Consultants report major PFAS cleanup progress at 54 Richardson Road but dog‑park hotspot remains

Consultants from Weston & Sampson gave the Select Board a four‑year progress report on cleanup work at 54 Richardson Road, saying the town’s remedial pump‑and‑treat system has removed mass from the original release and materially improved groundwater quality but that a separate contamination source near the dog‑park still requires additional treatment.

"We’ve made excellent progress," said Paul McKinley of Weston & Sampson, giving the board a technical update. He said the system, installed in July 2022, has pumped about 157 million gallons and driven concentrations down dramatically from a peak of roughly 1,400 parts per trillion in the source area.

The consultants described a multi‑pronged contamination profile: the primary on‑site release concentrated in the former eight‑bay garage area and a second, distinct source in the dog‑park area. McKinley said the dog‑park monitoring well is the most contaminated well still on the site and is not currently captured by the original treatment zone.

Linda Cook, McKinley’s colleague, walked the board through chemistry and monitoring trends and the consultants’ approach to distinguishing site sources from a broader regional background signal that the team said likely stems in part from decades of domestic septic inputs and ongoing consumer‑product emissions.

Key technical details the consultants reported: - The remedial system has been operating ~four years and pumped about 157 million gallons. - The original source well peaked near ~1,400 parts per trillion (ppt) for PFAS signature compounds and has fallen substantially under treatment. - One remaining dog‑park well is currently measured near 91 ppt and appears to be a separate source. - The PFAS6 metric and its current guidance level (20 ppt) have been used for site tracking, but the EPA is drafting much stricter levels (the presenters cited a potential 4 ppt MCL for PFOS/PFOA by 2031), which creates a higher regulatory bar for closure.

To address the remaining hotspot, the consultants proposed installing an additional recovery well in the dog‑park parking area and tying it into the existing treatment trains so the site’s treatment can expand its capture zone. McKinley said the town and consultants have already discussed trenching and construction coordination with DPW and expect to proceed with system expansion planning in FY27.

On the question of how the town would achieve regulatory closure, McKinley said the likely path is to treat the town’s source to background and then demonstrate no rebound after shutdown. "What we're going to do is shut it down and ... we'll have to do about a year's worth of monitoring," he said, explaining that an initial shutdown would be followed by a monitoring period to confirm stability.

Board members pressed the consultants on background PFAS contributions and the feasibility of reaching draft EPA goals. The presenters cautioned that regional background concentrations may already exceed the draft 4 ppt levels in parts of town because PFAS do not readily degrade and have entered groundwater over decades. They emphasized that the town’s immediate obligation is to treat the polluting source that originated at the 54 Richardson Road property while continuing to work with regulators on long‑term measurement and closure strategies.

The consultants said the remedial approach has already brought several downgradient monitoring wells below the earlier PFAS6 guideline and credited the system with preventing measurable impacts at nearby public‑supply receptor wells. They characterized the next concrete steps as adding the dog‑park recovery well, expanding treatment capacity, and continuing sampling and coordination with state regulators.

The board did not take any binding votes during the presentation; staff and consultants said they will return with scopes, cost estimates for the expansion, and a proposed FY27 capital request to implement the next treatment leg.