07/17/2025 SEWER COMMISSION Minutes (2)

Home Browse Search

Town of Mashpee Sewer Commission t 16 Great Neck Road North Mashpee, MA 02649 Update on Alum Treatment Project(Presented by Ashley Fisher) Ms. Fisher provided a comprehensive update on the proposed alum (aluminum sulfate)treatment for Mashpee-Wakeby Pond, which is designed to combat internal phosphorus loading in conjunction with the cluster system addressing external loading. Key elements of the update: • The town has allocated $250,000 for the initial phase of the project, which covers: o Nutrient inactivation planning o Permitting o Data collection • A Request for Proposals (RFP) will be released on August 11, 2025, The RFP includes: • Sediment core sampling, including more comprehensive sampling than was done in the prior diagnostic assessment • Permitting work through multiple regulatory bodies: o Massachusetts Department of Environmental Protection (DEP) o Natural Heritage & Endangered Species Program (NHESP) • Post-treatment monitoring lasting two years to evaluate long-term impact The RFP contractor will not apply the alum treatment itself but will: • Handle data collection, permitting, and compliance preparation • Coordinate with the future alum applicator contractor for implementation Anticipated Timeline for Alum Application Commissioner Lyons asked for clarification on the project timeline: • Ms. Fisher explained that: o The actual application of alum is likely at least two years away, due to the complexity of the permitting process and environmental constraints. o Permitting will require: ■ Detailed mussel population surveys conducted by divers ■ Consideration of seasonal restrictions, particularly related to herring runs • In a best-case scenario, alum treatment would begin in 2027, if all permitting proceeds smoothly. The alum treatment works by: • Binding phosphorus in pond sediments, preventing it from entering the water column during seasonal mixing • Reducing the frequency and intensity of algae blooms It was compared to "shocking a swimming pool," in that it chemically resets water quality conditions. Potential Lifespan of Treatment • Ms. Fisher noted that the effectiveness of the alum treatment depends on whether external phosphorus sources (mainly homes with septic systems) are eliminated. • If the Mashpee-Wakeby cluster system is completed and those properties are taken "offline," the treatment could be permanent or long-lasting.