| FOR IMMEDIATE RELEASE Contact: R3press@epa.gov EPA Proposes Removing Portion of Tybouts Corner Landfill
from List of Nation's Most Contaminated Sites EPA seeks comments on proposal to remove portion of site from EPA's National Priorities List PHILADELPHIA (April 4, 2022) – The U.S. Environmental Protection Agency announced today that it has proposed deleting a portion of the Tybouts Corner Landfill in New Castle, Delaware, from the Superfund National Priorities List (NPL). The NPL is a list of the nation's most contaminated hazardous waste sites. EPA deletes sites or parts of sites from the NPL when no further cleanup is required to protect human health or the environment. Years, and sometimes decades, of complex investigation and cleanup work have gone into getting these sites to the point where they can be deleted from the NPL. "Deleting sites from the NPL is a major milestone for Superfund impacted communities," said EPA Mid-Atlantic Regional Administrator Adam Ortiz. "An NPL deletion, and even a portion of a site, signals that cleanup is complete and the site no longer poses a threat to public health and the environment." Thousands of contaminated sites, from landfills, processing plants, to manufacturing facilities exist nationally due to hazardous waste being dumped, left out in the open, or otherwise improperly managed. President Biden's Bipartisan Infrastructure Law will accelerate EPA's work to help communities clean up these contaminated sites with a $3.5 billion investment in the Superfund Remedial Program and reinstates the Superfund chemical excise taxes, making it one of the largest investments in American history to address legacy pollution. This historic investment strengthens EPA's ability to tackle threats to human health and the environment, and EPA has already set action in motion to clear the backlog of the 49 contaminated sites which had been awaiting funding to start remedial action. The Tybouts Corner Landfill Site is in New Castle County, Delaware, approximately 10 miles south of Wilmington and four miles west of the Delaware River. The site was used by the New Castle County Department of Public Works as a municipal sanitary landfill which accepted industrial wastes from December 1968 until July 1971. The landfill consisted of two non-adjoined sections, a West Landfill that was about four acres in size and the Main Landfill that was about 47 acres, with waste ranging from five to 40 feet thick. Contamination was found in two nearby wells in 1976 and again in 1983. The site is being addressed through federal and Potentially Responsible Party (PRP) actions. Based on cleanup activities, soil and groundwater monitoring data and no existing waste remaining on site, EPA has determined that actions are complete for the two parcels on Tybouts Corner Landfill and have been proposed for partial deletion from the NPL. EPA issued a Record of Decision (ROD) and three subsequent Explanations of Significant Differences (ESDs), 1992 ESD, 2000 ESD and the 2021 Explanation of Significant Differences that documents land and groundwater use restrictions for the site. EPA also negotiated several Consent Decrees with numerous companies to perform the remedial design and remedial action. The remedy included: - Material in the West Landfill was excavated and consolidated with the waste in the Main Landfill.
- A groundwater pumping system consisting of eight extraction wells was installed to contain contaminated groundwater at the landfill.
- A subsurface slurry wall, a subsurface barrier that impedes or stops groundwater flow, was installed to prevent clean groundwater from entering the landfill.
- A multi-layer cap was constructed to prevent rain from entering the waste material in the landfill.
- A (passive) venting system was installed to prevent the build-up of landfill gases within the landfill, which uses existing variations in landfill pressure and gas concentrations to vent landfill gas into the atmosphere.
In 1996, a temporary active gas venting system was installed in the Main Landfill portion of the Site due to detection of landfill gas outside the boundaries of the landfill. In 2000, a permanent active gas venting system was installed. The active gas venting system is designed with vacuums or pumps to move gas out of the landfill and is effective in preventing the migration of underground landfill gas beyond the landfill property boundary. Annual monitoring of the passive landfill gas vents continues. In May 2007, contaminant concentrations in groundwater decreased significantly and EPA and the Delaware Department of Natural Resources and Environmental Control (DNREC) agreed to shut down the pumping wells. In 2008, quarterly monitoring of the groundwater ceased, and the wells are now sampled semi-annually. A Groundwater Management Zone established by the State of Delaware that restricts groundwater use will remain in place for the Main Landfill portion of the site until determined unnecessary. While significant progress has been made in the clean-up of the Main Landfill portion of the Tybouts Corner site, all performance standards have not yet been achieved and it will remain on the NPL. EPA published a Federal Register Notice on March 31 proposing to delete all or part of 10 sites from the NPL. There will be a public comment period through May 2. The agency plans to publish another notice with additional final and proposed deletions this fall. | 
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