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NH Ball Bearings and consultants outline 2023 plan to install new PRB at South Municipal Well site
Summary
Company and consultants told the Peterborough Select Board they plan to install a 450-foot permeable reactive barrier of zero‑valent iron at 50–60 feet to treat groundwater contamination at the South Municipal Well; EPA is lead, the state supports the effort, construction is contingent on contractor availability, and monitoring is expected to take about two years.
Representatives from New Hampshire Ball Bearings and consultant Geosyntec presented a technical update Tuesday on remediation work tied to contamination of Peterborough's South Municipal Well.
Chris Rawnsley of New Hampshire Ball Bearings said the well was taken offline in the early 1980s after contamination that the company has since worked to remediate under oversight from the U.S. Environmental Protection Agency and the New Hampshire Department of Environmental Services. Rawnsley introduced a planned remediation measure known as a permeable reactive barrier, or PRB.
Rhiannon Scott of Geosyntec said the planned PRB will be about 450 feet long, installed at a depth of roughly 50 to 60 feet, and constructed of zero‑valent iron (ZVI). As groundwater flows through the iron media, contaminants react with the media and are rendered inert before the water exits the barrier, she said. Consultants said all construction will occur on NHBB property and that the roadway will not be closed, though short traffic delays are possible during delivery of equipment and materials.
Geosyntec and NHBB staff explained that a PRB installed in 2016 did not meet performance goals because of the installation method; the new approach uses a different installation method aimed at avoiding the prior failure mode. Officials said design approval and contractor selection are planned for February through April 2023, with construction targeted to begin in June 2023, contingent on contractor availability. They said it will take about two years of monitoring to determine whether the barrier is performing as intended.
Scott said some excavated contaminated soil will be mixed into the PRB media, and any remaining material will be transported to EPA‑approved facilities for disposal. Audience member Doug Ward asked what the next remediation method would be if the new PRB fails; Rawnsley replied, "I don't know if we've considered that yet." Valerie Jurgens, the EPA project manager, and Stephanie Monet, the New Hampshire Department of Environmental Services project manager, introduced themselves and said the EPA is the lead agency with state support and invited further questions.
