09/04/2025 CONSERVATION COMMISSION Minutes

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7 Town of Mashpee Conservation Commission 16 Great Neck Road North Mashpee, MA 02649 w$XJI:YYF.µ'1 NOI 89 Bluff Avenue, John & Kirsten DeSanto. Proposed raze of existing dwelling and 43- construct and maintain new single family dwelling with I/A septic system upgrade 3355 and mitigation plantings. (Representative: BSS Design Inc.) (coat. 8.7) (legacy Reg 25) • The proposal involves raising the existing dwelling, constructing a new single-family home with an IA septic system, and incorporating mitigation plantings. The project falls under legacy Regulation 25, as it was filed before the revised regulation took effect. • Attorney Adam Brodsky, representing the applicants,presented an overview. He confirmed that the project complies with legacy Regulation 25 and that no waivers are required under that regulation. While legacy Regulation 25 allows conventional concrete foundations with flood vents, the applicants modified their plan at the Commission's request. The new design proposes concrete piers, a standard typically used in FEMA velocity zones, which exceeds requirements for this site located in AE elevation 13 flood zone. • Mr. Brodsky explained that the project dramatically reduces alteration of floodplain land. The current dwelling alters 1,618 square feet, while the proposed pier-supported structure would reduce that alteration to approximately 55.8 square feet, covering only the piers and septic retaining wall. He emphasized that the project both modernizes the property and enhances flood resilience by eliminating the existing basement and garage, thereby minimizing storm damage risk. • The applicants also submitted a waiver request under Regulation 29 concerning buffer zones, although Mr. Brodsky stated that mitigation plantings are not technically required. They chose to include the waiver out of caution and to demonstrate willingness to meet the Commission's expectations. Additionally, the new IA septic system will significantly reduce nitrogen loading, exceeding Title 5 requirements and improving water quality protection. • Mr. Brodsky concluded by noting that the project represents an overall environmental improvement, replacing a non-conforming structure with one that both reduces permanent alteration in the floodplain and provides superior protection against storm damage. • Surveyor Tom Bunker of BSS Design then described the updated foundation plan in greater detail. The new design features twelve-inch square concrete piers extending to elevation 13 and four feet below grade, leaving the entire area beneath the house open to floodwaters. He explained that this adjustment directly responded to the Commission's concerns during earlier hearings about the impacts of a conventional foundation and addressed both flood storage and flow considerations. He also stated that further described the design, noting that aside from a small retaining wall at the rear to support the raised septic system, the project eliminates traditional foundation walls. The wall is necessary to hold the elevated IA system, which sits more than five feet above groundwater, but otherwise the structure is fully open beneath. Mr. Bunker emphasized that the shift to concrete piers directly addressed the Commission's earlier concerns, leaving the structure free-flowing for floodwaters. • Landscape mitigation was also presented. Landscape architect Andrew Verily proposed a series of native plantings, shown as a pink dot pattern on the submitted plan. These would serve as mitigation for disturbance and enhance natural cover on the property. • Ms. Thornbrugh opened questioning by commending the applicants for adopting the pier foundation, describing it as an excellent modification that benefits both the resource area and the applicants by improving resilience to flood conditions. She also thanked Attorney Brodsky for his detailed Page 8