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HomeMy WebLinkAboutNOI 3.19.2026P.O. Box 1319, Plymouth, Massachusetts 02362 617-529-3792 | www.ecrwetlands.com SUPPLEMENTAL INFORMATION MEMO TO: FROM: DATE: RE: Yarmouth Conservation Commission Stan Humphries, Coastal Geologist February 3, 2026 911, 921 Great Island Road, W. Yarmouth Environmental Consulting & Restoration, LLC (ECR) is providing an environmental impact review of the shore protection project proposed at 911 Great Island Road in West Yarmouth. Compliance with the Massachusetts Department of Environmental Protection Regulations and the Town of Yarmouth Wetlands Protection Bylaw Regulations, revised December 2016, is the central part of the ECR review. In addition, this review also provides findings for potential erosion impacts to the updrift property (921 Great Island Road). A Plan showing Proposed Stone Revetment Bank Stabilization prepared by Cape Cod Engineering, Inc.(CCEI), dated February 2, 2026, was included in this review. Existing Conditions The Site is located to the west of Great Island Road and is bordered by single family homes to the north and south with a vacant parcel located immediately to the south which is owned by the GIHA. Nantucket Sound is located further west just south of the entrance to Hyannis Harbor. The Site consists of a developed lot with one pre-1978 reconstructed dwelling surrounded by lawn, a parking area along the gravel driveway and a beach access path. The Site’s geology and soils include glacial and depositional materials consisting of Plymouth loamy coarse sand, 3 to 8 percent slopes, very stony and Nantucket sandy loam, 3 to 8 percent slopes, stony, that comprise the coastal beach and bank, respectfully. According to the MCZM shoreline change data, a majority of the western shoreline of Great Island is erosional (Figure 1). At the Site, there is a short-term (1970 to 2018) beach erosion rate of -1.14 feet per year as interpolated between two transects (Figure 2). However, bank retreat measurements taken by CCEI show a 1.6 ft. / yr erosion rate between 2015 and 2021 with measurements during the period 2021 to the present show the erosion rate to be approx. 2 ft./yr. Being adjacent to the Hyannis Ferry channel, wake-produced waves play upon the shoreline and may account for the difference between beach erosion rates and bank retreat rates. Coastal engineering structures along the western shoreline of Great Island, including stone revetments and stone groins, in particular, play a significant role in the overall configuration of the shoreline (Figure 3). In general, each groin has trapped beach materials on one side and deprived them on the other side. Revetments have been constructed between the groins to stabilize the shoreline and maintain the linear stretches. That is the goal of the proposed project. The steep portion of the coastal bank, ranging from ranging from 3 to 7 ft. in height, and the location of two large boulder erratics are also shown in the bottom figure of Figure 3. As shown in the attached sequence of three photos (Figure 4), these boulders play a role in beach erosion and bank retreat, particularly on the GIHA property. Boulder #1 appears to act much like a groin where one side (north in this case) is erosional and the other side is accretional. While the south side of boulder #1 is n ot accretional as much as it is simply less erosional, the retreating bank on the north side is much more P.O. Box 1319, Plymouth, Massachusetts 02362 617-529-3792 | www.ecrwetlands.com obvious. In summary, the fact that material is eroded from the bank just north of the boulders and deposited further north on the beach is supported by the attached Longshore Sediment Transport figure for Great Island (Figure 5). Permissible Shore Protection Options Cape Cod Engineering, Inc. presented three options for managing the shorefront erosion along 911 Great Is. Rd. in a letter to the Awad’s dated August 2, 2016. They included the following: 1. Create a cobble stone buttress for the fiber array in lieu of sand fill; 2. Re-create a low crested breakwater within the intertidal zone; and 3. Focus on the damaged scarp. Some form of stone revetment or riprap of an undetermined height and scope that could involve several options involving stone configurations, in combination with sand nourishment, was only generally mentioned at that time. Option 3 was permitted and implemented which consisted of a coir envelope and log array underlain by a geotextile filter fabric. The array has failed and been removed from the beach. In addition, the eroding coastal bank has extended further south than what the array was constructed to protect. As a result, CCEI is now proposing a longer and more protective solution to address the eroding bank. Since the existing dwelling was the reconstruction of a structure built prior to 1978, both the state and local wetland protection regulations allow for coastal engineering structures with certain conditions. Such regulations include the following: •State regulation 310 CMR 10.30(3) states that No new bulkhead, revetment, seawall, groin or other coastal engineering structure shall be permitted on such a coastal bank except that such a coastal engineering structure shall be permitted when required to prevent storm damage to buildings constructed prior to the effective date of 310 CMR 10.21 through 10.37 or constructed pursuant to a Notice of Intent filed prior to the effective date of 310 CMR 10.21 through 10.37 (August 10, 1978), including reconstructions of such buildings subsequent to the effective date of 310 CMR 10.21 through 10.37, provided that the following requirements are met: (a) a coastal engineering structure or a modification thereto shall be designed and constructed so as to minimize, using best available measures, adverse effects on adjacent or nearby coastal beaches due to changes in wave action, and (b) the applicant demonstrates that no method of protecting the building other than the proposed coastal engineering structure is feasible. (c) protective planting designed to reduce erosion may be permitted. •Town Section 4.05(3)(a)(1-3) has the same regulation