The Hockessin Groundwater Superfund site sits in a mixed commercial and residential area in Hockessin, Delaware. The State of Delaware first flagged potential contamination in 2002, after the Artesian Water Company found contaminants in untreated water. EPA added the site to the National Priorities List in May 2018, making it eligible for federal cleanup funding. Two dry cleaners in the area contributed to the contamination, and other sources may also exist.
The main contaminant is tetrachloroethylene, also called PCE, a solvent widely used in dry cleaning and metal degreasing. PCE has contaminated groundwater and soil beneath the site. Three municipal wells, three residential wells, and one irrigation well show contamination above drinking water standards. The Artesian Water Company serves about 184,000 people, with roughly 10,500 potentially affected by the contaminated wellfield. The water company treats the groundwater before distribution, and finished drinking water meets all federal and state standards. Delaware has also installed carbon filtration systems on the three residential wells. A vapor intrusion assessment conducted starting in fall 2016 found low impact to indoor air.
The site is divided into three active operable units, or OUs. OU 01 covers the broader groundwater plume, with a combined remedial investigation and feasibility study underway since August 2019. OU 02 covers the Hockessin Cleaners area, where EPA completed a thermal treatment project on June 11, 2025. That four-month project used heat to pull PCE from soil and groundwater, with vapors safely disposed of under state and federal rules. Sampling confirmed reduced contamination in both soil and groundwater. OU 03 covers the Sunrise Cleaners area, where EPA removal activities wrapped up in March 2022. No cleanup decision documents have been issued yet for any operable unit, meaning remedy selection is still ahead for the site as a whole.
EPA tracking shows that human exposure status is marked as insufficient data, and the contaminated groundwater plume has not been stabilized. Physical construction of the full cleanup is not yet complete. Two businesses currently operate at the site, employing 10 people.
Community members can review fact sheets dating back to 2016 and engage through EPA's community involvement process. A Community Involvement Plan updated in October 2025 outlines how EPA will keep residents informed as conditions change. Documents are available at the Hockessin Public Library at 1023 Valley Road, and at the EPA Region 3 office in Philadelphia, both by appointment. For questions, residents can contact the EPA staff assigned to the site.
