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Select Board hears modeling showing summer PFOA exposures; debate over notice and short‑term mitigation
Summary
Consultants presented hydraulic modeling showing that summertime operations of the Lakeshore well can deliver PFOA above 4 parts per trillion to a portion of the high‑pressure zone; the board debated notifying affected households, short‑term mitigation (fill station, operation changes), and longer‑term treatment to meet the EPA standard.
Town consultants and the water department presented modeling and monitoring data on July 6 showing that the Lakeshore well’s mean PFOA concentrations have exceeded 4 parts per trillion and that, under summertime demand, modeled finished water at dozens to a few hundred locations in the high‑pressure zone could exceed the EPA’s 4 ppt practical quantitation level.
Austin Potts, project manager for the town’s consultant team, said their hydraulic model used the best available monitoring and operational data to estimate how Lakeshore water mixes in the distribution system. He warned that results are sensitive to operational assumptions and the time of day: "The water system is a very transient operating thing," he said, noting flow patterns change hour‑to‑hour and seasonally.
Water Superintendent Mark Cloud told the board Lakeshore samples have ranged from about 2.5 up to 7 ppt with an average near 4.5 ppt since monitoring began; consultants and town staff disagreed over whether multi‑year averages (used for regulatory compliance modeling) or current values should drive immediate public notification and response.
Board members pushed for practical mitigations: short‑term options included adjusting well start/stop logic so lower‑PFOA wells supply the tank first, establishing a public filtered‑water fill station (as other towns have done while treatment is built), targeted finished‑water testing at nodes the model identifies as likely above 4 ppt, and stepped public outreach to affected customers. Austin Potts and staff emphasized tradeoffs: changing well controls can increase drawdown on other groundwater sources and cause operational issues (well performance, water age), and installing temporary filtration points has material cost and logistics implications.
Staff said they are pursuing a longer‑term treatment strategy (design work is already underway for one treatment facility) aimed at compliance by the EPA timetable; the board asked staff to prepare a public notification plan, targeted finished‑water testing in areas the model flags, and a short‑term fill or filtered‑water station option while treatment is designed and built.
Select Board members also discussed demand reduction and enforcement of outdoor irrigation bans as a tool to lower summertime demand and reduce reliance on the Lakeshore well.
The board requested staff return with a clear public‑notification draft (reviewed by town counsel and the Board of Health), an operational scenario analysis that shows the modeled PFOA effect of control‑logic changes, and a cost estimate and timeline for a temporary filtered‑fill station.
