The Conservation Commission on Wednesday gave the go-ahead for the U.S. Air Force to install monitoring wells and obtain soil borings to detect the possible presence of contaminants – including chemicals known as PFAS – in the Shawsheen River watershed.
The work, part of a contamination remediation on and around Hanscom Field that began in the 1980s, is expected to take place before the end of February.
“We have plans for two monitoring wells and one soil boring in the Hartwell Town Forest and one soil boring in the George Jordan Conservation Area,” said Matthew Greenberg, a civil engineer who serves as remedial project manager, in an email on Thursday.
“The objectives of the soil borings are absolutely a follow-up to baseline groundwater sampling event, to sample for and determine presence and concentration of PFAS in groundwater,” he explained.
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.”
Awareness of the threat of PFAS in the environment has grown in recent years, and town officials stopped drawing from the Bedford wellfield on Shawsheen Road in 2018 after testing confirmed the presence of PFAS in the water.
There has been much speculation that the chemicals originated at the airport, since they were components of a firefighting foam used during drills in the runway area when the Air Force operated Hanscom Field in the 1950s and ’60s.
Hanscom was listed on the U.S. Environmental Protection Agency’s cleanup priorities list in 1994. The Air Force, in a 2009 agreement, agreed to perform cleanup and investigations with oversight by the EPA, in cooperation with the Massachusetts Department of Environmental Protection.
Greenberg said Thursday that the new monitoring wells will be part of a continuing effort to determine the spread of “volatile organic compounds” in groundwater from the contamination sites. The wells also “will be available for PFAS sampling as needed,” he added.
The Conservation Commission approved an access agreement stipulating that the Air Force assumes responsibility for any damages and will make necessary repairs.
Commission members joined Greenberg and others involved with remediation on a site walk in late November to identify well and boring locations. “We tried to select locations using existing trails and access walkways to minimize clearing,” Greenberg told the commission.
Greenberg reported that the drilling equipment will be mounted on a rig with tires that are tracked like a Bobcat or similar to an all-terrain vehicle. Just before the project begins, he said, there will be reconnaissance for any problem areas. “We are very conscious of muddy areas and rutting that can result,” he said, describing the “mud mats” that could be used like a temporary bridge during access.
“We won’t need to do any tree removal if the swaths stay as they are, and damage should be minimal. We always try to avoid taking out vegetation,” Greenberg said, especially larger trees.
In his email on Thursday, the engineer explained, “The depths vary, depending on the objective of the particular soil boring or monitoring well. The soil borings will advance to bedrock, anticipated to not be deeper than 100 feet below ground surface total. The monitoring well depths will advance into bedrock and may be as deep as 130 feet below ground surface.”
Greenberg said if the work can be done in January or February, the ground should be frozen and thus the process should “avoid the ruts and clearing of vegetation. There’s no undergrowth right now.”
Commission member Frank Richichi noted that there have been periods of rain and the ground tends to freeze later than it used to, so he urged caution in accessing the sites. “When the time comes maybe some of us could check for standing water and other things that could lead to damage,” he said.
Jeffrey Summers, the town’s conservation administrator, noted that the agreement requires two weeks’ notice before any equipment is brought in “so we have time to document the area and be present.”
Richichi added that distance runners and even teams work out on trails traversing the Town Forest, and Greenberg said warnings will be posted at trailheads during the process.
“If and when we need additional locations, we will send maps and mark locations and conduct another site visit,” Greenberg said.