PFAS sampling prompts expanded disposal boundary; several homes offered town water connections

The Nantucket Memorial Airport Commission received an update Feb. 11 on an ongoing PFAS investigation at and west of airport property, including new sampling, expanded disposal‑site boundaries, monitoring‑well installations and a Phase 3 remedial alternatives study the airport expects to file with MassDEP.

Environmental coordinator Cameron Woods told the commission the airport has transitioned ARFF trucks to a fluorine‑free foam system and posted an IFB for converting two trucks that must be sent off island. Woods introduced Jim Soukup, the licensed site professional from Western Solutions, who summarized supplemental sampling and next steps.

Soukup said a phase‑2 addendum prepared after the EPA lowered its lifetime health advisory level prompted an expanded disposal boundary to include additional airport‑owned parcels. Teams resampled approximately 20 homes on the West Side that were within or abutting the expanded boundary; initial sampling was completed in September and a follow‑up round occurred in December. Of the original targeted properties, Soukup said 4 homes exceeded applicable screening levels in the team’s review (three exceeded the MassDEP groundwater standard of 20 parts per trillion and one exceeded the EPA MCL of 4 ppt). The airport provided bottled water to affected households immediately and offered town‑water connections to homes within the disposal boundary that had any PFAS detection, Soukup said.

"We offered connection to all homes that are within the disposal site boundary that had any detection of PFAS," Soukup said.

Soukup said signatory PFAS signatures were used to distinguish the airport source from a separate Pine Tree Road source. Two West‑side homes with detections between 4 and 20 ppt showed a Pine Tree signature rather than the airport signature; three detections that exceeded MassDEP levels had at least partial airport signatures. Property owners were notified immediately, laboratory reports were shared, and the airport supplied bottled water and then scheduled connections to town water for qualifying homes. Soukup reported that several residents declined access requests and would not be sampled after repeated attempts.

The team installed eight off‑site monitoring wells in December to better define groundwater flow on the West Side; one of those wells was placed inside the airport fence where road work made placement outside the fence impractical. Groundwater elevation measurements and a spring sampling round are planned to better define flow direction and concentration trends.

For long‑term cleanup the LSP said the Phase 3 evaluation — due to MassDEP by March 3 — analyzes remedial alternatives for soil and groundwater, including monitored natural attenuation, capping, excavation with on‑site or off‑site treatment, relocation and treatment of geothermal extraction/injection systems, expanded pump‑and‑treat systems, and in‑situ treatment (injection of activated carbon to create treatment curtains). Soukup said the Phase 3 will balance effectiveness, implementability and cost and will identify a preferred alternative for subsequent design work.

Soukup and commissioners discussed the role of the airport’s geothermal (open‑loop) system and whether treating or relocating that system could reduce spread of contamination to the west. Commissioners requested the IRA status report (due at month end) and the Phase 3 alternatives report; staff said both will be available for the March meeting and that the IRA status report will be the comprehensive document to share with town officials.

Commissioners asked for clear communications to the town about the results and steps taken; staff said letters and laboratory reports were sent to homeowners who had detections and that a full IRA status report will document maps and recommended boundary changes for formal submittal to MassDEP.