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HomeMy WebLinkAbout2013_8_8 SBPF Submission_201405230853376460BAXTER ROAD AND SCONSET BLUFF STORM DAMAGE PREVENTION PROJECT NOTICE OF INTENT RESPONSES TO QUESTIONS FROM NANTUCKET CONSERVATION COMMISSION ASKED AT PUBLIC HEARING ON JULY 30, 2013 Below is a summary of issues raised at the July 30, 2014 hearing for the above-referenced project, organized by topic. 1. Sand Mitigation a. Initial Sand Cover on Revetment: The Notice of Intent Engineering Plans included an initial veneer of sand on the surface of the revetment, although we noted in the NOI text in section 3.2.2 that sand is typically not placed on the face of revetments, but may be included for aesthetic purposes. We have decided that rather than placing the sand on the face of the revetment, we will place the sand mitigation both in front of and at the ends of the revetment. This revised approach will make the sand more available to adjacent beaches to mitigate the armoring of the coastal bank. Sand will be placed at the toe of the revetment in the form of a terrace or sacrificial dune and will extend approximately 300 feet at revetment ends to help prevent end scour. This sand cover mitigation will be added to the design plans which will be revised next week using recent LIDAR survey results. b. Sediment Budget: We will submit sediment budget information separately. c. Mitigation Calculation Using Coastal Bank Retreat Rate See response #2 to Applied Coastal memo d. What if sand mitigation isn’t sufficient and end scour occurs? SBPF will monitor areas immediately adjacent to the revetment to determine if end scour is occurring and if so, additional sand mitigation will be provided to abate the situation. Also, SBPF will continue to monitor the extensive existing shoreline monitoring transects to determine if the project is causing impacts to downdrift beaches. e. What if sand mitigation isn’t sufficient and toe erosion occurs? SBPF will monitor the beach elevation in front of the revetment to determine if excessive toe erosion is occurring. If SBPF engineers determine that toe scour is excessive either sand mitigation will be supplied or additional rocks will be placed in 2    front of the revetment. These will gradually sink into the beach and will augment the existing toe scour protection of the revetment. f. Long term Funding of Mitigation? Funding of construction and the ongoing mitigation and maintenance commitment would be funded by the creation of a betterment district, i.e. assessments on the properties on both sides of Baxter Road fronted by the revetment. 2. Inventory of Public Coastal Engineering Structures in Massachusetts At the last meeting we reviewed some of the results of the inventory of public coastal engineering structures in Massachusetts prepared by the Department of Conservation and Recreation, Division of Waterways. One of the Commissioners requested a copy of the inventory and we have sent Jeff Carlson a copy so it can be posted on your website. 3. What will happen if the revetment fails? The various modes of revetment failure were discussed at the last ConCom meeting and we reviewed how this project has been designed to not fail. Also, we discussed failure if the fronting beach eroded to the point where toe scour threatened the structure. We discussed a pre-emptive plan to provide additional toe protection by dumping boulders in front of the revetment to prevent failure by toe scour. 4. Why not Retreat Alternative? As Sara Alger stated retreat is usually treated as moving a house back on the same lot, not requiring  the acquisition of additional land.  Also the town has 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.  The Town is not planning for alternative access at the moment. The Town has entered into a MOU  allowing the SBPF to try to protect the road.  As Phase 3 of the MOU, SBPF has agreed to use its best  efforts to design and arrange for approval and legal releases to identify a viable alternative access.  The Town began the process of looking at relocating Baxter Road and utilities and it has stopped  working on it until it sees whether SBPF is successful.     3      5. Public Access? We have described that the beach may thin somewhat after the revetment is constructed and high water after storm events and before sand mitigation is provided may restrict access along the beach. However, SBPF has proposed additional public access including the following:  Walkway along the top of the revetment with stairs to the beach  Use of existing stairs from top of bluff to revetment walkway  Possible future stairs  Use of the existing bluff walk and possible future expansion These locations of public access are shown on the attached three public access figures. 6. Article on California Beach Fleas Sarah Oktay referred to an article that she added to the record entitled “Local extirpations and regional declines of endemic upper beach invertebrates in southern California” published in Estuarine, Coastal and Shelf Science (2013), http://dx.doi.org/10.1016/j.ecss.2013.06.017. This article focuses on two species of isopods (beach or sand fleas) that reside in the supratidal or high intertidal beach zones along the California coast. This particular study focused on their distribution between Santa Barbara and San Diego. The article indicates that various coastal urbanization activities have caused a reduction in numbers of these two species. Coastal urbanization includes activities such as large beach nourishment, beach grooming and coastal armoring that affects sediment supply to the beach. The armoring projects in the areas of this study typically do not include sand mitigation associated with them, thus these are not comparable to Sconset where sand mitigation is proposed. 7. Nantucket Land Council and Applied Coastal Research and Engineering, Inc. See the separate response to the NLC letter and Applied Coastal memo.