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HomeMy WebLinkAboutPerformance Standards updatePerformance Standards Narrative, Alternatives Analysis, and Construction Protocol - updated Property Description The property is located on Bass River, a tidal river that leads to Nantucket sound. The project site is approximately 1.5 miles inland from Nantucket Sound. The property is located on the western shore of the river, adjacent to a town marina. The property has an existing single family dwelling. The assessors records indicate that the dwelling was built in 1935. All of the existing structures (seawall, dock, piles, steps, etc. have an existing Chapter 91 License (DEP Interim Approval No. 2973, issued in 1992). This license has a 30-year term. There is an existing rock and concrete retaining wall with steps to the water. In 2018, a new vinyl bulkhead was placed landward of the existing stone wall per SE83-2109. The area landward of the existing concrete wall consists of a unimproved “cape cod” lawn. The property is mostly in Land Subject To Coastal Storm Flowage, with the Top of Coastal Bank at the edge of the second concrete wall, about 80 feet landward. The lower lawn area floods frequently. There are pictures attached to this filing that show various flooding events in 2012, 2014, and 2020. In all cases, the lower lawn get completely inundated. The adjacent property to the south (Austin) has a slightly higher lawn area that is much more resistant to flooding. Project Description The purpose of this project is to fill the lower lawn area to raise the grade to match the adjacent property to the south. Loamy fill will be brought in and graded to match the existing adjacent grades. 8”x8” timbers will be placed at the landward edge of the existing gravel buffer strip to contain the fill and preserve the gravel buffer. Approximately 161 cubic yards of fill will be needed and placed over the existing lawn area. The fill will be graded to match the adjacent properties on both sides. In this way the Perrone property will not be directing flood waters onto adjacent properties; merely matching them so they all flood at the same time. There is a gap between the applicant’s wall and the town bulkhead to the north, which currently allows flood waters to drain as they recede. This gap will not be changed to allow for future drainage. The newly graded area will be seeded with a salt tolerant “Cape Cod” seed mix. Temporary irrigation may be used to get the grass established. As long as something can grow in that area, it will hold the soil and prevent siltation. The area will be seeded and allowed to naturalize. No permanent irrigation or fertilizer is proposed. Alternatives Analysis (Discussion of Options) Option 1- Do nothing If nothing is done at this site, the property will continue to flood, likely with more severe and frequent events. Eventually, the lawn will no longer be able to sustain itself. The area is not flooded during normal tides, so planting any marsh is not possible. Vegetation keeps the soil more porous, increasing infiltration, and removes excess water through evaporation and transpiration. If the area becomes void of vegetation, then future storm events could start removing soil and transporting it by wave action into the river. This would be a very undesirable result. Therefore, doing nothing doesn’t preserve the area, and leaves it open for siltation. Therefore, this is not the desired option. Option 2 – Raise the bulkhead to match the south bulkhead. This option was discussed during the design phase of the project. It was not chosen because of the additional cost of the viny sheeting. Further, the town bulkhead to the north has a gap that allows flood water to enter the property without overtopping the applicant’s bulkhead; the water would just come from around the back side and flood the property anyway. So raising the bulkhead alone does not solve the problem. Therefore, this option does not really solve the problem long term, and is therefore not the desired option. Option 3 – Seal the Perrone bulkhead to the town bulkhead. This option requires doing work on town property. In addition, sealing the two walls will create a “bath tub” of water behind the bulkhead. During flooding, when the water overtops the bulkhead (see attached photos), the water will flood the site, but then has no way to leave when flood waters reside. So again, this doesn’t solve the problem and actually makes it worse, because the water can’t drain as the flood waters recede. Therefore, this was not a chosen option. Option 6 - (preferred alternative, project as proposed). This option provides the intended outcome, and solves the flooding problem to a point that equals the properties on both sides. It is also an economical solution for the applicant. Therefore, it is the preferred option. Performance Standards The project proposes the filling of an area to raise the elevation to reduce flooding events. It will not prevent them, but it will reduce the frequency of the more common storm surge events. The entire area, as well as the adjacent properties, is well below the flood elevation and will flood completely in larger storm events. Land Subject to Coastal Storm Flowage (LSCSF) – LSCSF is considered a resource area under 310 CMR 10, section 10.02 (1) d. The area from the second (more landward) rock wall to the waterfront is below the flood elevation and therefore no coastal bank exists. There is an “artificial Top of Bank” at the top of the landward rock wall, but the work area is not in this area. The work on the waterfront is still within LSCSF, so it will be treated as such. The area is therefore within Land Subject to Coastal Storm Flowage. Although LSCSF is an area that is allowed protection under the Wetlands Protection Act, there are no performance standards for this area. The work proposed in LSCSF is the work for the fill and landscaping. That work will not have any significant adverse impacts, and can be permitted under 310 CMR 10.05(6)k. Riverfront Area - There is both 100-foot and 200-foot riverfront area buffer zones on this property. The work in the 0-100 riverfront area is limited to the fill which amounts to approximately 161 cubic yards of