Environmental contamination administrator reports MassDEP source‑discovery results: 63% detect rate, nine imminent‑hazard wells on Tom’s Way cluster

Andrew Shapiro, Nantucket’s environmental contamination administrator, gave an expanded PFAS update that incorporated MassDEP’s recent source‑discovery sampling, local voluntary testing and a new Verdantas field investigation summary for the Fairgrounds site.

Shapiro said MassDEP evaluated 86 properties as part of its source‑discovery investigation and found PFAS detects at 63% of those parcels. He said 23 properties exceeded Massachusetts’ PFAS‑6 standard (20 nanograms per liter [ng/L], or parts per trillion), and identified nine properties — clustered on Tom’s Way and adjacent streets — that exceeded the state’s imminent‑hazard level of 90 ng/L. The maximum concentration reported in MassDEP data was 787 ng/L at a Tom’s Way location.

Shapiro stressed he tabulated MassDEP findings at the parcel level for clarity: some properties had multiple samples (initial, duplicates, post‑treatment and confirmatory results) so counts summarize by property, not by sample. The MassDEP data generally show higher rates and higher concentrations because their sampling is targeted to suspected source areas; the town’s voluntary and Board of Health regulation sampling is more distributed and tends to identify lower concentrations outside targeted zones.

Shapiro also summarized the Verdantas field investigation for the Fairgrounds Campus (report dated March 27). Key Verdantas conclusions Shapiro read included: (1) surficial soil PFAS6 concentrations were relatively low and distributed evenly with no clear surface source; (2) the highest groundwater PFAS‑6 concentration detected in that investigation was 22.33 ng/L at a monitoring well behind the Public Safety Complex; (3) groundwater PFAS‑6 was not detected at monitoring wells farthest to the west and southwest; and (4) groundwater flow at the investigated area appears generally northerly toward Old South Road with a minimal hydraulic gradient.

Shapiro said MassDEP conducted additional sampling on April 9 (three Mid‑Island properties and three west‑of‑town properties) and that MassDEP’s targeted approach explains the higher frequency of exceedances in their dataset. He cautioned the datasets are not perfectly comparable because sampling methods and lab methods differ: the health‑department drinking‑water tests use EPA Method 537.1, MassDEP’s drinking‑water samples use EPA 533, and the Fairgrounds groundwater sampling used EPA 1633 (a groundwater method that tests a wider PFAS suite). Shapiro noted reporting limits and method differences can affect detection and comparability.

Shapiro announced the town’s updated PFAS well‑sampling fact sheet is now on the town website and summarized key changes: encouraging consultation with doctors at all levels of detection, recommending confirmation testing after treatment installation, including streamlined reporting and contacts for concentrations above 20 ng/L, and providing an option to pursue treatment for concentrations below 20 ng/L. Board members pressed Shapiro to strengthen the fact sheet language that currently frames concentrations below 20 ng/L as a lower‑priority action, reminding staff that no PFAS level is known to be completely safe and urging clearer guidance about cumulative exposure risks. Shapiro and the director agreed to revise the fact sheet to emphasize there is no known safe PFAS level and to improve clarity about nondetect limits.

Shapiro said the town has engaged TRC for fingerprinting analysis and contracted TRC for additional PFAS work approved by the Select Board; those reports are pending. He outlined an expanded communications plan (social media posts, newsletter, newspaper article, fact sheets and public meetings) and said he will follow up directly with residents who receive detect results. The water company reported it will pour concrete for a new treatment system in the coming week.

Board members and staff discussed testing frequency and reporting: MassDEP guidance recommends annual routine tests for private wells and PFAS initial testing plus decadal retesting for PFAS unless located near known PFAS sources, where more frequent testing is advised.