with the following addition: (4) the applicant provides sufficient evidence that the building was constructed pursuant to a Notice of Intent prior filed before August 10,1978. Based on these requirements, CCEI has produced a Plan that shows an approximate 300-foot long, engineered stone revetment with the cap stone at elevation 11 feet. Concerns about end scour and collateral impacts are mitigated and improved from the existing conditions by a series of factors: 1. The revetment cross-section is reduced and tapered, terminating in a location where sand can readily be added; 2. This sand replenishment of targeted additions of sand fill can be added at that specific location as necessary, with a well-established delivery route currently in place; 3. The end location is a mid-point in a groin cell where sand replenishment is a part of the beach site stability program DEP File No. SE 83-2437, thus sand replenishment will predictably be on a routine basis or as specified by a monitoring program : and, 4. Recurrent sand fill of 40 c.y. is proposed within 25 feet of the south end of the revetment. -2- P.O. Box 1319, Plymouth, Massachusetts 02362 617-529-3792 | www.ecrwetlands.com Conclusion The shoreline along 911 Great Island Road consists of a coastal beach and bank composed of glacial materials exposed to an erosion rate of approximately 1-2 feet per year near the boundary of these two properties. A large boulder erratic, located on the GIHA property, forms a natural endpoint for this retreating bank. The failure of a coir array to protect the bank has led CCEI to propose a stone revetment that extends to the first boulder. Having demonstrated that another method was not feasible, a revetment similar to others constructed along this shoreline is permissible under the state and local wetland protection regulations. Since the proposal includes the annual placement of sediment that otherwise could be provided by the eroding bank, ECR believes the project will benefit both owners whose land will be protected from further erosion. Upon review of this coastal resources impact memo, please contact me at (617) 543-1654 or stan@ecrwetlands.com with any questions or requests for additional information. -3- Figure 1. Majority of the western shoreline of Great Island is erosional (red lines) with some locations showing no statistical change (yellow lines) or accretion (green lines). Figure 2 Figure below Escarpment Two large boulders Figure 3. Upon closer examination, the shoreline comprises three components that form similar cells. The components within each cell include a stone groin (yellow arrow); a linear stretch (blue line); and a curvilinear stretch (red line). Figure 4. During a five-year period from 2016 to 2021, the coastal bank receded more landward north of boulder #1 than it did between boulders #1 and #2, as shown by the length of the separate yellow arrows (Google Earth photos). Oct. 2016 Oct. 2018 Oct. 2021 Boulder #1 Boulder #2 Figure 5. The “Net Transport Indicator” indicates a consistent northerly transport along the west side of Great Island (WHOI Sea Grant, 2011). SITE 1 Notice of Intent Project Narrative 911, 921 Great Island Road, West Yarmouth SUMMARY The area subject to this Notice of Intent is a residential parcel of land on the west- facing shore of Great Island, West Yarmouth. Work activity is proposed in the following coastal wetland resource areas: Coastal Beach; Coastal Bank; Land Subject to Coastal Storm Flow, specifically a VE zone of elev. = 15 which terminates along the upper lip of the Coastal Bank; and Buffer Zone to Coastal Bank. The immediate work site subject to the NOI has had a 17 year history of erosion management, initiated in 2008 by installation anchored coir roll revetment, subsequent repairs / rehabilitation to that, removal of the remnants and sand nourishment activity. This NOI seeks to install a low crested stone revetment form of erosion management to replace the anchored coir roll revetment that failed despite efforts to maintain with sand cover and other necessary adjustments. EXISTING RESOURCE AREA CONDITIONS Much of the general evaluation of impacts to the listed wetland interests of the MA DEP regulations and Yarmouth Wetland By-Law contained herein is based on the understanding that the site is not a natural, unperturbed Coastal Beach or Coastal Bank, especially regarding the C. Beach. The status and functional value of existing stone groin structures create a long-term developed and progressing condition with observed beach stability in locations on the prevailing sediment collection side of the groins with a reach of beach with disadvantaged sediment levels on the lee sides of the groins. The subject site is one of the lee sides. Coastal Beach Condition – The nearby Coastal Beach currently contains a series of stone groins and the beach fronting the project area is within a closed “cell” framed by two substantial stone groins. The beach deposit is a collection of assorted glacial rubble stone, find grained quartz sand, pebbles and cobble in combination with the groin formations to the south and north. The manmade features are well established and appear on Mass Waterways License 197, issued in 1976. 1938 aerial images show the stone array of groins. The west-facing shoreline is subject to prevailing southwest winds, variable tide levels, storm tides and the wake actions caused by transiting vessels from the dredged channel of Hyannis Harbor. The interruption of long-shore sediment transport resulting from the groins is a factor in a lower beach deposit than the beaches to the north and to the south. This condition in combination with 2 the exposure of wind, tides, storm waves, and large vessel wake action during high course tides accelerated the erosion of the upland. Sediment doses provided by the applicant have provided a source of sediment, however sediment alone is not sufficient to slow the Coastal bank retreat accelerated by the low beach. The Coastal Bank Conditions The Coastal Bank is an open, steep, eroded scarp of varying height ranging from 3 to 7 ft. Concern for bank slope stability existed prior to 2008 and the coir roll revetment stalled erosion for approx.. 