material placed over approximately 8,400 square feet. None of this work will negatively impact the riverfront area itself. Flooding will be less, and drainage will be improved. Full restoration of the “Cape Cod” lawn will keep the area stable and vegetated, at least to the point of having no exposed soil to be introduced into the waterway. Please refer to the discussion of project alternative stated previously in this narrative. Riverfront Performance Standards 310 CMR 10.58 (3); “Where a proposed activity involves work within the riverfront area, the issuing authority shall presume that the area is significant to protect the private or public water supply; to protect the groundwater; to provide flood control; to prevent storm damage; to prevent pollution; to protect land containing shellfish; to protect wildlife habitat; and to protect fisheries.” The riverfront area on this property provides recharge and retainage of flood waters, which mitigates flooding and damage from storms. The root systems of the vegetation keep the soil porous, increasing infiltration capacity. Vegetation also removes excess water through evaporation and transpiration. Vegetated riverfronts also dissipate the energy of storm flows, reducing damage to pubic and private property. There is no vegetative cover for fisheries for this site, so this function does not appear to be applicable for this property. The riverfront area, being so close to a salt water river, likely does not provide protection for private or public water supplies or groundwater. In these areas, there is likely an amount of salt water intrusion into the groundwater at some distance from the river’s edge, and at lower elevations. The other functions of the riverfront area, such as flood control, storm damage prevention, and the prevention of pollution, the protection of land containing shellfish (there is a coastal beach here, but it’s covered mostly by rocks, where shellfish might be present), wildlife habitat. Therefore, it appears that three of the interests may not be applicable for this property. “By providing recharge and retaining natural flood storage, as well as by slowing surface water runoff, riverfront areas can mitigate flooding and damage from storms. The root systems of riverfront vegetation keep soil porous, increasing infiltration capacity. Vegetation also removes excess water through evaporation and transpiration. This removal of water from the soil allows for more infiltration when flooding occurs. Increases in storage of floodwaters can decrease peak discharges and reduce storm damage. Vegetated riverfronts also dissipate the energy of storm flows, reducing damage to public and private property.” This is the primary function of the riverfront area for this property. “Where the presumption set forth in 310 CMR 10.58(3) is not overcome, the applicant shall prove by a preponderance of the evidence that there are no practicable and substantially equivalent economic alternatives to the proposed project with less adverse effects on the interests identified in M.G.L. c.131 § 40 and that the work, including proposed mitigation, will have no significant adverse impact on the riverfront area to protect the interests identified in M.G.L. c. 131 § 40.” According to the above, the riverfront area may not play a role in in the protection of fisheries, groundwater or private or public water supplies. This equates to the “one or more” of the interests in 310CMR 10.58(3). Therefore it appears that the presumption is rebuttable, and the presumption of significance is partially overcome. However, there are no practicable and substantially equivalent economic alternatives (see alternatives, above) to the proposed project with less adverse effects. Even the “do nothing” option has adverse effects to the riverfront area interests. The proposed work will have no significant adverse impact on the riverfront area to protect the interests identified in M.G.L. c. 131 § 40. CONSTRUCTION PROTOCOL The staging area for equipment (likely just a dump truck and skid steer) on the applicant’s property on the lower level. The work area is the entire lower lawn area. Access will be from the street immediately north and adjacent to the site, as was the case when the bulkhead was built. No equipment will be stored in that street or the parking lot. All equipment shall be stored on the applicant’s property when not in use. Pre-Construction Meeting If required, and Prior to construction, a pre-construction meeting shall be held on-site with the Contractor, Property Owner (or owner’s representative), and the Conservation agent. The purpose of the meeting is to clearly delineate the limits of work and access, as well as the staging area. The Contractor will describe the proposed means and methods for performing the work within the requirements of the plans, order of conditions and construction protocol. The Contractor will comply with mitigation measures as established by the Conservation Commission. To be discussed at this meeting: Existing property conditions, necessary precautions to be taken by the Contractor; Means and methods for construction; Means and methods for siltation controls; Necessary post-construction reparations and conditions; Procedure for post-construction inspection; Shorefront Consulting’s responsibilities for inspection and project coordination During Construction, the site shall be accessible for inspection during reasonable hours by all parties, members of the conservation commission and their agents, and the Project Manger. Post-construction meeting Upon completion of construction, a post-construction meeting shall be held on-site with the Contractor, Property Owner (or owner’s representative), and the Conservation agent. The purpose of this meeting is to determine that the project has been satisfactorily completed in accordance with all permits, and that no additional work or mitigation is required by the Contractor. Restoration of project area Upon completion of construction, the staging areas, vegetated areas, and any other areas disturbed by the construction effort shall be returned as much as practical to their pre-construction conditions to the satisfaction of the property owner and conservation agent.