11/13/2025 CONSERVATION COMMISSION Minutes (2)

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Town of Mashpee Conservation Commission 16 Great Neck Road North Mashpee, MA 02649 Regarding flood design,Attorney Brodsky explained that: • The skirting around the elevated structure is designed with sufficient open area to meet both Massachusetts Building Code and International Residential Code requirements for flood vents in this flood zone. • In addition, the team proposes Smart Vent-type mechanical flood vents within the skirting to provide redundant, automatic flood openings and further ensure that water can flow freely in and out under the structure, reducing hydrostatic pressure during flood events. He then turned the presentation over to Mr. Garelli and Ms. Labovitch for design details. Retaining Wall Design,Drainage, and Wildlife Corridor Mr. Garelli, landscape architect, described the proposed retaining wall system in more detail. The wall will be a modular block system as follows: • Shallow excavation with compacted gravel beneath and behind the wall for stability. • A drainpipe at the base of the wall tied into the dry well, to collect and direct subsurface water. • Filter fabric near the top of the gravel backfill to separate loam from the drainage stone and prevent fine soil from washing into and clogging the drainage layer. • Finished soil grade will be kept approximately two inches below the top of the wall coping, so stormwater does not spill over the top of the wall during heavy rain events. He confirmed that the remainder of the landscape plan is unchanged from the prior submittal and that the Commission had been generally satisfied with that approach. He highlighted the presence of a"wildlife corridor" around three sides of the property: between the abutters' retaining wall and the applicants' wall, bayberry plantings will be installed, creating a vegetated and permeable corridor that allows wildlife movement and softens the visual impact of the hard structures. Skirting, Flood Opening Sizing, and Smart Vents Ms. Labovitch then reviewed the skirting and flood-opening calculations for the new structure: • The enclosed area beneath the building is approximately 1,936 sq. ft. • The skirting openings alone provide about 2,016 square units of opening, meeting and slightly exceeding the required ratio of opening area to enclosed area. • An additional five mechanical flood vents are proposed, which effectively double the available flood- opening capacity and provide redundancy under a range of flood conditions. She confirmed that the design, as revised, is intended to fully satisfy code requirements and Commission expectations for floodplain design. Chair Cook thanked her for clarifying the flood vent strategy. Commissioner Questions Slab vs. Gravel and Sub-Foundation Permeability Mr. Colombo asked about the material beneath the elevated structure. He recalled prior discussion about "cutouts" in a slab and asked whether the project still proposed a concrete slab under the house. The project team responded that: • The owners are willing to forego a concrete slab under the structure in favor of gravel if that is the Commission's preference. • Using gravel instead of concrete will improve infiltration and percolation under the building and avoid creating an impervious surface in the floodplain. Mr. Colombo stated that gravel was his preferred option and thanked the applicants for agreeing to that change. 12