Standard Chlorine of Delaware, Inc.

Overview

Standard Chlorine of Delaware, Inc. operated near Delaware City, Delaware, from 1966 to 2002, manufacturing chlorinated benzene compounds. A spill in 1981 and a much larger one in 1986, which released 569,000 gallons of volatile organic compounds (VOCs), contaminated groundwater, soil, creek sediments, surface water, and nearby wetlands. EPA added the site to the Superfund National Priorities List (NPL) in July 1987. After the owner declared bankruptcy and abandoned the plant in 2002, EPA and the Delaware Department of Natural Resources and Environmental Control (DNREC) took over cleanup.

Contaminants at the site include chlorinated compounds such as dichlorobenzenes, trichlorobenzenes, and tetrachlorobenzenes, along with VOCs like benzene, toluene, trichloroethene, and tetrachloroethene. Heavy metals including arsenic, cadmium, chromium, lead, and mercury have been found in soil and groundwater. Polychlorinated biphenyls (PCBs), dioxins, pesticides such as aldrin and chlordane, and petroleum-related compounds are also present. These contaminants appear across groundwater, soil, sediment, and surface water.

EPA removed millions of pounds of abandoned chemicals between 2002 and 2006. A pump-and-treat system with a subsurface barrier wall has operated as an interim groundwater remedy since 2007. In May 2024, EPA selected a final groundwater remedy that continues this approach and adds institutional controls to prevent consumption of contaminated groundwater. A contractor is currently being hired to design that final system. A protective cap with native vegetation and a soil gas collection system was completed over the former plant area in spring 2017. Cleanup design for soils, sediments, and wetlands along Red Lion Creek is underway, with construction expected to start in 2027. A fish consumption advisory remains in effect for Red Lion Creek due to PCBs and dioxin.

EPA assessments indicate that human exposure is currently under control across the entire site, with no unacceptable human exposure pathways at this time. However, groundwater migration is not yet stabilized and physical construction of cleanup work is not complete. Zoning restrictions and a Groundwater Management Zone enforced by DNREC prohibit uses incompatible with current cleanup levels and bar consumption of contaminated groundwater. EPA conducted its most recent five-year review in June 2021, with the next review estimated for mid to late 2026.

Community members can stay informed through fact sheets and updates on EPA's website, including documents dating back to 2002. A public meeting will be held before wetland construction begins in 2027. Records are available at the Delaware City Public Library at 250 Fifth Street, Delaware City, and at EPA Region 3 in Philadelphia. Residents with questions can contact EPA's Community Involvement Coordinator or Remedial Project Manager.