Concord oversight committee urges clearer EPA explanation, more bedrock wells after groundwater report

The Town of Concord oversight committee on March 27 approved draft minutes and resolved to file written comments with the U.S. Environmental Protection Agency on the annual groundwater report after members raised technical concerns about bedrock contamination and monitoring.

The committee’s discussion focused on questions about piezometer siting, year‑to‑year differences in groundwater flow figures, and a detailed presentation from a technical expert who said the bedrock 1,4‑dioxane plume is not well constrained. The presenter pointed to one bedrock monitoring well, identified in the report as MWBS32, that recorded 26.6 micrograms per liter of 1,4‑dioxane in April 2025, up from 8.8 µg/L the previous year, and recommended additional wells on the northern side of the river to define the plume’s edges.

Why it matters: committee members said better characterization of the bedrock plume matters for public‑health oversight and for understanding whether contamination could migrate toward municipal wells or other sensitive receptors. The group also discussed public messaging for an upcoming EPA update, and whether a committee representative should briefly introduce EPA’s presentation to emphasize the extent of cleanup already completed and the community’s priorities for reuse.

The committee asked EPA for clearer interpretation and hypotheses in future reports, and sought a plan that would test whether observed variability arises from groundwater‑level changes, pumping rates or other hydrologic processes. “We don’t really understand the bedrock picture yet,” the presenter told the committee, adding that the report’s contours appear tightly drawn around a single high‑value well and could bulge into unconstrained territory without additional data.

Members highlighted specific technical and scheduling points they want reflected in comments to EPA: that a broader 2026 sampling campaign will include more wells; that PFAS sampling is being added on a five‑year cadence with expanded wells planned for 2026; and that the EPA’s current internal timeline lists the site as likely reaching a ready‑for‑reuse determination in 2031. Committee members asked staff to prepare concise bullet points for the public meeting and to add a short FAQ to the committee’s website summarizing monitoring results and reuse expectations.

The committee also flagged language and framing for the public meeting. Several members urged plain English explanations and suggested the committee chair or a designated committee spokesperson introduce EPA’s presentation so the public hears both what EPA has done and how the town is interpreting those results for future reuse. One member summarized the outreach aim: to stress that much cleanup work has been completed while acknowledging remaining uncertainties.

Next steps: volunteers agreed to draft the committee’s written comments to EPA (the committee noted the comments deadline is Monday) and to meet again if slides from EPA require last‑minute tweaks ahead of the public update. The committee noted an invitation‑only technical preview at the site on March 27 from 10 a.m. to noon and a public presentation planned for the following week at Town Hall (229 Main Street), with Teams access for remote attendees.

Formal action: the committee approved draft minutes for Oct. 17, Jan. 9 and Feb. 20; the minutes motion was moved by the Chair and seconded by a committee member and recorded as approved (individual roll‑call tallies were not specified at the meeting).

Reporting note: quotes and technical claims in this report are drawn from the committee meeting discussion and the presenter’s screen‑share of figures and monitoring data. The committee’s written comments to EPA, when filed, will provide the formal record of the questions and requests described here.