6 years. Concern heightened after 2015 and the bank retreat measurements since then show a 1.6 ft. / yr erosion rate between 2015 and 2021; measurements during the time period 2021 to the present show the erosion rate to be approx. 2 ft. / yr. Figure 1 – View of the Coastal Bank Eroded Condition prior to 2024 sand fill 3 Figure 2 – Recent conditions showing residual sand fill along C. Bank scarp in vicinity of existing beach stairs. THE PROJECT The applicant intends to install a stone revetment of a low crested form along the eroded scarp to replace the protection formerly provided by an anchored coir fiber roll revetment and to maintain the reach of revetment with annual sediment nourishment. The past 17 years of on -going management with sand deposits and other adjustments demonstrates very well the applicant’s commitment to appropriate mitigation for the proposed revetment feature. The past practice of providing sand cover for the anchored fiber roll revetment was not rewarded with stability and therefore is physically demonstrated as less feasible with respect to the targeted result. Comparatively, the installation of the stronger, more appropriate – for – the – exposure low crested stone revetment in combination with the same dedicated effort to provide mitigating sediment shifts the project into a category of being viewed as feasible for the intended result. 4 PERFORMANCE STANDARDS Coastal resource areas directly affected include: • Coastal Bank • Coastal Beach • Land Subject to Coastal Storm Flow (LSTCSF) Nearby coastal resources include: • Land Under the Ocean • Land containing Shellfish • Coastal Dunes The listed nearby resource areas are distant enough from the activity to remain unaffected by the work with adherence to appropriate work limits and work practices. No alteration of the nearby coastal resources is proposed. IMPACTS The directly impacted resources will be affected as follows: • The Coastal Beach sediment will be altered temporarily by small equipment activity of the scale of a mid-size excavator and front-end loader. • On-going beach sediment nourishment mitigation will be applied to the revetment face and will distribute with time and successive tidal inundation over the fronting beach deposit. • The Coastal Bank shall be impacted by inhibiting the less- than – natural erosion rate. Storm tide surges that exceed the stone revetment cap have potential to cause for occasional erosive action allowing for some bank erosion to continue. Coastal Banks -Sediment Source Banks (310 CMR 10.30) “WHEN A COASTAL BANK IS DETERMINED TO BE SIGNIFICANT TO STORM DAMAGE PREVENTION AND FLOOD CONTROL BECAUSE IT SUPPLIES SEDIMENT TO COASTAL BEACHES, COASTAL DUNES OR BARRIER BEACHES…..” “No new bulkhead, revetment, seawall, groin or other coastal engineering structure shall be permitted on such a coastal bank except that such a coastal engineering structure shall be permitted when required to prevent storm damage to buildings constructed prior to the effective date…” The site has been the subject of repetitive efforts to manage an anchored coir role revetment (DEP File No. SE83-1852). An Order of Conditions (DEP File No. SE83-2437) is currently in force for sediment replenishment. The existing building replaced an existing building that meets the date of August 1, 1978. The replacement construction endeavored to set the building back significantly from the C. Bank. An Order of Conditions was not issued for building construction. 5 Best Available Measures -(310 CMR 10.27 & 10.30) By examination of the overall coastal armor system along certain reaches of the great island shore with consideration for the wind and Nantucket Sound exposure, the behavior of the previous erosion management measures we arrived at a conclusion that best available measures can be interpreted as a low crested stone revetment with a textured face, tailored close to the bank scarp, appropriately terminated on the south with a small, low elevation cross section. Such a feature combined with the established practice of sediment nourishment mitigation combines to represent a proven best available measure. Concerns about end scour and collateral impacts are mitigated and improved from the existing condition by series of factors: 1. The revetment cross-section is reduced and tapered terminating in a location where sand can readily be added; 2. This sand replenishment of targeted additions of sand fill can be added at that specific location as necessary with a well-established delivery route currently in place; 3. The end location is a mid - point in a groin cell where sand replenishment is a part of the beach site stability program DEP File No. SE 83-2437 thus sand replenishment will predictably be on a routine basis or as specified by a monitoring program. The 17 year-long delivery of sand nourishment demonstrates three things: 1. Adding sand is a manageable practice and the applicant has the permit history and resources do that and, 2. Sand alone is insufficient for the protection of the building. 3. With the revetment installed and properly terminated, a more practical sand volume of sand will be applied and it can be placed where it will be most effective, burying the south end of the revetment and replenishing the beach on the south end within the cell. With the groin cell of Coastal Beach effectively isolated by the groins we have the opportunity to have the sediment mitigation more closely controlled and perceived impacts from revetment construction truncated. Several location exist along the cape Cod shoreline where sediment mitigation is faithfully pursued, municipally regulated and successfully maintain healthy beach deposits that front stone revetments. “WHEN A COASTAL BANK IS DETERMINED TO BE SIGNIFICANT TO STORM DAMAGE PREVENTION OR FLOOD CONTROL BECAUSE IT IS A VERTICAL STORM BUFFER TO STORM WATERS, 310 CMR 10.30(6) THROUGH (8) SHALL APPLY” The proposed project involves upgrading the concept pursued by the 17-year erosion management efforts. Those past efforts and the proposed efforts reflect the function of the Coastal Bank as a vertical storm buffer. 