Saint‑Gobain has begun demolition at its Merrimack facility and plans to remove the entire above‑ground structure, leaving only the concrete floor and foundation, New Hampshire Department of Environmental Services (DES) staff told the commission on Dec. 13.

DES project manager Andrew (Andy) Fuller said Saint‑Gobain has already removed equipment related to PFAS emissions and that demolition work began with a one‑story “low bay” portion of the building. “They are planning to remove the entire above ground structure and leave only the concrete floor and foundation at the facility,” Fuller said. He told the commission contaminated demolition debris that is “significantly impacted with PFAS contamination” will be sent to an out‑of‑state hazardous waste landfill; Fuller said Saint‑Gobain identified a landfill in Pennsylvania to accept that waste. Fuller also said some scarified concrete and related material will be stockpiled on poly and shipped off‑site; he reported Saint‑Gobain staff indicated that some concrete material may be sent to Canada.

Why it matters: DES staff framed the demolition and debris handling as part of an ongoing remediation and monitoring program tied to a long‑running PFAS contamination response in Merrimack. How demolition, handling of contaminated soils and concrete, and long‑term monitoring are carried out will affect local exposure pathways and the timetable for community restoration.

Most important details

- Schedule and scope: Fuller said demolition began in October and that Saint‑Gobain anticipates completing demolition activities during 2025 as weather permits. Structural steel will be recycled as scrap; PFAS‑impacted demolition debris will go to a hazardous‑waste landfill out of state (reported example: Pennsylvania). Fuller said the company will scarify concrete floors (removing roughly one‑eighth to one‑half inch where coatings were applied) and stockpile and ship the removed material off‑site.

- Controls and oversight: Fuller described dust suppression measures for concrete scarification (wet cutting) and said contractors have been placing removed material on poly for off‑site shipment. DES has requested monthly status reports and said it will remain in frequent contact as decommissioning continues.

- Household water response and construction: Fuller reported installation of point‑of‑entry treatment (POET) systems for residences, with 679 POET systems installed as of Dec. 4. Saint‑Gobain and contractors (identified in the meeting as 2nd Wind and Culligan) are continuing construction of water‑line extensions and service connections in Merrimack and surrounding towns. Fuller said 55 residents in a Hillcrest Road water‑main extension area had their private wells disconnected and are receiving public water service; he reported 32 properties declined connection beyond the curb, 14 allowed a service line to be run to the house but did not connect, 10 did not respond to notices and 8 declined entirely. DES said a total of 18 curb stops were installed for properties that declined to connect at this time.

- Sampling and remedial planning: Fuller reported this sampling status: 3,867 properties were identified for sampling; 2,574 samples from water supply wells have been collected and 1,200 second samples have been taken. DES reported 1,166 properties exceeded the applicable standard and were offered bottled water. DES initiated sampling at roughly 86 previously unsampled properties inside the consent‑decree outer boundary; results were available for about 84 of those and DES reported roughly 10 percent of that group exceeded DES ambient groundwater quality standards (AGQS) and about 70 percent exceeded the EPA MCL referenced in the meeting record.

- Groundwater management permitting and remedial action planning: Fuller said Saint‑Gobain originally was asked to submit a groundwater management permit (GMP) application under DES rules but instead submitted a groundwater management zone work plan (late September) describing long‑term monitoring; DES provided preliminary comments and expects a revised work plan imminently. Fuller said Saint‑Gobain submitted an initial Remedial Action Plan (RAP) in May 2023, a RAP addendum in February 2024, and DES found both did not meet requirements under DES rules (letter dated Oct. 10, 2024). Saint‑Gobain told DES it will submit a further RAP addendum to evaluate additional remedial alternatives; DES said it had requested that submittal by the end of January 2025 but expects Saint‑Gobain to request an extension.

Voices from the meeting

Fuller (DES Hazardous Waste Remediation Bureau project manager) summarized the demolition and monitoring work and the company’s plans for waste disposition; he told the commission the demolition contractor was “putting [scarified concrete] on poly and stockpiling it, and they’re gonna be shipping that all off‑site as well to a lined landfill.”

Commission members asked for clarifications about off‑site destinations and protections. Commissioner Nancy Murphy asked whether scarified concrete would be removed out of state and raised concerns about airborne material; Fuller explained wet cutting and dust suppression and confirmed stockpiling and lined landfill disposal. Commissioner Don asked whether curb‑stop installations would let future owners connect without digging across a property; Fuller and others confirmed Saint‑Gobain will pay for a full connection if a homeowner elects to connect now and that in many cases contractors are running a service line toward a house even if the owner elects not to connect immediately.

What remains open

DES said it expects revised monitoring and remedial plans from Saint‑Gobain soon and that sampling, long‑term monitoring and RAP revisions will continue into 2025. DES also said it will continue to press for expanded sampling in the consent‑decree outer boundary and to negotiate the appropriate monitoring and response framework under its rules.

Ending note

DES emphasized the work is ongoing: demolition, off‑site disposal of contaminated debris, continued household POET installations and water connections, and additional sampling and remedial submittals from Saint‑Gobain are all expected to continue into 2025.