Agents say there is no immediate danger to residents, and water quality continues to meet state and federal standards
As part of the plan to test for the possible spread of groundwater contamination near the site where dry cleaning chemicals were found, the Environmental Protection Agency is expected to continue vapor sampling in Hockessin this winter.
According to EPA Region 3 spokesman Roy Seneca, EPA field representatives have contacted residents and business owners throughout the Hockessin area and began sub-slab indoor vapor sampling at selected locations for two days in January.
Sub-slab soil gas samples are used by the EPA to assist in the evaluation of indoor air quality, according to the EPA website.
Initial vapor intrusion sampling was completed Jan. 25, following two days of sampling; the EPA anticipates another round of sampling in about a month, Seneca said.
The sampling is being done in accordance with the EPA and Delaware Department of Natural Resources and Environmental Control’s (DNREC) ongoing efforts to mitigate groundwater contamination at Sunrise Cleaners, located at the Shoppes of Hockessin on Lancaster Pike.
In 2005, a variety of chemicals associated with dry cleaning processes were found in groundwater and soil samples collected by DNREC at the dry cleaning business.
Those chemicals were primarily Volatile Organic Compounds (VOCs), including perchloroethylene (PCE, or “Perc”) and trichloroethene (TCE), chemicals are commonly found in dry cleaning solvents and other industrial solvents and degreasers, according to the EPA.
PERC is classified as a Group 2A carcinogen, which according to the International Agency for Research on Cancer means the chemical is likely carcinogenic to humans.
The Sunrise site is also the part of ongoing air sparging efforts by water management company Artesian in an effort to remove the chemicals from the groundwater that supplies hundreds of wells in the Hockessin area.
Air sparging is a method of vapor dispersion that entails pumping air into underground wells and then dispersing the resulting vapor into the air.
The ongoing air sparging efforts at the Sunrise site are being conducted by Duffield Associates, and at the expense of the Shoppes at Hockessin’s owner, according to Greater Hockessin Area Development Association vice president Mark Blake.
Water is also treated at individual well sites with appropriate carbon filtration to remove VOCs, according to Artesian.
According to an EPA press release, the department began an environmental assessment in Hockessin in September 2016, which included soil vapor, groundwater and surface water.
As part of the investigation, they sampled existing municipal, irrigation, and residential wells in the area.
“The results indicated PCE and other chemicals were present in some soil vapor and groundwater samples,” the release states. “Mill Creek and other surface water samples did not indicate PCE and other chemicals at concentrations of concern.”
The results of the soil vapor testing generally did not suggest wide spread contamination or concentrations of PCE at levels that would present a risk, the release states.
Those 2016 sampling results were used to determine which residential and commercial buildings should be tested in the area for vapor intrusion as a precautionary measure.
Seneca said that based on current results of the environmental assessment at the Hockessin Groundwater Site, the EPA does not believe there is any immediate danger.
“EPA is currently conducting vapor intrusion sampling as a precautionary measure to confirm results of a soil vapor study conducted in September that found there were no concentrations of PCE in soil vapors that raised a concern,” he said. “Regarding drinking water, the treated water supply provided by Artesian Water Company continues to meet state and federal drinking water standards.”
EPA agents have collected vapor intrusion samples from four locations and will sample two other locations in roughly a month, according to Seneca.
Seneca said that the results of sampling will be made available to the public sometime in the spring.