EPA: Libby groundwater five‑year review finds institutional‑control gaps; PFAS and lower‑aquifer data delay protectiveness determination

The U.S. Environmental Protection Agency told the Libby City Council that its five‑year review of the Libby groundwater remedy identified gaps in institutional controls and outstanding data that prevent a final protectiveness determination for the site.

Jason Rafy, the EPA project manager for the Libby groundwater site in the agency’s Helena office, presented the draft five‑year review, telling the council the review is a statutory assessment that asks whether the remedy is performing as intended, whether exposure assumptions and cleanup values remain valid, and whether new information calls the remedy’s effectiveness into question. "The five‑year review evaluates remedy performance and whether the remedy is protective of human health," Rafy said.

The draft review finds that the remedy for operable unit one (the human‑exposure pathway) is currently short‑term protective but that notable gaps remain because deed restrictions and the municipal well ban do not cover all properties across the contamination boundary. For operable unit two (source areas), the EPA marked the protectiveness determination as "deferred" pending results of additional study of the lower aquifer and a targeted investigation for per‑ and polyfluoroalkyl substances (PFAS). Rafy said the sitewide protectiveness determination follows the lowest applicable OU determination and is therefore also deferred.

Rafy described remediation history and current work: historical soil excavation (about 45,000 cubic yards removed and treated on a land‑farm/CAMU), prior groundwater treatment systems that were replaced or modified, and a new in‑situ biosparging (ISB) system intended to inject oxygen gas to stimulate biodegradation. He said the ISB is under construction for the upper aquifer, with Area 1 (about 36 injection wells near the former waste pit) scheduled to start operations in spring and Area 2 forming a barrier across the plume. "We will be starting up the ISB for the new biosparge remediation for area one; we expect that to go online in the spring," Rafy said.

The EPA said it has treated substantial volumes of contaminated water and removed creosote, but that the lower aquifer had been deferred from earlier decisions because a practical treatment technology was not available at the time. The agency is preparing a five‑year review addendum focused on the lower aquifer and PFAS sampling. Rafy explained that the PFAS concern stems from historical use of firefighting foams at waste pits and the potential for PFAS to be present in site materials.

Council members pressed EPA on whether recent well installations had changed plume characterization; Rafy said the new monitoring wells improved understanding of the upper‑aquifer plume but had not yet changed the overall plume characterization. When asked whether technologies used at other sites could be applied to Libby’s lower aquifer, Rafy said that any new remedy would require evidence the existing institutional controls and remedy are not protective and would trigger a full re‑evaluation and remedy selection process.

During the public‑comment period, a resident identified as Mr. Or sharply criticized EPA’s handling of the site, saying the agency "dropped the ball" by permitting industrial well drilling and alleging the city and agency negotiated settlements that did not adequately compensate residents. EPA did not provide on‑the‑record rebuttal during the meeting; Rafy’s public remarks focused on the review findings and next steps.

Next steps described by EPA include completing the five‑year review addendum for the lower aquifer and PFAS investigations, continuing ISB startup and monitoring, seeding the land‑farm and moving toward CAMU closure, and filling gaps in institutional controls (additional deed restrictions and well restrictions, including properties outside city limits). The EPA indicated timelines will depend on the PFAS investigation and lower aquifer evaluation and did not provide a firm completion date for the addendum.

The presentation and questions occurred during the council’s new‑business agenda. Council members asked for continued updates as the addendum and PFAS work proceed.

The EPA presentation began as the council’s new business item and concluded with a Q&A and public comment; the agency said it will complete the addendum as data permit and return results to the community.