310 CMR 10.30(4) Any project on a coastal bank or within 100 feet landward of the top of a coastal bank, other than a structure permitted by 310 CMR 10.30(3), shall not have an adverse effect due to wave action on the movement of sediment from the coastal bank to coastal beaches or land subject to tidal action. The proposed activity involves access for material and equipment delivery within the buffer to the C. Bank. The placement of a more durable form of revetment with upper slope vegetation enhancement is proposed in scarped areas of the C. Bank intended as improvement to the C. Bank stability. It is accepted that strong storms with storm tides will continue to erode this C. bank thus delivering sediment to the beach and to the flood zone. Future reconstruction or renovation of the revetment is likely given the 6 relationship to the coastal flood zone and elevation. The summary relating to 310CMR 10.30(3) addresses mitigating sand supply relating to the bank value as a sediment source within the isolated groin cell. 310 CMR 10.30(5) The Order of Conditions and the Certificate of Compliance for any new building within 100 feet landward of the top of a coastal bank permitted by the issuing authority under M.G.L. c. 131, § 40 shall contain the specific condition: 310 CMR 10.30(3), promulgated under M.G.L. c. 131, § 40, requires that no coastal engineering structure, such as a bulkhead, revetment, or seawall shall be permitted on an eroding bank at any time in the future to protect the project allowed by this Order of Conditions. The building when constructed did not require an Order of Conditions. 310 CMR 10.30(6) Any project on such a coastal bank or within 100 feet landward of the top of such coastal bank shall have no adverse effects on the stability of the coastal bank. The access activity is specified to be in an area to be fortified and restored at the north end of the project area where the beach is highest. The access activity will not destabilize the bank once the project is completed. 310 CMR 10.30(7) Bulkheads, revetment, seawalls, groins or other coastal engineering structures may be permitted on such a coastal bank except when such bank is significant to storm damage prevention and flood control because it supplies sediment to coastal beaches, coastal dunes and barrier beaches. • The Project is proposing revetment on a Coastal Bank pursuant to 10.30 (30) 310 CMR 10.30(8) Notwithstanding the provisions of 310 CMR 10.30(3) through (7), no project may be permitted which will have any adverse effect on specified habitat sites of rare vertebrate or invertebrate species, as identified by procedures established under 310 CMR 10.37. • The Project is reviewed by NHESP. Previous projects were reviewed by NHESP. The mapped PH zone is on the north 50% of the project area where the land is more stable. We anticipate that with time of year restrictions adhered to and sediment replenishment activity also adhering to TOY restriction parameters there should be no significant adverse impacts. An NHESP comment summary is forthcoming. 310 CMR 10.27 Coastal Beaches The work area shall be limited and temporarily affected with anticipated recovery over several tide cycles following completion. Consequential impact is related to periodic sediment nourishment. WHEN A COASTAL BEACH IS DETERMINED TO BE SIGNIFICANT TO STORM DAMAGE PREVENTION, FLOOD CONTROL, OR PROTECTION OF WILDLIFE HABITAT, 310 CMR 10.27(3) THROUGH (7) SHALL APPLY: 310 CMR 10.27(3) Any project on a coastal beach, except any project permitted under 310 CMR 10.30(3)(a), 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. 7 The project is a project designed and intended to meet with the tenets of 10.30 (3) to the degree practicable. 310 CMR 10.30(4) Any groin, jetty, solid pier, or other such solid fill structure which will interfere with littoral drift, in addition to complying with 310 CMR 10.27(3), shall be constructed as follows: • This project, a portion of which is within the beach deposit does not significantly interfere with littoral drift because the revetment is close to the C. Bank scarp and runs parallel with the shore, minimizing seaward encroachment. (a) Shall be the minimum length and height demonstrated to be necessary to maintain beach form and volume. In evaluating necessity, coastal engineering, physical oceanographic and/or coastal geologic information shall be considered The sediment replenishment program is intended to be commensurate with a volume of sediment eroded from the bank on an annual basis. Based upon comparable projects with similar coastal exposure it is anticipated that the beach volume will be maintained adequately. (b) Immediately after construction any groin shall be filled to entrapment capacity in height and length with sediment of grain size compatible with that of the adjacent beach. • No groins are being constructed; Sand replenishment to the extent proposed will not succeed to fill the groin cell to entrapment. There will be an expected improvement to the beach elevation with time. (c) Jetties trapping littoral drift material shall contain a sand by-pass system to transfer sediments to the downdrift side of the inlet or shall be periodically re-dredged to provide beach nourishment to ensure that downdrift or adjacent beaches are not starved of sediments. • No alteration of a stone groin or stone breakwater is proposed. ALTERNATIVES SUMMARY The goal here is to provide “best available measures" for managing the on-going bank erosion. The context of the practical measures available relate to the assessment of the measures previously installed, observed effectiveness and impact as well as evaluation of nearby existing erosion management structures of an older age, and observed impacts in the vicinity of those structures. The intensity of the flood zone and storm exposure are factors as well. Factors for consideration include the durability of the coastal bank soil composition and capability for vegetive quality development. In addition to material choices and labels for a specific CES with certain classifications, e.g., stone revetment, seabag revetment, gabion revetment, vertical wall, anchored coir log