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New Castle Spill
EPA Region 3 (Mid-Atlantic)
EPA ID# DED058980442
1st Congressional District
Last Update: May 2004
Current Site Status
The U.S. Environmental Protection Agency deleted this site from the National Priorities List (NPL) on June 12, 1996. After an investigation of the extent of contamination, the Delaware Department of Natural Resources and Environmental Control (DNREC), with EPA concurrence, determined that no one in the area was using the shallow aquifer for a drinking water supply, so it was appropriate to allow the contaminant, tris-chloropropyl phosphate (TRIS) to reduce in concentration through natural attenuation (exposure to the effects of time and weather). Soil contamination was determined not to pose a significant threat to human health or to the environment.
After the deletion, the Witco Corporation transferred ownership of the site to the City of New Castle. The City has since renovated the historic trolley barn located on the site. The trolley barn is now the home of the New Castle Public Works Department.
Site DescriptionThe New Castle Spill Site, located in New Castle County, Delaware, is a six acre site used for many years by the Witco Chemical Company (Witco) to process materials used in the production of plastic foam.. The site is no longer active. Witco stored drums containing pre-polymer feedstocks and spent solvents on the southern boundary of the property adjacent to the New Castle Board of Water and Light (NCBW&L) property. In 1977, employees of NCBW&L noticed dead grass near the drum storage area, apparently the result of chemical spills on the Witco property. DNREC then directed the NCBW&L to pump the shallow contaminated aquifer and to discharge the water to the nearby wetlands. TRIS, a flame retardant that can be related back to Witco's activities, was detected in soils near the drum storage area and in the shallow ground water beneath the site. VOCs, polychlorinated biphenyls (PCBs), creosote, and phthalates from plastics production were also found in onsite soils. The area surrounding the site is industrial and residential. Approximately 5,500 people live within 3 miles of the site. The shallow aquifer used by the NCBW&L to provide a public water supply, was taken out of service in 1978. Approximately 7,000 people are now served by another source for their potable water supply.
- Site Responsibility
- This site was the responsibility of federal and state governments, the site owner 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, 1996, making it eligible for federal cleanup funds.
Threats and ContaminantsTRIS, a flame retardant that can be related back to Witco's activities, was detected in soils near the drum storage area and in the groundwater beneath the site. VOCs, PCBs, creosote, and phthalates from plastics production were also found in on-site soils. However, soil contamination was determined not to pose a significant threat to human health or to the environment. Drinking contaminated groundwater from the aquifer could have posed a health threat; however, the NCBW&L provided a new water supply to residents found to be at risk. Wetlands adjacent to the site have not been adversely impacted by TRIS contamination. TCE was also found in the groundwater, but was determined to be from an off-site source. The TCE contamination was investigated further by the State. TCE concentrations have since been found to be within safe drinking water standards.
Contaminant descriptions and risk factors are available from the Agency for Toxic Substances and Disease Registry, an arm of the CDC.
In 1989, after an investigation of the extent of contamination at the site, the DNREC, with EPA concurrence, determined that, because no one in the area was using the shallow aquifer for a drinking water supply, it was appropriate to allow the TRIS to reduce in concentration through natural attenuation. DNREC estimated it would take four years for the TRIS concentrations to reach safe levels. Soil contamination was determined not to pose a significant threat to human health or to the environment. As a safeguard, DNREC and EPA required the following actions in a 1989 Record of Decision: (1) quarterly monitoring of the shallow groundwater to ensure natural attenuation was effective; (2) annual monitoring of the deeper groundwater aquifer to make sure TRIS had not migrated down from the shallow aquifer; (3) annual monitoring of surface water and sediments in the adjacent wetlands; and, (4) restrictions which prevented anyone from installing wells in the vicinity of the site.
Pursuant to the April 1991 Consent Decree with EPA requiring Witco to implement the remedy, Witco conducted quarterly groundwater, surface water and sediment monitoring from 1992 through September 1995. In January 1996, EPA determined that the data showed that TRIS levels in the shallow aquifer had reached the established safe levels by natural attenuation. Thus, the cleanup was complete and quarterly monitoring was discontinued. DNREC established the institutional controls required by the selected remedy by restricting the installation of wells in the shallow aquifer within one-half mile of the site. After the cleanup was complete, DNREC removed the ground water restriction and EPA deleted the site from the NPL on June 12, 1996.