DNREC, EPA reps say how the groundwater plume contamination will be dealt with will ultimately be determined by its federal NPL status

The discovery of a groundwater contamination in Hockessin dates back over a decade at this point and residents are wondering what has been done to mitigate the damage.

At the June Greater Hockessin Area Development Association meeting, representatives from the Environmental Protection Agency (EPA) and the Department of Natural Resources and Environmental Control (DNREC) revealed that the Hockessin area is being assessed as a possible Superfund site.

According to the U.S. Department of Health and Human Services, a Superfund site is any land in the country that has been contaminated by hazardous waste and identified by the EPA as a candidate for cleanup because it poses a risk to human health and/or the environment.  

The investigation stems from the discovery of groundwater contamination of a Volatile Organic Chemical (VOXC) called perchloroethylene, also known as PCE or PERC, a manmade, chlorinated chemical solvent used commercially as industrial degreasers, spot removers, and in dry cleaning.

At that meeting, DNREC representatives noted several possible sites for contamination, including three dry cleaners, and a former service station.

The Sunrise Cleaners at the Shoppes at Hockessin has been the focal point of an ongoing air sparging cleanup, where air is pumped into the groundwater and the chemicals released as harmless vapor.

According to EPA spokesman Roy Seneca, EPA’s role began in spring 2016 and has been essentially to collect information necessary to determine whether the site will qualify for proposal to the Superfund National Priorities List (NPL). 

During that assessment, Seneca said the EPA also evaluated situations that might require immediate action, as in the presence of vapor intrusion.

“[We] determined no threat was present at this time,” Seneca said of the vapor intrusion testing.

There are currently 21 NPL sites in Delaware, nine of which are located in New Castle County, according to the EPA website.

DNREC representative Michael Globetti said that majority of the resources allocated to this concern have gone to evaluating the extent and potential sources of contamination. 

“The level of the contamination identified at Sunrise warranted an immediate action and that is why the air sparging at this facility was initiated,” Globetti said. “Once the full extent of contamination has been identified and a feasibility study has been conducted to evaluate possible remedial actions, the applicable regulatory agency will select a remedy for the public to comment on.”

He added that both the Hockessin and Sunrise Cleaners potential responsible parties have entered into a Voluntary Cleanup Program (VCP) agreement with DNREC to investigate their properties and are working on evaluating possible remedial actions that may be required. 

Regarding options for treatment, Globetti said that DNREC and EPA are still evaluating possible remedial actions that would address the groundwater contamination for the long term. 

“[Public water supplier] Artesian already has a carbon treatment system on the affected wells to ensure the drinking water provided to their customers meet all federal and state drinking water standards,” he said. 

Seneca said that if the site formally listed on the NPL, EPA will then conduct a Remedial Investigation and Feasibility study to further determine the nature and extent of the contamination and then evaluate various treatment options.

“There are many treatment options for treating this type of contamination that would have to be evaluated,” he said. “EPA will then develop a Proposed Plan for cleaning up the site that would be announced in a public notice. This would be followed by a public comment period before a final decision is made on a cleanup plan.”

On future treatment of the overall contamination, Seneca said it’s too early to tell how it will be dealt with because the site has yet to be proposed to the NPL.

If and when that happens, EPA will publish a public notice in the Federal Register and then issue a public notice through the local media to notify the community so those interested can comment on the proposal, Seneca said.

“EPA then responds to comments received.  If, after the formal comment period, the site still qualifies for cleanup under Superfund, it is formally listed on the NPL,” he said.

For more information, visit epa.gov/superfund/about-superfund-cleanup-process#tab-2.