revetments, etc., best available measures relate to variable parameters for design relating to the scale, size and height of the proposed measures applied. Any one of a collection of CESs can be of a graduated height, depth, mass extent, and texture within each alternate. In the current case, the applicant selects a modest height, mid-sized stone scale, textured faced stone revetment. Many alternatives could be offered that would intensify the extent, frequency and scope of work activity and alteration. The building qualifies as a pre-1978 structure and the existing groins are existing prior to 1978. The alternative review resulted in a summary of description of common shorefront protection 8 methods. A chart of considered alternatives is attached as an appendix. A work / task / equipment protocol is also attached as an appendix. Yarmouth Wetland Regulations The summary below is a review of the applicable portions of the Yarmouth Wetland Regulations. The Regulatory interests are: • Public or private water supply • Groundwater supply • Flood control • Erosion and sedimentation control • Storm damage prevention including coastal storm flowage • Water quality • Prevention and control of pollution • Fisheries • Shellfisheries • Wildlife habitat • Rare species habitat including rare plant and animal species • Agriculture and aquaculture • Resilience to climate change • Recreation values deemed important to the community. Of these interests the project has a relationship to: • Flood control – The project furthers the interest of coastal flood control by intending to protect the Coastal Bank with demonstrated sediment mitigation. • Erosion and sedimentation control – The project furthers this interest by inhibiting C. Bank erosion • Storm damage prevention including coastal storm flowage – The project furthers this interest by assisting to stabilize the C. Bank. • Fisheries – The proposed activity on the coast relates to fisheries interests however the impacts from the actual work shall be controlled and are temporary. The consequential impacts are consistent with the long- term site conditions. • Shellfisheries - The proposed activity on the coast relates to shellfisheries interests however the impacts from the actual work shall be controlled and are temporary. The consequential impacts are consistent with the long-term site conditions. • Wildlife habitat – The proposed activity represents a “status quo” condition with respect to the wildlife interests in the immediate area. A portion of the work zone mapped as priority habitat by NHESP. Map portion is included. The project represents a successive effort to upgrade cable – arrested coir fiber measures previously used for bank stabilization along the same reach of coastline. 4.02 Coastal Beaches Any activity which is allowed on a coastal beach or tidal flat or within 100 feet of a coastal beach or tidal flat shall not have an adverse effect on the coastal beach or tidal flat by: (a) Affecting the ability of the waves to remove sand from the beach or tidal flat • The existing condition of the C. Beach with mitigation measures will remain like current conditions. Sand nourishment has been ongoing. 9 • Modest wave forces with modest storm tides will exceed the revetment elevation and continue to remove sediment from the beach as well as deposit sediment. (b) Disturbing the vegetative cover, if any, to destabilize the beach or tidal flat • There is no vegetative cover affected. (c) Causing any modification of the beach or downdrift beach that would increase the potential for storm or flood damage; • The revetment will allow for improved bank stability and the established sediment program will effectively mitigate impacts within this closed stone groin cell. The long existing stone breakwater and groin system does affect the beach sediment interrupting the long shore littoral sediment drift so the cell is disadvantaged, but improved with sediment donations. (d) Interfering with the natural movement of the beach or tidal flat; • The existing wall features, stone breakwater and groin features are currently affecting the beach sediment. No significant change is proposed. (e) Causing artificial removal of sand from the beach or downdrift beach; No artificial removal of sediment is proposed. Artificial importing of sediment (mitigation) is proposed. (f) Removing seaweed or substrate from the coastal beach in the intertidal zone (between MLW and MHW) that provides valuable habitat and potential for sand accretion, unless deemed a public health emergency by the Director of Health. • Not applicable. 4.05 Coastal Bank The Yarmouth regulations appear to recite those of 310 CMR. 4.05(3)(a) No new bulkhead, revetment, seawall, groin or other coastal engineering structure shall be permitted on a coastal bank that provides significant sediment to an adjacent or downdrift coastal beach; except that such a coastal engineering structure shall be permitted when required to prevent storm damage to buildings constructed prior to August 10, 1978, including re-construction of such buildings subsequent to the effective date of these regulations, provided that the following requirements are met: Previous measures to stabilize the Coastal bank have been attempted. A cable-anchored, coir fiber form of revetment was permitted and in-place along the segment of coastline since 2008, steadily decaying until removed in 2018 with remnant removal recently. i. Coastal engineering structures or modifications thereto shall be designed and constructed to minimize, using best available measures, adverse effects on adjacent or nearby coastal beaches due to changes in wave action; 10 In this segment of coast, between two significant stone groin structures, the combined technical approach of the low crested stone revetment with established sediment mitigation will not cause for significant adverse impacts to the nearby beaches. Given the littoral sediment drift interruption, the mitigation assignment for the improved bank protection with sediment doses will minimize adverse impacts with a component of improved sediment supply and a reduction in the frequency of which erosion measures must be re-worked or replaced. ii. The applicant demonstrates that no method of protecting the building other than the proposed coastal engineering structure is feasible; • The concept of dwelling protection relates to the degree of threat. Degree of threat relates primarily to evalauytion by those most familiar with the threatening conditions. The erosion rate of the past three years is on the order of 3 to 4 ft. / yr on the south portion of locus and 1 to 2 ft. / year on the north. Previous technical measures that are common technical measures employed by experienced reputable ecologists have been installed, maintained for approx. 