Consultant: PFAS contamination around Kingston fire station is delineated; more sampling, a groundwater-management permit and 12 new monitoring wells planned

Bill Maher, senior project manager for Sanborn Head, told the Kingston Board of Health on March 31 that the consulting firm will submit a supplemental site investigation this summer and expects to file a Groundwater Management Permit after additional monitoring wells are installed.

The investigation follows state testing that found elevated per- and polyfluoroalkyl substances (PFAS) in and around the town's former fire station. "We do think there's a suggestion that there are multiple sources, not just the fire station," Maher said, describing chemical signatures and groundwater flow as complicating factors. The state's contaminated-site rules (Env-Or 600) will govern the next steps.

Why this matters: PFAS are persistent "forever" chemicals used in many consumer products and in aqueous film-forming foam (AFFF) used for firefighting. Sanborn Head said 27 household point-of-entry treatment (POET) systems are in place, one property is receiving bottled water, and six private wells are on a sampling schedule. The town, as the responsible party named by New Hampshire Department of Environmental Services (NHDES), must complete investigation, monitoring and controls until groundwater meets state Ambient Groundwater Quality Standards (AGQS).

Sanborn Head summarized the site history and next steps. The firm said Stantec's earlier work showed PFAS in groundwater and in sediment tied to an old floor-drain dry well at the demolished fire station. Subsequent sampling expanded the number of affected properties after NHDES lowered state AGQS values. Maher and Sanborn Head senior vice president Russ Abel said concentrations around the fire station are generally stable or decreasing, which suggests no ongoing large source is being added.

Sanborn Head's near-term plan includes: - A supplemental site investigation this summer to address state data questions about the former dry well, former septic areas at the fire station and PFAS at the Kingston Plains. - Installation of 12 new overburden (shallow) monitoring wells and additional surface-water gauges to clarify groundwater flow directions. - A consolidated report to NHDES supporting a Groundwater Management Permit application, targeted for late Q2 to Q3 2025.

Russ Abel said the permit will formalize monitoring, operation-and-maintenance (O&M) requirements for POET systems and place a Groundwater Management Zone (GMZ) on record. "The groundwater management zone just defines the area on the map where the contamination is," Abel said. Properties placed inside a GMZ normally have a notice recorded at the registry of deeds and restrictions on new wells or required sampling before water use.

Board and audience questions focused on source identification and public notification. Maher said chemical "fingerprinting" and groundwater-flow mapping are both needed to attribute impacts; in practice attribution can be difficult and often relies on multiple lines of evidence. He said bedrock flow is more complex than overburden (sandy) groundwater, and additional wells are intended to reduce that uncertainty.

Sanborn Head said the town's consultant bid package for the supplemental field work is out now; the company expects to collect field data this summer and submit an updated report to the state by August. The firm told the board that NHDES could require additional work if off-site exceedances remain near the GMZ boundary. Maher said the groundwater-management permit will be reissued periodically while groundwater remains above state limits.

Public questions included requests for the consultants' presentation and for clarification about what owner notifications and protective measures would look like. Sanborn Head said it will provide the town a copy of the presentation and that NHDES provides model notification letters and immediate-notification requirements under the revised Env-Or 600 rules (reissued December 2024). The consultants said the state requires immediate notification to property owners and provision of alternate water if a private well exceeds AGQS.

Ending note: Sanborn Head's work will shape the formal GMZ boundaries and the permit that governs monitoring and POET long-term O&M. The firm expects to return with a report and clearer recommendations after the summer field program.