Mid-Atlantic Superfund

EPA Region 3 (Mid-Atlantic)

Delaware
New Castle County
2 miles southwest of City of New Castle

EPA ID# DED980494496

1st Congressional District

Last Update: April 2009

Other Names

Llangollen Landfill

Current Site Status

The U.S. Environmental Protection Agency has overseen all cleanup construction activities for this site. A multi-layer cap over the 50-acre landfill was completed in 1993. The on-site water treatment system was also completed in 1993. The groundwater recovery system will operate until the groundwater cleanup standards are met.

Site Description

The Army Creek Landfill, located in New Castle County, Delaware, is an abandoned sand and gravel quarry that was operated by New Castle County ("County") from 1960 through 1968 for the disposal of 1.9 million cubic yards of municipal and industrial waste. In 1971, groundwater contamination was discovered in a residential well located in the adjacent Llangollen Estates housing development. Subsequent investigation of the underlying Upper Potomac aquifer identified a plume of organic (e.g., benzene, bis(2-chloroethyl)-ether, 1,2-dichloroethane and methylene chloride) and inorganic (iron and manganese) chemicals migrating from the landfill. The Artesian Water Company (“Artesian”) maintains a public drinking water supply well field one-half mile down gradient of the site, serving approximately 5,000 residential customers.

The site is bordered to the south and east by Army Creek, which discharges into the Delaware River one mile to the east. Another National Priorities List ("NPL") site, the Delaware Sand & Gravel Landfill, is located immediately across Army Creek to the east of the site.

Site Responsibility

Cleanup of this site was the responsibility of the federal government and parties potentially responsible for site contamination.

NPL Listing History

This site was proposed to the National Priorities List of the most serious uncontrolled or abandoned hazardous waste sites requiring long term remedial action on December 30, 1982. The site was formally added to the list September 8, 1983, making it eligible for federal cleanup funds.

Threats and Contaminants

Organic compounds (e.g., benzene, 1,2-dichloroethane, and bis(2-chloroethyl)ether (BCEE)) and inorganic chemicals (e.g., iron and manganese) are currently found in groundwater underlying and down gradient of the Army Creek Landfill and Delaware Sand & Gravel Landfill sites. Groundwater recovery wells were installed and operated in order to prevent contaminants from the sites from reaching public water supply wells.

Contaminant descriptions and risk factors are available from the Agency for Toxic Substances and Disease Registry, an arm of the CDC.

Cleanup Progress

Construction Completed. To minimize the immediate threat, New Castle County installed a series of groundwater recovery wells between the landfills and the public water supply wells. During the 1970's and 1980's, groundwater was pumped from these wells and discharged directly into Army Creek. The final cleanup decision was issued by EPA in June 1990. In September 1990, 18 potentially responsible parties (PRPs), including BP America, Chrysler, Du Pont, General Motors, ICI Americas, Hercules, New Castle County and Waste Management, entered into a mixed-funding Consent Decree whereby the PRPs agreed to implement the final remedy. Construction of a multi-layer cap over the 60-acre landfill began in 1992 and was completed in 1993. During cap construction several “nests” of buried drums, totaling approximately 100 and containing volatile and semi-volatile organic compounds, were discovered, removed and transported to Resource Conservation and Recovery Act (RCRA)-permitted treatment, storage and disposal facilities. Construction of an on-site water treatment facility began in 1992 and was completed in 1994. The groundwater extraction system was designed to capture a comingled contaminant plume migrating from both the Army Creek and Delaware Sand & Gravel NPL sites. The water treatment facility was designed to remove iron, which is harmful to stream life, from extracted groundwater prior to its discharge to Army Creek. In 2004, groundwater recovery operations were shifted to the Delaware Sand & Gravel site where the highest concentrations of BCEE and benzene are found. The groundwater recovered from that site is discharged to the County's wastewater treatment plant located in Wilmington.

Contacts

Site Contacts

Administrative Record Locations