7 years and failed. The alternatives summary appendix lists alternatives to consider when reviewing “best available measures”. iii. Protective planting designed to reduce erosion may be permitted; and • Not Applicable, but the Project proposes planting designed to reduce erosion along the upper bank slope above the revetment. iv. The applicant provides sufficient evidence that the building was constructed pursuant to a Notice of Intent prior filed before August 10, 1978. – A dwelling in the approximate location as the existing dwelling existed prior to Aug. 1, 1978. The replacement building was shifted away from the coast to a meaningful degree. Erosion has accelerated since. (b) Any project on a coastal bank or within 100 feet of the top of a coastal bank, other than a structure permitted under section 4.05, (3), (a), shall not have an adverse effect due to wave action on the movement of sediment from the coastal bank to coastal beaches or land subject to tidal action or flooding, and shall not have an adverse effect on the stability of a coastal bank. • The project is a CES as per section4.05, (3). (a). It improves the storm buffer function of the C. Bank. Established sediment mitigation provides for sediment donations. 4.10 Land Subject to Coastal Storm Flow Most if not all CES projects are within coastal flood zones. Such projects are not buildings nor necessarily obstructive features but instead are designed to minimize flood related impacts. The subject case has no nearby structure caused to be at collateral risk from flood forces unlike within a residential area within a flood zone. The review of a CES under this section can set reasonably aside the broader context of the regulations for more significant concerns in flood zones where relevant concern for floating debris and diverted flood waters pose threats to adjacent buildings a property. Any activity within land subject to coastal storm flowage which will result in the building upon, removing, filling, or altering of land shall not have an adverse effect on the interests protected by the bylaw by: i. reducing the ability of the land to absorb and contain flood waters; • The project improves the ability of the land to absorb and contain flood waters. 11 ii. reducing the ability of the land to buffer more inland areas from flooding and wave damage • The project enhances this ability as stated because it contributes to bank stability. iii. increasing the elevation or velocity of flood waters, or by redirecting or increasing flows or causing channelization. • The isolated beach cell will respond as it has for the past 80 years since the surrounding stone groin features were built. The sharp, vertical land slope that develops during severe coastal storms causes for significant wave reflection. The textured, sloped stone revetment face. iv. in each case at the project site, adjacent or nearby properties, or any public or private way. v. The existing features are part of a collection of long existing stone breakwaters and groins, 10 ft. below the velocity flood elevation. The features have been responding to the flood forces delivered to the area for half a century. The repairs will not cause for a significant change to the localized storm action behavior. vi. displacing or diverting flood waters to other properties or resource areas. Fences and privacy walls, including walls separating one property from another, may obstruct or divert flood flow and waves toward buildings and protected areas. Solid fences (stoc kade and similar) must be constructed with 6 inches of clearance below to allow the passage of floodwaters and wildlife; • The proposed CES is oriented parallel to the shore and will to some extent absorb and divert flood driven waves. The action will be very similar to the diverting action already anticipated by the large boulders and the steep, sharp bank scarp. The textured stone face will absorb some of the energy. No amount of turbulence will affect any structure. vii. causing, or creating the likelihood of, damage to other structures on land within the flood plain as debris (collateral damage); • No portion of the existing terrain can become waterborne. viii. causing ground, surface or saltate pollution triggered by coastal storm flowage; • No component existing or proposed has hazardous material associated. ix. reducing the ability of the resource to serve as a wildlife habitat and migration corridor through activities such as, but not limited to the removal of substantial vegetative cover and/or installation of fencing and other structures which prevent wildlife migration across property. • No significant change is being proposed to the land except where routine doses of sand are placed a stone revetment will be installed and then sand covered. NHESP will have input. x. prevention of the migration of resource areas such as salt marshes due to sea level rise. • Salt marsh is not applicable. xi. If flood control and storm damage protection functions have already been impaired, redevelopment must improve existing conditions by reducing impervious surfaces, restoring flood control and storm damage protection functions, installing native plantings, o r by restoring or creating other wetland resource areas. Where a previously developed coastal Resource Area has not been regulated under the applicable performance standards to protect the interests of flood control and storm damage prevention, the proposed work shall restore those interests. This section may not be applicable. And shall meet the following requirements; xii. Existing septic system and cesspool repairs will be allowed provided they meet all Title 5 and local Board of Health thresholds. • Not Applicable. 