utilizing the long-term erosion rate proposed
by Dr. Rosen (-3. 7 feel/year) and the estimate that 92% of the material is sand or gravel for
mitigation calculations (right column of Table 8). This would indicate an annual mitigation volume of
21,080 cubic yards per year. Due to the excessive erosion of the beach since 1994 (based on the
WHGI monitoring data) and the subsequent over-steepening of the coastal bluff, this volume of
material will be required to maintain the beach/bluff system.
3
Table B: Volume of Material Derived from the Sconset Coastal
Bluff Based on Estimates Provided by SBPF Consultants
Bank-Derived Bank-Derived
Sconset Bluff Volume (based on Volume (based on
Erosion 100%ofbank 92%ofbank
Computation material) material)
Method yd'tyear yd'tyear i
Fessenden (-2.49 15,420 14,190 feet/year)
Rosen (-3.7 22,910 21,080 feet/year) . ..
WHGI (-9.7 60,070 55,260 feet/year) !
Reference
Geise, G.S. and D.G. Aubrey, 1990, "Temporal Variability of Bluff Erosion, Outer Cape Cod,
Massachusetts", Journal of Geology.
/
4
Correlates to:
10.4 cy/ft/yr - 9.6 cy/ft/yr