08/21/2025 CONSERVATION COMMISSION Minutes

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Town of Mashpee Conservation Commission 16 Great Neck Road North Mashpee, MA 02649 be removed, and new stone would be installed, though any existing pieces of adequate size might be reused if deemed suitable by the contractor. 22 Triton Way- Engineering Details and Long-Term Stability Discussion Mr. Dibb continued to explain the construction sequence, noting that the work would begin with placement of five- to eight-ton "armor stones" set over a foundation layer of smaller one-ton stones. The intent, he said, was not to create a smooth, uniform slope but rather to introduce roughness and varied angles to absorb wave energy more effectively. In response to a commissioner's question, he clarified that armor stones are large, irregularly shaped rocks designed to resist wave impact and prevent erosion along the slope. Commissioners expressed curiosity about the engineering of the existing concrete wall, particularly how it has prevented water infiltration and erosion behind it over time. Mr. Dibb acknowledged uncertainty about the exact design but believed the return section of the concrete wall likely extended back into the bank at full height, offering additional stability. He pointed out that stones placed along the bottom of the structure were still properly sloped, suggesting that while the wall remained relatively stable for now, further deterioration would occur if left unrepaired. A commissioner emphasized that while the short-term safety concern was clear, the Commission also needed assurance that the long-term stabilization plan would not cause future destabilization or increase storm- related impacts. Mr. Dibb confirmed that the plan involved removing all existing boulders and rebuilding the revetment according to the new engineered profile. Larger"tow stones"would be installed at the base, properly aligned with the concrete wall, with materials transported and placed by barge. The resulting structure, he explained, would match the slope and stability of the newer neighboring revetments and comply with recommendations to remove and reconstruct the existing failed stonework. Mr. McManus expressed some concern about the higher proposed profile relative to adjacent revetments. He cautioned that a steeper, slightly forward section might be more vulnerable to storm surges and could create uneven wave deflection between properties. Mr. Dibb acknowledged the difference but maintained that the proposed design, if constructed as engineered, would be adequately stable and necessary to protect the end of the concrete structure. Commissioners discussed whether the proposed profile would result in two different slope angles between properties and how that might influence long-term erosion. Mr. Dibb admitted there would be a slight difference but emphasized that the stones' weight, slope, and rough finish would prevent significant scouring. Several commissioners agreed that while there was potential for minor variation, the immediate safety risk from the loose, teetering boulders outweighed those concerns. One commissioner added that the unstable condition posed a hazard to anyone walking on the rocks and that action needed to be taken promptly. 22 Triton Way- Consideration of CZM Review and Motion to Close Despite consensus on the need for safety repairs, a commissioner suggested that the project might still benefit from a Coastal Zone Management (CZM) or Barnstable County Extension technical review to evaluate potential long-term impacts and stabilization effectiveness. Mr. McManus agreed this could be done efficiently if the Commission provided CZM with both the current and existing revetment plans for comparison, along with a clear directive rather than two alternative design options. After discussion, the Commission agreed that the proposed plan and the existing neighboring profile could be forwarded to CZM for input. Any resulting recommendations could then be incorporated as conditions without reopening a full hearing, streamlining the process while ensuring technical oversight. Commissioners emphasized that a formal continuance was not necessary, given the urgency of the repair and the clear safety hazards on-site. 23