12 xiii. All groundwater elevations shall incorporate seasonable adjustments if test holes and or leaching components are 100 feet or closer from major estuaries. • Not Applicable. xiv. Any proposed deck, shed, or other similar structure must be securely anchored to a footing or foundation. • Not Applicable. xv. Any activity shall preserve existing soils, vegetation, and other natural conditions that serve as buffers to coastal flooding and storm surges. The proposed activity intends to preserve the upland to a better extent than at present. Preserving the upland offers a significant benefit toward the interest of storm damage prevention and flood control. With appropriate mitigation this effort meets the standard. (b) Additional Performance Standards within the V Zone Within the V Zone, in addition to the general performance standards set forth in Section 4.10, (3)(a), the following additional performance standards shall apply: i. No new construction or footprint expansion of any building or other structure, road, impervious surface, or septic system shall be permitted. • Not Applicable ii. No new construction or expansion of any structure that redirects or channelizes floods including retaining walls, fences, and sea walls shall be permitted. The revetment, as stated previously does not in a significant way divert or channelize flood waters. The revetment is intended to absorb waves to some extent and prevent said waves from routinely undercutting the Coastal Bank. With the revetment cap elevation approx.. 4 ft. below the 100 year flood elevation the velocity Zone flood waters as mapped by FEMA will be significantly over and landward of the stone revetment. iii. With respect to any building or other structure, in the event of any substantial repair of the foundation, any substantial improvement (as defined in the state building code), the entire building or structure shall be elevated at least two (2) feet above the BFE. • Not Applicable iv. The use of fill is prohibited except for bank, dune, or beach nourishment/restoration. • The only fill proposed is for beach nourishment/restoration. IMPACTS CONSTRUCTED ALTERNATIVE WAVE REFLECTION LONGEVITY DURABILITY MATERIAL COMPATIBILITY WITH LOCAL ENVIRONMENT COASTAL BANK SURFACE AREA OCCUPATION COASTAL BEACH AREA OCCUPATION PRACTICAL EFFECTIVE LEVEL OF PROTECTION MAINTENANCE REPAIR / REPLACE COLLATERAL EFFECTS VERTICAL BULKHEAD REPLACEMENT HIGH DECADES BUT WITH SCOUR RISK REMNANT DEBRIS MODERATE WITH WEATHERING & CORROSION POOR : PLASTIC / STEEL / TREATED WOOD PARTIAL 25% - 35% WALL HEIGHT W/ BACKFILL COVERS THE LOWER SLOPE MINIMAL MODERATE TO HIGH WITH APPROPRIATE HEIGHT SHORT TERM: MINIMAL; LONG TERM DEBRIS COLLECTION; SED. REPLENISHMENT TRANSLATED SCOUR FROM HYDRAULIC REFLECTIVITY STONE REVETMENT CAP ELEV. = 11 (PROPOSAL) MODERATE TO LOW DECADES MATERIAL CAN BE RESET / RENOVATED HIGH GOOD : NATIVE STONE PARTIAL VARIABLE NATURAL UPPER SLOPE MINIMAL - REVETMENT TOE IS INTENDED AS LANDWARD AS PRACTICAL WELL BELOW BEACH SURFACE MODERATE TO HIGH SHORT TERM: MINIMAL; LONG TERM: POSSIBLE REPAIRS; SED. REPLENISHMENT LOCALIZED SCOUR FROM LOCALIZED TURBULANCE FROM STONES STONE REVETMENT CAP ELEV. 15 TO MATCH VE ZONE ELEV. MODERATE TO LOW DECADES MATERIAL CAN BE RESET HIGH GOOD: NATIVE STONE COMPLETE APPROX. 100 % ALONG SEGMNENT MINIMAL TOE IS LANDWARD OF THE MANMADE WALL HIGH SHORT TERM: MINIMAL; LONG TERM :MINIMAL; SED. REPLENISHMENT LOCALIZED SCOUR FROM LOCALIZED TURBULANCE FROM STONES COIR SAND LIFT MODERATE HIGHER WHEN UNCOVERED 4 TO 6 YEARS WEATHER DEPENDENT MINIMAL DEBRIS LOW MODERATE : NON-NATIVE DEGRADABLE FIBERS PARTIAL APPROX. 25% TO 50% LOWER SLOPE MINIMAL MODERATE AT OUTSET LOW IN THE LONGTERM SHORT TERM: ROUTINE COVER SAND DELIVERY AND PLACEMENT LONG TERM: REPLACE LIFT TRANSLATED SCOUR FROM SMOOTH LIFT BODY; ONGOING WORK ACTVITY APPENDIX "A"911, 921 GREAT ISLAND ROAD - REVETMENT PROJECT NARRATIVE APEND.A. SHT 1 IMPACTS COIR ROLLS LOW HIGHER WHEN UNCOVERED 2 TO 5 YEARS WEATHER DEPENDENT SCATTERS IN STORMS LOW MODERATE: NON- NATIVE DEGRADABLE FIBER; GALVANIZED / STAINLESS HARDWARE PARTIAL APPROX. 25% LOWER SLOPE MINIMAL LOW SHORT TERM: ROUTINE COVER SAND PLACEMENT; LONG TERM: REPLACE ROLLS AND ANCHORS TRANSLATED / LOCALIZED SCOUR; ONGOING WORK ACTVITY STONE REVETMENT – EL. < 11 MODERATE TO LOW MODERATE DUE TO OVER- TOPPING DAMAGE MODERATE HIGH DAMAGE RISK WITH LOW ELEV. GOOD: NATIVE STONE PARTIAL 20% - 30% LOWER SLOPE MINIMAL MODERATE RISK OF OVER TOPPING EROSION HIGHER RISK W/ LOWER ELEV. SHORT TERM: MODERATE. REPAIR STORM DAMAGE LONG TERM: HIGH; SAND REPLENISH. LOCALIZED SCOUR ABOVE AND ADJACENTT TURBULANCE FROM STONES GABION MODERATE DEPENDENT ON STONE TEXTURE AND GABION STACK SLOPE 1 TO 2 DECADES DEPENDENT ON WIRE CAGE CORROSION; FUTURE DEBRIS MODERATE POOR: VARIABLE NATIVE / MINED SOURCE STONE; VINYL STEEL WIRE PARTIAL 25 % TO 40% CAP HEIGHT DEPENDENT; LOWER SLOPE MINIMAL MODERATE HEIGHT RESTRICTED SHORT TERM: SEDIMENT REPLENISHMENT; LONG TERM: SED. REPLENISH. DEBRIS CLEANUP: CAGES AND STONE CHIPS LOCALIZED SCOUR LIVING SHORELINE LOW 1 TO 2 YEARS – STORM- DEPENDENT LOW GOOD: SELECTED NATIVE MATERIALS MINIMAL; INTENT IS TO MIMIC THE LAND FORM MINIMAL; INYENT IS TO MIMIC THE LANDFORM VERY POOR HIGH EXPOSURE; VULNERABLE GROWING CONDITIONS SHORT TERM: MONITORING AND REPLACEMENT; LONG TERM: REPLACEMENT CONTINUAL WORK ACTVITY ZONE TO REPAIR / REPLACE STATUS QUO SAND NOURISHMENT ALONG C. BANK SCARP LOW SHORT TERM STORM DEPENDENT LOW CONTINUAL DISTRIBUTION CONSISTENT PARTIAL TO COMPLETE DEPENDING ON VOLUME MODERATE DUE TO SAND SLOPE; SAND – TO SAND LOW TO POOR DUE TO EXPOSURE SHORT TERM ROUTINE REPLACEMENT POSITIVE FOR BEACH DEPOSIT. APEND. A SHT 2 APPENDIX B TO PROJECT NARRATIVE Construction Guidelines and Work Protocol 911 Great Island Rd. West Yarmouth Construction of a Stone Revetment The following is a guideline to describe the method of construction, material handling, access, equipment type, equipment storage, and schedule related to the proposed delivery of