DES outlines demolition, sampling and long-term remediation steps at contaminated Saint Gobain site

The Department of Environmental Services provided a progress update Jan. 10 on demolition and cleanup work at the Saint Gobain facility and on related drinking water remedies for affected households.

DES said the company has dismantled portions of the building and received town permits for three demolition phases; contaminated materials will be sent to out‑of‑state hazardous waste disposal where required, and structural steel will be recycled, DES representative Mike said. "They completed asbestos abatement and PCB remediation in other parts of the building and applied for demolition permit with the town, in December for the remaining portions of the building," Mike said.

DES staff emphasized that demolition is separate from the remedial strategy to address contaminated soil and groundwater and that the agency expects substantial remedial proposals that reduce the mass of PFAS at the site. "We have made it very clear to them that we expect them to undertake remedial activities that will have a significant and meaningful impact in reducing the mass of contamination that is there," Mike said.

Why this matters: thousands of properties were targeted for sampling and hundreds of homes have received point‑of‑entry treatment (POET) systems or bottled‑water offers; the outcome of the site remediation and monitoring will affect long‑term drinking water safety and potential future connections to municipal water.

Most immediate actions and status

- Point-of-entry treatment: DES reported that, as of Jan. 8, 686 POET systems had been installed under the approved plan.

- Waterline construction: Contractors have completed or substantially completed water main extensions in Litchfield, Bedford and Merrimack; 55 residences in one project have been disconnected from private wells and now receive public water. The report said 32 properties declined connection; at some properties contractors installed curb stops without completing interior connections.

- Residential sampling: DES said 3,868 properties were identified for sampling (one more than November). Of those, 3,855 access agreements were sent with a roughly 73% return rate; 2,576 samples have been collected. Second samples have been collected at about 1,206 properties (about 95% of targeted resamples), and laboratory results indicate 5–10% of those resampled properties produced values above the applicable drinking‑water standard, triggering bottled‑water offers from the company.

- DES sampling of unsampled wells: DES began its own sampling in March 2024 for properties the company had not offered to sample; about 86 residences have been sampled in that DES effort, with roughly 10% showing exceedances of the current ambient groundwater quality standard and 70% exceeding the newly promulgated EPA maximum contaminant level (MCL), DES said. DES reported 66 property owners have not responded to sampling invitations and one declined.

Groundwater management permit and remedial planning

DES described an iterative process with the company on the groundwater management permit application and a remedial action plan (RAP). The agency said a RAP was submitted in May 2023, and subsequent addenda did not meet DES requirements in an Oct. 10, 2024 letter. The company has since proposed further addenda and a revised monitoring work plan; DES said it expects to issue formal comments before the end of January. "We expect there'll be a year or two of this work, and then a groundwater management permit application would come on the heels of that," Mike said.

Demolition and contaminated concrete

DES said the site foundation is unusually thick because of the facility's original industrial use; contractors are scarifying (removing thin surface layers) and conducting confirmatory sampling. Where scarification left contamination above standards, DES said the company will perform additional scarification. "There are a few areas where PCBs got into the concrete and they scarified that area," Mike said, noting some locations required extra work.

Remedial options discussed

Commission members asked about capping versus active remediation. DES said capping could reduce new infiltration but would not address contamination already in saturated soils and groundwater; the agency described excavation and off‑site disposal or groundwater extraction and treatment as common mass‑removal approaches. "We have very effective means of treating groundwater and water that's contaminated with PFAS. Remove that PFAS and reinject the treated water back in the ground," Mike said.

Ongoing oversight and next steps

DES said it will continue site visits and requested periodic status updates; it also is reviewing an extensive set of attachments to the company's remediation proposals. The department indicated demolition and remediation activities could take a large portion of 2025. DES also noted negotiations and coordination with towns and utilities on waterline extensions, and the Drinking Water and Groundwater Trust Fund Advisory Commission has approved an $8,000,000 grant to supplement town and company contributions for a Londonderry project.

Ending note

DES officials urged more robust remedial proposals to reduce contaminant mass rather than only short‑term or surface measures. Commissioners and members of the public raised questions about long‑term liabilities such as whether the company could be required to pay ongoing public water bills; DES said that would be a policy decision for the legislature and not a current DES enforcement requirement.