HomeMy WebLinkAbout2018-11-5ConCom Minutes for November 5 2018 adopted Mar. 25 2019
CONSERVATION COMMISSJQN TU, C K
SPECIAL PUBLIC MEETINGO'd 14 C L E F
2 Bathing Beach Road
Nantucket, Massachusetts 02554 2019 MAR 26 P
www.nantucket-ma.gov 3 J
Monday, November 5, 2018
4 Fairgrounds Road, Community Room — 4:00 p.m.
Commissioners: Andrew Bennett (Chair), Ashley Erisman (Vice Chair), Ernie Steinauer, David LaFleur,
Ben Champoux, Ian Golding, Joe Topham
Called to order at 4:03 p.m.
Staff in attendance: Jeff Carlson, Natural Resources Coordinator; Terry Norton, Town Minutes Taker
Attending Members: Bennett, Erisman, Steinauer, LaFleur, Champoux, Golding, Topham
Earlier Departure: None
Town Counsel: George Pucci, K&P Law. P.C.
Agenda adopted by unanimous consent
*Matter has not been heard
I. PUBLIC MEETING
A. Announcements
B. Public Comment — None
II. PUBLIC HEARING
A. Notice of Intent
1. *Sconset Beach Preservation Fund (SBPF) — 59-119 Baxter Road (49&48 -various) Area SE48-3115
Sitting Bennett, Erisman, Steinauer, LaFleur, Champoux, Golding, Topham
Recused None
Documentation Supporting documents and plans. PowerPoint® presentation.
Applicant Dwight Dunk, Epsilon Associates Inc.
Representatives Gordon Thomson, Baird Associates
Les Smith, Coastal Geologist Epsilon Associates Inc
Steven L. Cohen, Cohen & Cohen Law P.C.
Jamie Feeley, Construction Manager Cottage and Castle Inc
Josh Posner, 77 Baxter Road, Chairman'Sconset Beach Preservation Fund
Glenn Wood, Rubin & Rudman, LLP
Art Gasbarro, Nantucket Engineering & Survey
Public None spoke
Discussion Carlson —The discussion tonight will cover Sediment Transport and Sand Mitigation Next hearing will
address wild -life habitat and other issues.
Dunk — Overview of previous hearings: existing project, proposed project, compliance with performance
standards, protect pre-existing 1978 homes and infrastructure, and stabilize bluff.
Proposed Sand Mitigation Protocol summary: consistency with regulations and policy, adaptive management
protocol comparison existing versus proposed, dynamic littoral drift system, rate of shoreline change.
Thompson — Sediment Transport: cross -shore transport from top of bluff to base to offshore; longshore
transport movement of sediment north to south, diffusion increases longshore transport rate.
Cross -shore transport: movement on and off shore, landward is loss of the bluff, seaward between minus 25
& minus 35 feet; Nantucket doesn't have a marked movement between the winter and summer beach profiles;
reviewed profiles to the north and south from May 2017, October 2017, and May 2018.
Explained how longshore transport occurs and causes downdrift erosion and accretion; geotubes are to
protect the bluff from periodic loss. `Sconset Bluff provides sand into the system; that is the reason for sand
mitigation. Majority of longshore transport occurs in the wave breaking zone; in the swash zone, sand is
pulled from the beach and ultimately moves longshore.
Diffusion is caused by a bump in the shoreline and increases longshore distribution of sand at the geotubes.
Summary: overfilling in front of the tube system puts additional sand in the system.
Smith — Sand Mitigation: mitigation requirements, beach profile surveys, bathymetry profile surveys,
nearshore cobble/boulder surveys, and sand source.
Mitigation Requirements: project compliance per 310 CMR 10.30(3), best available measures as defined in
CMR 10.4, calculating mitigation volume per CMR 10.30(3), retreat rate 2.8 feet per year. We have greater
sand volume with the project. Provides the interest of storm damage prevention and flooding. SBPF funding
will provide a bulldozer to speed up geotube sand template repair.
Nantucket Performance Standard 2.05 B(1): protects infrastructure and pre -1978 homes.
Massachusetts Coastal Zone Management (CZM) Hazard Policy #1: this is only feasible alternative,
compatible sediment must be placed within the system within a reasonable time, and calculation of long-term
average erosion rate as well as short-term erosion rates.
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ConCom Minutes for November 5, 2018, adopted Mar. 25, 2019
Sand Mitigation: calculated sediment contribution of the existing versus the proposed: 22 cubic yards at the
beginning of storm the season; after storm erosion, will replenish the front of the tubes with sand from top.
Cited all projects between 1986 to 2016 and the mitigation volumes of those projects; noted those projects
were much smaller.
Beach Profile Surveys by Woods Hold Group (WHG): pre-geotube versus post-geotube; the cumulative
shoreline change from 1991 to present shows a net erosion at the bluff versus accretion at Squam area and
Codfish Park.
