HomeMy WebLinkAbout44 SE48_3115 SBPF Response 03_05_19 NLC ACRE Ltr 03_08_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
March 8, 2019
Nantucket Conservation Commission Via Electronic Mail and U.S. Mail
2 Bathing Beach Road
Nantucket, MA 02554
Subject: Response to Comments from Applied Coastal Research and Engineering
dated March 5, 2019 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 the unsigned letter prepared by Applied
Coastal Research and Engineering, Inc. (“ACRE”) dated 05 March 2019 which
provides their opinion on the project assessment prepared by Mr. Greg Berman
regarding the Expanded Baxter Road and Sconset Bluff Storm Damage Prevention
Project (“Expanded Project”). For the record, we note the ACRE correspondence
was submitted after the 01 March 2019 deadline established by the Nantucket
Conservation Commission (“Commission”) for receipt of matters discussed during
the 11 February 2019 Public Hearing. Also for the record, note that the SBPF
response to comments was transmitted to the Commission on 01 March 2019 in
compliance with the schedule established by the Commission on 11 February 2019.
The applicant wishes to object to the continual practice on the part of NLC and their
consultant ACRE, and others of late submissions. This is an unfair practice that
impairs the applicant’s ability to prepare its responses and can result in the
appearance of ACRE’s assertions being unanswered. In addition, it unnecessarily
extends the Public Hearing process.
Throughout the Commission’s review process the SBPF and their consultants have
demonstrated:
1. The Siasconset shoreline is a dynamic coastline and subject to extreme erosion
that presents and imminent danger, resulting in the need to stabilize the Coastal
Bank.
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2. The homes and infrastructure qualify for protection by a coastal engineering
structure pursuant to the Massachusetts Wetland Protection Regulations and the
Town of Nantucket Conservation Commission Wetland Protection Regulations.
3. The proposed geotube system is the most appropriate stabilization measure for
this environment, and as designed serves both functions of a Coastal bank, those
being a) bank stabilization, and b) a source of sediment to the littoral system.
4. The ongoing shoreline monitoring data and the peer review both show that the
existing project has not harmed the environment, that the sand mitigation is
appropriate, and that the failure triggers are a sufficient fail safe.
5. The concerns raised about sand volume, timing, template design, return design,
and data collection have been addressed through the many Public Hearing
sessions and response to comment documents.
Therefore, in conclusion the applicant has demonstrated the Expanded Project
meets the regulations and performance standards for Coastal Bank and Coastal
Beach.
The unsigned ACRE letter to the Nantucket Land Council, Inc. dated 05 March 2019
presents no new information and once again reiterates past stated opinions without
project-specific facts to support those opinions, and they provide no reference to the
Massachusetts Wetland Protection Regulations or the Town of Nantucket
Conservation Commission Wetland Protection Regulations. The focus of ACRE’s
letter is their interpretation of the Mr. Greg Berman’s report, to which SBPF
provided a response dated 07 February 2019. Below are excerpts from the letter, in
italics typeface, and our response in normal typeface.
1. Mr. Berman agrees that the current geotube system has resulted in increased
erosional impacts on adjacent shorelines …
We do not see any text in Mr. Berman’s report to this effect. On page 7 Mr.
Berman’s text reads as follows: “If a geotube expansion is approved erosion will
continue in adjacent areas, as is occurring now with the current extent of the
geotube array. With erosion continuing to occur (or made worse) at the end of the
structure, …”
We agree that erosion is occurring, and expect it to continue, frankly that is why the
existing geotube array and the proposed Expanded Project are needed and
proposed, to stabilize the Coastal Bank. If it were not eroding this Project would
not be needed.
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Table 2 from our correspondence dated 04 January 2019 is reproduced below.
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
Review of Table 2 above, shows that 3 of the 4 Profiles adjacent to the existing
geotube system (2 north and 2 south) document accretion from October 2014 to
September 2018. 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.
This monitoring data contradicts the opinion that the existing geotube system is
causing increased erosion on the adjacent shoreline.
Regarding erosion being “made worse” at the end of the structure, as the
Commission knows from its previous reviews and discussions, adding end returns,
and extending them as needed, is designed to effectively manage the potential
impact of erosion in the locations where the geotubes terminate.
2. … the current design and mitigation protocols do not function as originally
portrayed by SBPF.
This statement is incorrect. The design functions to stabilize the Coastal Bank and
provide sediment to the littoral system, i.e. to meet the project purpose and need.
