Army Creek Landfill

Overview

Army Creek Landfill is a former sand and gravel quarry in New Castle County, Delaware, that accepted municipal and industrial waste from 1960 to 1968. EPA added it to the Superfund National Priorities List in September 1983 after groundwater contamination was discovered. Today the site has been redeveloped into a wildlife area, but cleanup work continues because contaminated groundwater has not yet been fully stabilized.

The site holds 18 confirmed contaminants of concern found in groundwater, surface water, sediment, and fish tissue. These include volatile organic compounds such as benzene and 1,2-dichloroethane, metals including arsenic, cadmium, chromium, lead, mercury, nickel, and zinc, and other hazardous substances like benzo[a]pyrene. Per- and polyfluoroalkyl substances (PFAS) have also been detected in gas vents and groundwater samples from the western lobe. The main health risks come from ingesting or touching contaminated soil and groundwater. Two contaminants, BCEE (bis(2-chloroethyl)ether) and 1,4-dioxane, have migrated to Artesian's Llangollen Wellfield, which serves about 5,000 residential customers roughly half a mile away. Artesian has added treatment systems to remove those two chemicals from that water supply.

Eighteen companies and New Castle County agreed to carry out the cleanup under EPA oversight. Work included installing groundwater recovery wells, placing a multi-layer cap over the 50-acre landfill in 1993, and removing more than 100 buried drums filled with volatile and semi-volatile organic compounds found during cap construction. An on-site water treatment facility ran from 1993 to 2004, treating hundreds of thousands of gallons of contaminated groundwater per day. Land and groundwater use restrictions were added in 2020 to protect the cap and prevent exposure to contaminated materials. Groundwater recovery operations shifted to the adjacent Delaware Sand and Gravel Landfill site in 2004 and continue there.

EPA's most recent five-year review, completed September 4, 2024, found the remedy protective of human health and the environment in the short term but included recommendations for long-term protectiveness. Human exposure is currently considered under control, but groundwater migration is not yet stabilized and monitoring continues. Groundwater is sampled semi-annually, and Army Creek surface water and sediment are checked every five years. A supplemental groundwater investigation started in October 2017, with a feasibility study estimated between July and September 2026. The next five-year review is scheduled for 2029.

Community members can engage through EPA's Community Involvement Program. Fact sheets from September 2019 and August 2022 provide updates on site progress. Detailed records are available at the Delaware Department of Natural Resources and Environmental Control in New Castle and at the EPA Region 3 office in Philadelphia, both by appointment. The Community Involvement Coordinator and Remedial Project Manager can answer questions directly.