Bathymetry Profile Surveys by WHG out to 40 feet: stable since 2008 at the bluff and Squam, but a lot of flux
at Codfish Park. WHG findings: geotube minimal impact; sand volume can be reduced to offset long-term
sand; no adverse effects and is similar to historic trends.
Nearshore Cobble/Boulder: underwater video surveys, track -line map, percent of cobble at off -shore
transects, screenshots out to 700 feet from beach since June 2016. Findings: high -concentration of cobble
habitat off shore and it is not being covered by the sand mitigation.
Sand Sources: sand will come from Island and off -Island sand pits. Compliance with Massachusetts Wetland
Protection Act performance standards and Nantucket Wetland Bylaw Regulation performance standards and
CZM coastal hazard policy.
Dunk — Summarized presentation and template sand management.
Cohen — Closing remarks: this project is cast in a light of protecting the bluff or the houses. There is a right
to have a CES if you are meeting the standards; feels the proposal meets the State and local guidelines for this
CES. The question of whether or not the right kind of sand is being used, it isn't about the right sand, but to
have the right volume of sand in the right places. The sand being provided is both sufficient to meet standards
and to match nature as much as possible. Sufficient sand is being provided to meet the needs of a storm and
to keep the tubes covered. We will make available any additional information the commission requests.
Bennett — In the presentation, off -shore sites with 1-1 mitigation were identified; asked where those sites are.
Smith — Those locations are in the NOI.
Bennett — In volumetric change, asked if that included the bluff or just the beach.
Dunk — That's what WHG provided. They start at mean low water and work back.
Golding — Asked how much sand is on the front of the template.
Dunk — The standard is to have about 2-3 feet of cover over the tubes available at the beginning of storm
season; as it is exposed, the template is recovered with 2-3 feet of sand.
Erisman — Regarding the comment, `the volume of sand in the right places', you've taken an average but one
end might erode faster than another end; asked if that average could be adjusted to meet the higher erosion
area.
Dunk — That's where the adaptive management protocol comes into play.
Erisman — Asked if they will be able to keep data on what's being added to which areas.
Dunk — Yes, after an erosion event, there's an estimate of sand loss average so the volume can be
extrapolated to identify where sand is lost in a storm.
Steinauer — About the dozer, asked if they have qualified drivers on Island who can respond immediately.
Feeley — We do pre- and post -storm photos as a requirement of their reporting; that visually captures the
amount of sand loss. As for the qualified equipment operator, we do have a local operator who will run the
dozer and is also a mechanic. The dozer's primary use is for work on the geotubes.
Steinauer — He'd like to see the sand put on top of the tube then have a test run where you send the driver
out there to see how long it takes to push the sand down to cover the tubes.
Dunk — The proposal is to get the tubes recovered within 10 work days barring unsafe working conditions. If
worker safety becomes an issue, there will be consultation with Mr. Carlson.
Golding — Asked Mr. Thompson for elaboration on where the sand that would come from the bluff is
coming from.
Thompson — You have the portion on the dry beach which is not being transported; but when you overfill
the system, the material is moved off shore so that you have more sand in the offshore that is in the system.
The shoreline has been shifted seaward by the placement of the sand when it's covering the face of the tubes.
The sand is still there but now it's off shore. At the beginning of a nor'easter, the sand covers the geotubes,
during the storm it's pulled off shore where it provides sediment to the system then the sand starts to move
along the shore. The mitigation provides two linear feet of sand which is dissipating wave energy and waiting
in the system; normally only one linear foot of sand would be provided by the bluff
Golding — If the tubes weren't there in the final day of a storm, the waves would be pounding against the
bluff taking sand into the system; with uncovered tubes, that is not happening. From the layman's point of
view, the tubes aren't providing the necessary amount of sand.
Thompson — The geotubes are the last line of defense, you off -set the sand that would be contributed to the
system and put it in front of the last line of defense. That amount is based upon what would normally be
provided and you ensure more of that is in place before the event occurs. Pointed out that it takes sand
several years to reach the end of Great Point.
Steinauer — The year of Hurricane Sandy, 30 feet of bank was lost; that equals one cubic yard per cubic foot
of bluff. That's a lot of sand to have sitting off shore. One of his concerns is that you don't have near enough
sand for a stormy year, one that would take 30 feet off the bluff.
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ConCom Minutes for November 5, 2018, adopted Mar. 25 2019
Smith — The sand mitigation meets State requirements; we're putting out more sand than required. We are
finding the existing project is not causing adverse impact because we are providing almost three times the
amount of sand as would be provided naturally.
Erisman — Though fine sand it might be better for the system, the clay is better for some eco systems.
Smith — We are looking at this for flood protection.
Dunk — Over the last three years, there were variations in amount of sand provided off the tubes; this past
year saw 20.3 cubic yards per linear foot loss. For this past year, there was a net increase in volume of the sum
of the transects for the full proposed length. In term of grain -size analysis, the samples he looked at show the
grain size is compatible with a medium to courser size with some fine sand in there as well.
