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City reports trace pesticide detections in monitoring wells; officials say Keene drinking water remains safe
Summary
City lab detected low‑level pesticide traces (including the fungicide iprodione) in monitoring wells near Court Street; concentrations in production wells were well below EPA health benchmarks, the affected well has been taken offline, and the city is expanding sampling with state pesticide regulators.
Keene water‑system staff told the Municipal Services, Facilities & Infrastructure Committee that trace detections of several pesticides have appeared in monitoring wells near the Court Street groundwater supply, but that testing shows drinking water remains safe.
"The city's water supply is safe," Assistant Public Works Director Aaron Costa told committee members, adding that the city was being intentionally transparent even though detected levels were far below any federal health benchmarks. Lab manager Andrew Kaiser described detections in monitoring wells that began to appear in 2019 as laboratory detection limits improved; in October 2025 staff found low levels of iprodione in production well 3 but at concentrations many times lower than chronic health benchmarks cited by EPA.
Kaiser said the city immediately removed the affected production well from service, retested and purged it, and will not return it to service until repeated testing shows results the operations team is confident in. "We typically don't use that well anyway… we still have not used it," he said. State regulators (DEES and the Bureau of Pesticide Control) reviewed the data and indicated no public notification was required because concentrations are below human‑health benchmarks, but the state is developing a pesticide management area and a management plan for the Court Street wells.
To improve monitoring and reduce multi‑year gaps in data, city staff outlined an expanded schedule of sampling (spring, summer and fall rounds) covering 17 locations including all four production wells, nine monitoring wells, reservoir raw water, and river samples upstream and downstream of nearby applicators. Kaiser cautioned that advanced pesticide analyses are expensive (sample costs of roughly $1,375–$1,700 each) and that some compounds used locally do not have widely available low‑detection laboratory methods.
The committee approved a motion to accept the staff report as informational. City staff said the budget includes a $75,000 supplemental to support expanded testing this year and that interns and additional operations staff will help conduct the sampling program.
The city plans to continue coordinating with state pesticide regulators and to share monitoring results publicly as they are available.