As described in our letter of 01 March 2019; the Expanded Project and Existing
Project are both designed as geotube arrays covered by sand so that the sand along
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the face of the geotube system will erode during storms and contribute sand to the
littoral system during storms. Mr. Berman notes. “This is a good feature of the
design as it provides sand to the littoral system during storms, as during storms is
when additional sediment in the nearshore would have the biggest impact on
preserving the upland and coastal resource areas.” [page 5] This design feature
meets the Coastal Bank performance standard to provide sediment to down drift
landforms. The geotubes serve as a buffer to storm waves to protect the Coastal
Bank from further erosion, an interest of the Act and Bylaw, and the basic project
purpose for the Existing and Expanded Project.
3. That change to the mitigation protocol will result in reduced volumes of
mitigation entering the littoral system, accelerating the erosive impacts observed
over the past 5-years …
This prediction that sand volumes will be reduced in the future is without merit.
This topic has been discussed many times throughout the Public Hearing process.
Our most recent response to Sand Supply Volume item 2.b) in our 01 March 2019
letter reads in part as follows: The proposed Template Sand Replenishment
Protocol is proposed to contribute the “right” amount of sand to the littoral system,
as termed by Mr. Berman. Review of the Template Sand Replenishment Protocol,
submitted 02 November 2018, shows that the template would contain a supply of
22 cy of sand per lf of template at the start of each storm season. Exposed geotubes
would be re-covered after erosion events, with no maximum sand volume
established. Should additional sand be needed during a given storm season to
cover exposed geotubes, i.e. more than 22 cy/lf is used, then more sand will be
imported to comply with the re-covering requirement.
See response to item #1 above and Table 2 (reproduced above) and in our
correspondence dated 04 January 2019 which shows that the adjacent shoreline is
not experiencing accelerated erosion.
4. SBPF has over 20-years of data relative to the retreat of the MHW line but
utilized the bank retreat rate which lags in response until the bluff slumps.
First, the shoreline monitoring by the Woods Hole Group monitors the mean low
water (“MLW”) contour not the MHW contour.
This topic regarding the MHW retreat vs. Coastal Bank retreat was addressed in our
correspondence dated 07 February 2019, see response to item #2, on pages 3 and
4. I also refer you to the response to item #3 in that same letter which reads; The
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regulations require that the mitigation volume compensate for the loss of the
sediment source from the Coastal Bank that would otherwise be contributed to the
littoral system if the protection system were not in place. Therefore, the use of
Coastal Bank recession rate is the most applicable as compared to the recession rate
at MHW. The process of Coastal Bank erosion involves toe scour which leads to
over steepening of the banks, then at a certain slope the bank is too steep and it
erodes en mass. Over a long period of time the toe recession rate and the top of
bluff recession rate are essentially congruent. Therefore, the method used for the
proposed Project accurately presents Coastal Bank recession rate.
5. … SBPF’s monitoring data from the quarterly reports clearly show an increase in
erosion since the initial geotube system was installed.
This has been asserted many times during the Public Hearing without reference to
the dataset in the record. As described in several previous submittals, including two
of our most recent letters those dated 04 January 2019 and 01 March 2019, this
statement is not supported by the monitoring dataset. The quarterly surveys report a
dynamic shoreline documenting erosion and accretion over various periods of time
and portions of the shoreline. See the Southeast Nantucket Beach Monitoring, 77th
Survey Report dated September 2018 (“77th Survey Report”) which documents the
variations is shoreline change over time.
6. Mr. Berman’s review highlights the importance of calculating, the “right”
compensatory nourishment volume and requiring that volume be put down
every year as a minimum and then additional sand would be required to
maintain the cover on the geotube revetment.
We concur that the “right” volume of compensatory mitigation sand be placed on
an annual basis and we believe the proposed adaptive sand management program
meets this standard. See our response to item #5 in our 07 February 2019
correspondence regarding this topic.
As we have stated previously, should the Commission choose to establish a
condition that requires a minimum volume of sand be placed on the template after
each storm season we suggest the minimum volume approximate the calculated
Coastal Bank contribution rate, i.e. about 9 cy/lf/yr. A special condition regarding
minimum template replenishment volume might read to the effect: “the annual
minimum volume of sand placed on the template shall be 9 cy/lf/yr, or the
measured loss of sand volume off the template, whichever is greater;” the SBPF
would be open to such a Special Condition.
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7. The height of the bluff within the project area is the highest along the eastern
shoreline, which means for every foot of erosion a larger percentage of sediment
is contributed to the littoral system. The project area also has the highest rate of
erosion, thus providing more sediment to the littoral system then other areas
along the eastern coastline.
