Tybouts Corner Landfill, also called New Castle County Landfill, is a 51-acre former municipal and industrial waste site in New Castle County, Delaware. It operated from December 1968 to July 1971 and was added to the Superfund National Priorities List (NPL) in 1983 after contamination was found in nearby drinking water wells in 1976 and 1983. EPA installed a public water line in 1985 to serve homes near the site whose wells were affected.
EPA identified nine contaminants of concern in groundwater at the site. These include benzene, vinyl chloride (chloroethene), 1,2-dichloroethane, chloroethane, toluene, xylene, acetone, and other metals and organic compounds. These chemicals posed a risk to local and regional aquifers used for drinking water.
Cleanup work started in earnest in 1995. Workers excavated waste from the west portion of the landfill and moved it to the main landfill area. They installed eight groundwater extraction wells, built a subsurface slurry wall to keep clean groundwater out of the landfill, capped the landfill with multiple layers to block rainwater, and put in gas venting systems. A permanent active gas venting system was added in 2000. By May 2007, groundwater contamination had dropped enough that pumping wells were shut down. Groundwater is now sampled twice a year. Annual air modeling shows gas vent emissions do not pose an unacceptable risk to human health. A five-year review completed in July 2025 is the most recent assessment of the remedy. The 2020 review had confirmed the remedy remained protective. Institutional controls restrict groundwater use and land activities that would conflict with cleanup levels. Native grasses and wildflowers now cover the landfill cap to prevent erosion. In 2014 a developer purchased the site and adjacent parcels, with the site zoned for commercial use and adjacent land zoned for residential development.
On August 18, 2022, two parcels were officially deleted from the NPL after all cleanup goals were met and no waste remained on those parcels. The rest of the site remains on the NPL. EPA has determined that human exposure is under control and contaminated groundwater is stabilized and not spreading.
Community members who want to learn more or get involved can contact EPA's Community Involvement Coordinator, Eric Pollard, by email or phone. Physical 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. Appointments can be scheduled by calling either office directly.