materials and construction of the stone revetment to replace cabled coir fiber roll erosion protection measures. This description is the result of an onsite review of the site conditions, and of the common construction practices with a local experienced construction contractor. Term of Construction The proposed work should take approximately 4 weeks to complete. The schedule is affected slightly by tides. Very high tides or storms can restrict the work area on the beach and shall be considered to have minor effects effect on schedule. Anticipated work activity time is during November thru April, weather permitting, with stone work completion allowing ample time prior to the spring season to plant the upper bank zone prior to the onset of the growing season. NHESP time of year restriction will likely have an April 1 cut-off. Stockpiles and Staging Limited material stockpile and equipment staging shall be within the open, sand beach area and the existing access way. Remaining coir and related anchor debris encountered shall be controlled and removed from the property as it is generated. Stone revetment material quantity must be limited to several day’s supply. Armor stone is secure from being lost. Bedding stone shall be confined in a 15-yard steel bin. Geotextile shall be in tightly bound rolls stored in the upland. Work Access Route The route for hand labor access is via the existing driveway route to the property and the path to the beach. The machine and material route is a narrow over-land travelled way routinely used for beach sediment delivery. The existing route to the work site was used for the past 17-year coir log maintenance and sand nourishment process. It is durable, glacially originated upland ground with demonstrated capability of supporting truckloads of a similar type and weight as will be generated by the proposed activity. The route shall be over seeded with native grass when the delivery is completed. The route is intended to remain as it has been, available for the ongoing sand mitigation delivery activity. Equipment Equipment utilized is listed as follows: • A steel track excavator • Rubber – tire front end loader • Delivery trucks – 10-wheel dump body • In conformance with encouraged practice the trucks and machines shall not be allowed to idle unless they are engaged in a direct work effort. • A spill kit managed by the revetment contractor shall be on site and readily accessible during the work term. Construction Procedure First, the site shall be prepared for access with sand fill at the access point. Segments of the proposed revetment will be handled in manageable lengths of approx. 50 ft. The proposed revetment is intended to be set in place as far landward as physically practical. The work shall proceed from south to north to the access point. A short length shall be installed from north to south to the access point. The segment utilized for access shall be completed last as the equipment leaves the beach area. The access location remains as a practical sediment delivery point, fortified by the revetment, allowing for sediment deliveries without risk to the C. Bank stability. Segments of the stone revetment will be developed as follows: • Debris from the remnant coir array when encountered shall be taken away for disposal. • The bank shall be contoured in the lower zone where the revetment will go. Scarped areas shall be re- contoured. Root material shall be preserved as much as practical. Upper bank vegetated slopes shall be preserved. • Board templates shall be erected to assist with shape, elevation, alignment and fit and shall be maintained during the job. • Beginning on the south end the effort will begin to set the fabric, toes stones, face materials and bedding stone. Progress rate will be determined after a day or two of initial work with an estimate of 4 to 5 weeks to completion. • During each day the work crew keeps track of all unnecessary materials or encountered coir roll debris and those items are removed as they are generated and transported away. • Each 50 ft. revetment segment activity repeats the previous segment activity until the access point is reached. • Clean compatible sand in an amount approximating 110 c.y. shall be delivered into the revetment face interstices for a successive tidal introduction to the near shore zone. This is separate from the annual mitigation sediment. • The access location, approx. 15 ft. width shall be managed with sand replenishment activity and planted. This location is expected to be used for routine sediment replenishment and planted with beach grass periodically. • All material, the excavator, loader, and other tools, etc. are removed, the site cleared of any remaining stone pieces with exception of the natural stone content. • Access route is examined, raked out and overseeded with native grass seed. • Vegetation planting activity (Am. beach grass) outlined below, follows within any altered area along the revetment cap where needed as soon as weather permits. Upper slope planting will include native shrubs where available space and observed need permits. The existing growth along the bank top shall be preserved and is expected to prosper. The revetment work is highly repetitive. A pattern will be established and maintained. Routine job site inspection including elevation confirmation, general construction quality, work practice, material handling shall be a requirement during the work term. Clean Up and Upper Bank Restoration • Any exposed slope areas along the top of revetment shall be heavily planted with grasses, Am. Beach grass ( 2 culms) @ 12 in. O.C. spacing at a suitable time of year. The anticipated schedule is intended to have beach grass installed as the job proceeds but with a complete planting effort immediately following completion of stone work. Native shrubs of a 3 gal. size, bayberry, beach plum will be installed in upper slope areas lacking cover where space permits based on a post job inspection. Native upland seed mix shall be distributed across the slope for added diversity. • The access points shall be inspected. Follow-up inspection follows for a non-specific term to monitor the area.