We are fully aware of the height of the Coastal Bank along this reach of shoreline.
As we have stated many times, and confirmed by Mr. Berman’s review, the formula
to determine the Coastal Bank sediment contribution rate is:
Coastal Bank Length x Coastal Bank Average Height x Erosion Rate = Nourishment Volume
Our calculations account for: 1) the height along this reach of shoreline, and 2) the
erosion rate (which includes the massive erosion observed in 2012/2013 along
portions of this Coastal Bank) to establish the project-specific nourishment volume.
Therefore, our calculations identify a large volume of sand (length weighted average
of 8.8 cy/lf/yr) is contributed off the Coastal Bank for this 3,820 lf of Coastal Bank
for the Expanded Project. The correlates to 327.6 cf/lf of Coastal Bank a large ratio
of volume of sand to length of Coastal Bank, or a total volume of 33,616 cy per year
for this length of Coastal Bank. By contrast storing a stockpile of 22 cy/lf/yr of sand
on the template to nourish the littoral system can provide a minimum of 84,040
cy/lf of sand during the storm season. This factor of safety accounts for the height
and retreat rate along this reach of Coastal Bank.
8. The mitigation template has been designed by the Applicant to provide 2.0 CY
regardless of the magnitude and duration of a storm and is not replenishable at a
rate to address back to back storms.
This statement is false. As described and depicted in our 16 November 2019
correspondence the sand volume on the face of the template is 6.2 cy/lf. Therefore,
for the Expanded Project each erosion event would contribute up to about 6 cy/lf, or
about 70% of the average annual un-protected Coastal Bank contribution rate per
erosion event. The correlates to 140% of the annual average rate for two erosion
events or 210% of the annual average rate for three erosion events. In addition the
ramps at each end of the system provide approximately 1,000 cy of available sand
that can wash away in a large storm.
There is no design or management intent to meter out only 2 cy/lf of sand. That
number was presented on our 06 February 2019 “Storm Memo” (attached to our 07
February 2019 correspondence) in which we described that even during the intense
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storm season in March 2018 with sand placement logistical challenges, the SBPF
contributed approximately 2 cy/lf of sand per storm event in compliance with
Special Condition 23.b (SE 48-2824).
Further, while this project goes to great lengths to make sand available for each
storm through the year, it should be noted there is no requirement in the
Regulations to do so, and no other Coastal Bank stabilization projects we are aware
of does this. There are obvious practical limitations of contributing sand at the
precise time during each storm when they come back-to-back, and the applicant’s
coastal geologist and engineer explained why the precise timing of sand
contribution is far less important than the annual volume contributed off the sand
template.
9. SBPF has made design changes to increase the depth of the toe of the geotube
revetment. However, as mentioned above no design changes have been made
to the compensatory mitigation design and protocols (except reducing the
annual contribution through adaptive management).
The Expanded Project design only needs minor changes relative to the Existing
Project to continue to meet the project purpose and performance standards. This
point is depicted succinctly in the time series diagram presented on page 5 of Mr.
Berman’s report. Without the project in place, time series diagram to the left, the
Coastal Bank will retreat landward and that will result in the loss of homes and
public infrastructure over time. The time series diagram to the right shows that sand
is washed off the geotubes during storm, the geotubes stabilize the toe of the
Coastal Bank, and prevents the landward retreat of the Coastal Bank. Thus, the
geotube system protects homes and public infrastructure. This design meets the two
function of this Coastal Bank, 1) it is a sediment source, and 2) it protects the
stability if the Coastal Bank. Thus, after five years of monitoring a new design is not
needed.
As discussed many time previously, see our most recent correspondence dated 07
February 2019 and 01 March 2019, the adaptive sand management protocol is
proposed to contribute the “right” volume of sand to the littoral system and it
establishes no upper maximum of sand to be placed in any given year. The
requirement to re-cover exposed geotubes after erosion events will be established in
an Order of Conditions and the SBPF will work to comply with the Order of
Conditions as they have for the past 5 years.
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10. It is clear upon review and analysis of the SBPF’s data that the proposed geotube
system will have negative impacts on neighboring beaches and shoreline
properties due to the loss of sediment from the littoral system.
