Restoration of the contaminated land on and around the hill north of Hartwell Road continues at a speed somewhere between painstaking and glacial.
That summarizes the annual update delivered at last week’s hearing of the Restoration Advisory Board for the former Naval Weapons Industrial Reserve Plant.
Representatives of the contractors employed by the government to restore the site did confirm that underground water contamination, present for more than 50 years, is not threatening residential neighborhoods or playing fields.
This Restoration Advisory Board is a Department of Defense practice, comprising stakeholders to “discuss environmental restoration at a specific property” at which the department oversees cleanup efforts.
The 30 acres on and around the Hartwell Road hill, as well as 16 acres on the other side of the street, have been on the federal environmental remediation list known as the Superfund for almost 30 years. The Navy retains responsibility for environmental remediation on the entire 46 acres, regardless of ownership.
Almost a year ago, the Navy implemented what it called a “time-critical removal action” on the east side of the area, as a contaminated groundwater plume was thought to be migrating in the direction of residential areas beyond the perimeter.
In answer to a question from resident Christopher Boles at last week’s hearing, Rob McCarthy of the firm Resolution Consultants said the plume remains under evaluation but “does not appear to be advancing.” McCarthy said when the area was verified, contractors installed 20 monitoring wells at two different depths “to manage potential migration.”
The contaminants are located “essentially where we installed the new wells,” McCarthy said. “We have not identified any risks.”
According to the Navy’s presentation, additional sampling and hydrogeologic data from December and January are under review. Plans call for injections later this year of a product called LactOil, described as “a soy microemulsion similar to vegetable oil” that is intended to “augment natural attenuation.”
Jennifer Boles, who in 2021 chaired a Selectmen’s ad hoc committee exploring possible uses if the Navy divests the area, asked about the proximity of a plume of contaminants to the playing fields west of the site. There’s no presence beyond the boundary of the site, said Paul Probasco, representing another contractor, Tetra Tech. Eric Ross, the Navy’s regional project manager, added, “That’s one area we regularly monitor.”
Mitigation is aimed at two areas on the 30-acre site. One is an underground plume in which the primary groundwater contaminant is trichlorethylene (TCE). The other area is a plume of benzene, toluene, ethylbenzene, and xylene. For that site, the original cleanup target date of 2018 was extended by 10 years. Ross said, “we still think that will close within the next 10 years.”
The Navy, through its contractors, employs a number of processes and steps to address the contamination.
A groundwater treatment system has been operating in the area designated as Site 3 since 1997, extracting from 23 wells. The water is processed through carbon to remove volatile organic compounds and discharged to the ground. Steve Passafaro of Sovereign Consulting said the system is extracting less than a pound of the compounds per month.
Paul Probasco, who works for Tetra Tech, said “there is a component of TCE and 1.4 dioxane to the north that we want to be able to better capture. Construction of an expanded extraction system – 28 additional wells – is expected to get underway early next year, he said.
In the summer of 2021, the system was upgraded with an advanced oxidation process, Passafaro said, to remove the contaminant 1.4 dioxane. Last year, technicians added injections of LactOil.
In answer to a question from Board of Health member Ann Kiessling, Probasco said the soy-based vegetable oil injections “degrade better in a more anaerobic environment that is rich in carbon to enhance the naturally occurring bugs in an oxygen deficient environment. The aim is to remediate more efficiently.”
Other mitigation measures include evaluation for potential emerging chemicals, and periodic monitoring and reviews.
Part of the mitigation effort takes place with groundwater on acreage south of Hartwell Road, known as the southern flight test area that was divested by the Navy in 2019 and now is part of the site for a proposed major hangar development at Hanscom Field. The chemical compounds known as PFAS have been detected in groundwater there, and monitoring continues.
Select Board member Emily Mitchell, the town’s representative on the Hanscom Field Advisory Commission, noted that plans call for underground fuel storage on the site. She asked if that would interfere with remediation efforts.
McCarthy said land-use controls on the site do not prohibit fuel storage. “New tanks are not expected to have leaks,” he said.
In answer to a question, Ross said he had no concerns about the impact of the planned hangar project on the remediation effort.
“Whatever they do they will have to make sure we continue our work,” he said. “All agencies are reaching out to the developers to get as much information as possible.”
Jennifer Boles noted that there are plans for an aviation support building on the area south of Hartwell Road. She asked if there would be a problem with sleeping quarters in that facility. “That’s something that would have to be evaluated,” said Randi Augustine of the state Department of Environmental Protection.
A separate panel for many years has been addressing several contaminated sites around Hanscom Field.
Ross noted that trespassers continue to try to access buildings on the site, despite audible warnings and camera surveillance. Windows and doors have been sealed with 12-foot sheets of metal.
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