Public comment period open until March 19

Although plans to place Hockessin on the Environmental Protection Agency’s National Priorities “Superfund” List move forward, it could be years before any action is taken.

The official proposal came last month – a move approved by the Delaware Department of Natural Resources and Environmental Control – in an effort to seek additional assistance and funding for the ongoing cleanup to the Hockessin Plume Contamination Site.

Placing the site on the NPL will accomplish that goal, putting control of the cleanup in the EPA’s hands, and providing additional federal funding for the site.

The process is currently in a 60-day public comment period that ends on March 19.

The EPA held a public information/Q&A in Hockessin on Tuesday, Feb. 13, covering the background behind the contamination of Perchloroethylene (PERC) that has reached the Cockneysville Aquifer, which supplies drinking water to the region.

PERC is a known carcinogen that is still in use as a dry cleaning solvent, although bans have been suggested or are in the works in individual states.

The contamination is believed to date back several decades, involving a number of potential sources, including two dry cleaners and several former gas stations.

According to the EPA, water supplier Artesian first detected PERC in their samples in 2001; those findings were in turn submitted to the Department of Health and Human Services.

For the past year and a half, DNREC has been working on mitigating the contamination via “air sparging,” where air is pumped into the groundwater, and the resulting vapor filtered and released harmlessly into the air.

That project is scheduled to end sometime in 2018, according to DNREC.

According to an Artesian spokesperson, samples from water supplied to their customers now fall below the state allowed 1 parts per billion (PPB) of PERC, noting the federal standard is 5 PPB.

EPA Remedial Project Manager Randy Sturgeon, who is assigned to the site, said that once the plume site has been added to the NPL, a feasibility study will determine how to further proceed with cleanup.

He also said there’s very little chance of the site not making the list, and urged residents to note in their comments if they wished to see it added.


Center for Disease Control’s Agency for Toxic Substances and Disease Registry (ATSDR) senior toxicologist Karl Markiewicz reiterated comments from previous sessions that the presence of PCE in the Hockessin area is not an immediate threat to public health.

When asked about increased incidences of cancer in surrounding communities, particularly around Millcreek Road, Markiewicz noted the national average of 1 in 2 men and 1 in 3 women contracting cancer.

“It’s not uncommon to see a lot of cancers on a street,” Markiewicz said. “Age is also the number one risk factor, so if there is an aging population, you’re going to see more cancers there.”

He added that the carcinogens in PERC primarily manifest as bladder cancer, and not random other forms of the disease.

“Part of this whole process when a site is listed or proposed on the NPL is that we are required or mandated to write what we call a ‘Public Health Assessment,’” he said. “We will look at what environmental concentrations there are out there, and look at the exposure pathways, and do an evaluation as to whether adverse effects could have occurred or not.”

To date, that assessment has not been performed, according to Markiewicz.

A 2016 article from on household solvents, however, said that exposure to PERC has been shown to cause liver tumors in mice and kidney tumors in male rats, citing studies by the Center for Disease Control’s Agency for Toxic Substances and Disease Registry.


EPA spokesman Connor O’Laughlin said that following the public comment period, the EPA would determine whether or not to place the site on the Superfund list using a variety of factors.

Once its status is determined, a Feasibility Study will be performed to establish cleanup methods, with the ultimate goal of having the site removed and delisted from the NPL.

“The ultimate goal is to foster safe reuse of the affected land,” O’Laughlin said.

He also noted that while the EPA has been hit with funding cuts by the federal government, those cuts are unlikely to affect any Superfund site.

“The NPL list is a priority,” he said.

Sturgeon said that even once the site makes the list, it could be three years before any action is taken regarding cleanup.

Comments can be submitted online or via mail.

Online, visit

Via mail: US EPA Docket Center, NPL Notice of Proposed Hockessin Groundwater Site, Docket ID# EPA-HQ-OLEM-2017-0604, Mail Code 28221T, Pennsylvania Ave. NW, Wash., DC, 20460.

For more information on the Hockessin site, visit