04/23/2026 CONSERVATION COMMISSION Minutes

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Town of Mashpee Conservation Commission 16 Great Neck Road North Mashpee, MA 02649 NOI Ashumet Pond, Commonwealth. Proposed plan implementation of an alum treatment within 50.6 acres over the portion of the pond that is deeper than 10 meters, which is contained within the Ashumet Pond, and the state boat launch off Sandwich Road. (Representative: Ashley Fisher, Town of Mashpee, Water Quality Coordinator). 43- 3411 The Commission reviewed the proposed alum treatment for Ashumet,presented by Mr. Ed Eichner of TMDL Solutions on behalf of the Town of Mashpee. Mr. Eichner explained that the project involved treatment of approximately 50.6 acres of the pond in areas deeper than 10 meters to address internal phosphorus loading and associated cyanobacteria blooms. He stated that alum binds phosphorus in the sediments, preventing its release into the water column, and noted that prior treatments had been conducted in 2001 and 2010. The proposal included pre-, during-, and post-treatment monitoring, with post-treatment monitoring continuing for three years, and measures to avoid impacts to mapped freshwater mussel habitat and maintain acceptable pH levels. Commission members asked questions regarding the monitoring plan, coordination with the Town of Falmouth, treatment duration, and long-term water quality management. Mr. Eichner stated that the treatment would take approximately one to three days under optimal conditions and would provide temporary improvement, while long-term solutions would require watershed-level interventions, including sewering and nutrient management. The Commission read into the record letters of strong support from Susan Dengel, Chair of the Mashpee Freshwater Ponds Committee and representative of the Save Mashpee-Wakeby Pond Alliance, both letters expressing strong support for the alum treatment as a scientifically supported method to reduce phosphorus and improve water quality, and urging timely approval. A third letter from Ken Oroski, representing the Friends of Ashumet Pond, also expressed support and emphasized the urgency of addressing declining pond conditions and recurring algal blooms. PUBLIC COMMENT ON ASHUMET POND Ken Oroski reiterated support for the project, noting long-term phosphorus loading in the pond and the effectiveness of prior alum treatment, while emphasizing the need for a long-term solution. John Greiner expressed concerns regarding ecological impacts, citing observations of reduced fish and wildlife populations following prior alum treatment. Hope Karajanis asked questions regarding the duration of treatment, safety for recreational use, and impacts to fish and wildlife. In response, Mr. Eichner stated that the treatment would occur in deeper portions of the pond that are largely devoid of oxygen and aquatic life during summer months, and that the alum would settle out of the water column within approximately one day. He explained that modern alum treatments use a buffered combination of aluminum compounds to maintain stable pH levels and avoid fish kills, noting that earlier issues informed current best practices. He further stated that while the treatment may reduce overall biological productivity, it would improve overall pond health by reducing harmful cyanobacteria blooms. II