Much of the focus of the ongoing US Air Force environmental cleanup at Hanscom Field hazardous waste sites has turned to PFAS, a chemical category that was not identified when the process began years ago.
Details were shared at the annual meeting of the Hanscom Restoration Advisory Board, which was established to keep the public informed and involved with cleanup and restoration.
The annual environmental restoration program update was held virtually, and most of the attendees were from federal agencies and the contractors supporting them.
Contamination was identified decades ago at various locations, tracing back to when the entire facility was an Air Force installation.
There are five sites monitored under the federal Comprehensive Environmental Response Compensation and Liability Act (CERCLA), with three of them geographically within Bedford, around the runways. They were used for fire suppression training and paint disposal in the late 1960s and early ’70s.
The other two-the former base landfill capped in 1988 and a one-time airplane fuel distribution area shut in 1973-are on the southern part of the airfield, but that section drains into the headwaters of the Shawsheen River. Also, the former base gas station and repair shop is a state hazardous waste site monitored annually.
PFAS contamination was identified relatively recently in the United States. Indeed, when the chemicals were confirmed at Hanscom, Bedford officials deactivated the Shawsheen Road wells as a precaution, even though levels of the chemical were within federal safety standards. So for the past couple of years, all of the town water has emanated from the metropolitan system.
PFAS is an abbreviation for per-and polyfluoroalkyl substances. According to the Environmental Protection Agency, PFAS “are a group of manufactured chemicals that have been used in industry and consumer products since the 1940s because of their useful properties… Scientific studies have shown that exposure to some PFAS in the environment may be linked to harmful health effects in humans and animals.”
Matthew Greenberg, the Air Force’s restoration program manager, told the virtual meeting that “regulatory standards are still evolving” for the chemicals. He said PFAS has been connected to the firefighting foam used for years in the runway area, most of it during drills.
A 30-year-old groundwater treatment plant north of the long runway, installed as part of the restoration effort, is discharging effluent with PFAS concentrations above the federal limit, Greenberg confirmed. The facility treated more than 30 million gallons of groundwater in the year beginning in September 2020.
The system was not designed for PFAS removal, he said, and “a project is underway to evaluate the best way to upgrade.”
“Doing anything to modify that system could take a bit of work,” he said, acknowledging that even higher standards in the future could supersede that remediation.
Site inspections have focused on the extent of migration to the town’s deactivated Hartwell Wells, as well as the Jordan Conservation Area behind Hartwell Road and adjacent to the Town Forest. He said fieldwork won’t be finished until next month
Greenberg said that although unacceptable levels of PFAS were identified in 2018 site inspections, there were “no pathways to drinking water.”
The response included a survey of a broad area downstream to identify wells used for drinking water. The “polygon” terminated at The Great Road near the confluence of Elm Brook and the Shawsheen. No active wells were found.
Heidi Porter, Bedford Health and Human Services director, wondered why the survey didn’t continue downstream to the Shawsheen Road wellfields, about 1,500 yards away. Greenberg said The Great Road was “a geographic cutoff.” He said future investigations likely will include additional “pathways,” noting, “The well survey was an intermediate step to see if there are any immediate mitigation needs.”
Remedies put in place in 2007 for the range of contaminated sites included land-use restrictions, a sampling program with five-year reviews, institutional controls like signage, and continued operation of the water treatment plant.
The chemical dioxane was confirmed as an additional contaminant in 2019, not only in surface water but also lower/till and bedrock aquifers, he said. Nine wells were drilled to expand monitoring.
Mike Rosenberg can be reached at [email protected], or 781-983-1763
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