Study finds no risk from solvent near base
JOINT BASE CAPE COD — A study looking at the nature and concentration of a solvent detected in groundwater southwest of Joint Base Cape Cod has determined it does not pose a risk to public health.
Based on the conclusions of an investigation conducted by the Air Force during the past several years and contained in a supplemental report and fact sheet prepared in January and just released to the public, 1,4-dioxane “should not be considered a contaminant of concern” at the levels found during monitoring.
What remains of the compound should eventually dissipate through natural processes, the report concludes.
The investigation into the presence of 1,4-dioxane near the Falmouth section of Route 151 was prompted by a recommendation in a five-year progress report published by the base cleanup team in 2012, which focused on the removal of tetrachloroethene, also known as perchloroethylene, or PCE, from the groundwater southwest of the military base.
Although cleanup of the PCE progressed more quickly than anticipated, and the extraction wells were taken out of operation in 2015, monitoring for 1,4-dioxane in the area continued beyond that date.
An initial water sampling program that included 32 monitoring wells was completed between August 2015 and May 2016. The compound was detected at concentrations exceeding the Environmental Protection Agency’s “risk-based concentration” of 0.46 micrograms per liter in two of the monitoring wells, which then defined the area of focus.
Eight monitoring wells were sampled four times between March 2017 and May 2019. The compound was not detected in seven of the eight wells. The concentration of 1,4-dioxane fluctuated in that remaining well during the two-year period, from 0.2 micrograms per liter in November 2017 to 0.7 micrograms in May 2019, but an average of the results remained below the federal risk-based concentration standard.
The recommendation to take no action for the 1,4-dioxane was based on its presence in only one of the monitoring wells, which lie about 80 feet below the water table. “Concentrations in this area are expected to continue to decrease through the process of natural attenuation,” the report says.
It goes on to say, “The screening-level human health risk assessment concluded there is no unacceptable risk to current or future residents from 1,4-dioxane at the site under a drinking water exposure scenario.”
Although it was initially detected in a sample from Deep Pond, “concentrations are well below the ecological screening value for 1,4-dioxane,” the report says.
The EPA has agreed with the findings in the Air Force report, and the Massachusetts Department of Environmental Protection said it plans to provide its input after the 30-day public comment period ends Aug. 30.
According to Doug Karson, the Air Force community involvement lead on cleanup efforts at the base, public comments and responses to them will be incorporated into the report. “Our goal is to have the final report done by the end of our fiscal year, which is Sept. 30,” he said.
Joint Base Cape Cod has been used for military training since 1911, and munitions, unexploded ordnance and fuel spills related to that training contaminated groundwater under the base and in surrounding communities. The base was placed on the Superfund National Priorities List in 1989. Various investigations and cleanups of soil and water have been going on since the 1980s. The EPA and state Department of Environmental Protection have been involved in overseeing cleanup.
The chemical 1,4-dioxane is a clear liquid used as a solvent in the manufacture of chemicals. Historically, it has been used as a stabilizer in chlorinated solvents, paint, adhesives, pesticides and in household cleaners, detergents, shampoos, deodorants and cosmetics.
The state Department of Environmental Protection has set a drinking water guideline for 1,4-dioxane at 0.3 micrograms per liter.
The possible health effects, which could be the development of some types of cancer, depend on the level of 1,4-dioxane in the water and the length of time someone is exposed, according to the state agency’s website. “These values are set at a concentration in drinking water that would increase a person’s chance of getting cancer by one-in-a-million if they drank the water daily for a lifetime.”
Written comments on the Air Force report can be emailed to Doug Karson, AFCEC/JBCC, Attn: CS-20 Plume, 322 East Inner Road, Otis ANG Base, MA 02542-1320; or emailed to douglas.karson@us.af.mil. Voicemail comments can be left at 508-968-4678, ext. 2.
Follow Christine Legere on Twitter: @ChrisLegereCCT.