Merrimack Village District sees seasonal PFOA spikes; escrow for Saint‑Gobain treatment exhausted

Don Provencher, chair of the Merrimack Village District water department, told the Legislative Study Commission on Feb. 14 that the district’s routine PFAS sampling shows recurring seasonal spikes in PFOA and an upward trend in wells nearest the former Saint‑Gobain facility.

“PFOA is really the only thing that is in violation of any groundwater standards in New Hampshire,” Provencher said, and he described repeated late‑summer into fall peaks across multiple production wells. He told commissioners that wells 4 and 5 — the two closest to the Saint‑Gobain site — have shown an upward trend since about 2023.

The pattern described by Provencher shows spikes at wells across Merrimack and nearby Hollis, often in late summer and into the fall. Provencher said one hypothesis is reduced groundwater recharge during drier periods can concentrate PFAS in the aquifer; he also noted uncertainty in early laboratory data and that some wells (well 3) were taken out of service because of high sodium and chloride.

Why it matters: recurring and, in some wells, rising PFOA concentrations affect the district’s treatment operations and…