Golding — When we stipulated the grain size in the original NOI, we didn't cover other aspects. Asked if
there has been an analysis that has gone beyond grain size. To him it doesn't look like what's in the bluff.
Dunk — It's compatible in terms of grain size. Regarding the existing project, part of the monitoring is to
ensure the sand going into the system isn't adversely affecting the cobble habitat.
Feeley — When there's fine in the newly delivered sand, it looks browner than what's on the template or on
the beach. What he's observed is that after time it blends in.
Golding — Transect 9.5 and 9.6, asked if there are pictures of those.
Dunk — Those are WHG base -line transects.
Golding — Asked if there was any change in the cobble habitat over the years.
Smith — The cobble remained pretty consistent from year to year.
Bennett — The longshore transport would take sediment north and south then migrating out; he would think
the impact off shore of the project is minimal compared to farther down the beach. We didn't specify
transects farther along the beach; asked if that might be more indicative of moving sediment.
Thompson — Cross shore transport comes first, then there is the longshore movement We aren't advancing
the shoreline so the area being monitored is appropriate. He believes they are capturing everything possible
cross shore; won't see as much longshore. Farther north or south, the change is closer to the shoreline and
change off shore will be less obvious. Volumes and changes we're talking about are relatively small; we don't
have a very large seaward shift.
Smith — He did show the profiles on shore in Squam and Codfish Park. At Squam Road, we're seeing similar
symmetry off shore. The shoals off Codfish Park are unrelated to this CES.
Erisman — Asked how the swash zone might change with exposed geotubes; the wave velocity is reflected
back.
Thompson — During a large storm event, the breaking waves pull sediment off shore and increases the width
of the breaker zone, pushing it out. If the geotubes become exposed, there is runup on the tubes and energy is
dissipated. Wave reflection was included within the modeling; these curved tubes don't have as much
reflection as a vertical bulkhead or seawall; the long -shore transport moves farther off shore. The swash zone
is just run up and run down and sand movement is minimal; most sand movement occurs where the waves are
breaking. As waves get bigger, they break farther out.
Golding — NOI 2015 Condition 11 about micro-organisms on the beach and Condition 29 required sampling
of invertebrates. Going to the report, a one micro -millimeter sieve was used. He doesn't know why a 45
micro -millimeter sieve was used. The last report didn't mention micro organisms; asked what happened.
Dunk — Regarding reflection, part of the variable is the angle of the slope; the bluff face has a different angle
of reflection.
Thompson — In this case the geotubes are set back with a 7 -foot gap between them to create more of a beach
slope to reduce reflection and thus dissipate the wave energy. Another factor is the hardness of the face that is
being hit. There is a lot of variability involved such as the section of the geotube that's exposed. You end up
with a different angle, height, and energy.
Steinauer — Asked for an explanation of the physics of end scour.
Thompson — At the end of the structure there is a process called diffraction, waves bending around a hard
structure, or refraction which bends waves in. At the end of this structure there is diffraction. More sediment
is placed on the ends and the ends of the CES are turned both in to minimize diffraction.
Golding — Asked if what's happening at the end of Great Point is an example of end scour.
Thompson — Explained that what happens at the end of Great Point is a tidal effect, not a scour effect
Explained how scour is calculated into long -shore transport.
Bennett — The point was brought up to put sediment on lots adjacent to the project. Applied Coastal brought
that up. Asked if that was putting sediment on the returns or farther down the beach.
Dunk — SPBF's response to that suggestion was to put sand the ramp template that is introduced into the
system. Putting sand on adjacent lots would constitute excess sand.
Bennett — There was a suggestion to have engineered flaws built into the geotubes to provide sand into the
system when the template is gone.
Golding — Regarding the actual placement loss of beach for the length of the tube, asked how much beach
would be under the structure.
Thompson — We can get that acreage data to the commission. The graphic on page 45 of the PowerPoint®
presentation shows those calculations.
Bennett — Asked for questions from the public.
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ConCom Minutes for November 5, 2018, adopted Mar. 25, 2019
No questions or comments from the public.
Cohen — Requested a continuance to November 19, 2018
Next hearing Carlson — The next hearing is scheduled for November 19 to look at wildlife impact; question on
invertebrates could be included. The December 3rd hearing could be to review outstanding issues.
Motion Continued to November 19 by unanimously consent.
Vote N/A
Ill. PUBLIC MEETING
C. Other Business
1. Approval of Minutes: None
2. Monitoring Report: None
3. Enforcement Actions: None
4. Reports: None
5. Commissioners Comment:
a. None
6. Administrator/ Staff Reports:
a. We are looking at the proposed 2019 schedule; that will be sent to the commissioners in advance. Since the upstairs
room might not be available, we are looking to move meetings to the Community Room. To do that we need to move
the meeting day permanently to Thursday.
b. Site visits are not at 3 p.m.
Adjourned at 6:25 p.m. by unanimous consent.
Submitted by:
Terry L. Norton
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