Once again, the commenter is predicting a future without basing that prediction on
observed data. The quarterly shoreline monitoring shows a dynamic shoreline, and
that data has demonstrated there is no evidence of accelerated erosion post-geotube
construction that exceed historic observations. As for adjacent beaches, see Table 2
above which is reproduce from our 04 January 2019 correspondence. In terms of
the beach in front of the existing geotube system, again shoreline monitoring has
documented a dynamic system which appears to be stabilizing within a band of
movement. As described in item 1. d) of our 01 March 2019 correspondence;
review of profile data in the 77th Survey Report fronting the existing geotube system,
Profiles 91 and 91.5, show significant accretion (greater than 20 feet) following the
erosion event in the winter of 2012-2013, then some loss over time as that large
sediment volume was washed into the littoral system. Then another period of
accretion (approximately 20 feet) from the large volume of sand off the template
during the winter of 2017-2018 and minor loss as that sand washed into the littoral
system. The shoreline in front of the existing geotube system appears to be
stabilizing within a defined band since 2007. Finally, as the data show, more sand
has been contributed annually from the existing geotube area than has eroded
historically from the bluff in this area or from the adjacent unprotected bluff. There
has been no deprivation of sand contributed to the littoral system, nor has data
indicated negative impact on the size of down drift beaches.
11. Questions “feasibility of maintaining the geotube revetment and meeting the
failure criteria…”
An important aspect of the applicant’s proposal is the inclusion of failure criteria. In
the event that the negative impacts to fronting and adjacent beaches actually occur,
a failure is triggered and the Order of Conditions provides the Commission with
strong remedies to correct the deficiency or order the removal of the geotube
system. In this way those who are convinced that this stabilization project cannot
work over the long term should be comforted that action can be taken at the
appropriate time. It should be noted that the same negative impacts were predicted
for the existing project before it was installed and, to date, have not occurred.
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Conclusion:
In closing, throughout this review process the applicant presented a consistent
description of the design and mitigation program, and how the Expanded Project
meets the regulations and performance standards for Coastal Bank and Coastal
Beach. In summary the record shows:
1. The Siasconset shoreline is a dynamic coastline and subject to extreme erosion
that presents and imminent danger, resulting in the need to stabilize the Coastal
Bank.
2. The homes and infrastructure qualify for protection by a coastal engineering
structure pursuant to the Massachusetts Wetland Protection Regulations and the
Town of Nantucket Conservation Commission Wetland Protection Regulations.
3. The proposed geotube system is the most appropriate stabilization measure for
this environment, and as designed serves both functions of a Coastal bank, those
being; a) bank stabilization, and b) a source of sediment to the littoral system.
4. The ongoing shoreline monitoring data and the peer review both show that the
existing project has not harmed the environment, that the sand mitigation is
appropriate, and that the failure triggers are a sufficient fail safe.
5. The concerns raised about sand volume, timing, template design, return design,
and data collection have been addressed through the many Public Hearing
sessions and response to comment documents.
With sea level rise and climate change becoming immediate realities that cannot be
ignored, our challenge will increasingly be about finding the environmentally
responsible methods to defend our coastal communities. This project is well-
designed to do just that in a manner that enables learning about what works and
what doesn’t work, and in a reversible, removable form if harm is eventually
detected. In spite of this, we recognize that some critics of this erosion protection
system would prefer that the laws and regulations governing this project be changed
to require retreat rather than appropriate protection of the built environment.
Nonetheless, current law clearly provides the rights that enable this project to be
built.
Compliance with the regulations and performance standards has been presented in
Public Hearing presentations and documented in written submittals. The Expanded
Project is the extension of the Existing Project which was acknowledged in the two
previous Orders of Conditions, SE48-2610 and SE48-2824, issued to construct,
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monitor and maintain the existing geotube system fronting 87 through 105 Baxter
Road. The Existing Project underwent rigorous review and was issued an Order of
Conditions (“Order”) to construct the geotube system and a second Order was
issued to add a fourth tier of geotubes, SE48-2610 and SE48-2824, respectively.
Issuance of those Orders documents the existing geotube system was deemed to
comply with the Massachusetts Wetlands Protection Act (the “Act”) (M.G.L. c. 131,
§40) and the Wetlands Protections Regulations (310 CMR 10.00 et seq.), as well as
the Nantucket Town of Nantucket Bylaw for Wetlands (the “Bylaw”) (Chapter 136)
and the Town of Nantucket Conservation Commission Wetland Protection
Regulations. Comparing these two project one observes: 1) there is essentially no
difference in design between the Existing and Expanded Projects; 2) a robust sand
mitigation is proposed for the Expanded Project, as was provided for the Existing
Project; and 3) shoreline monitoring to date has not documented damage to nearby
Coastal Beaches – therefore the Expanded Project meets the requirements of the Act
and Bylaw as the Existing Project does. We respectfully request that the
Commission 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
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