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Halby Chemical Superfund Site

Date Posted: August 14, 2003

The trustees, U.S. Fish and Wildlife Service (FWS), National Oceanic and Atmospheric Administration (NOAA), and the State of Delaware, together with the Responsible Parties (RPs), Crompton Corporation and the Pyrities Company, have entered into an agreement to purchase a 248-acre tidal wetlands area known as the Cleaver Marsh in exchange for a Covenant Not To Sue (CNTS) for release from natural resource damage (NRD) liability. The Halby Chemical Superfund Site is a 14-acre site located in the highly industrialized area of Wilmington, New Castle County, Delaware. Thiocyanates, sulfides, hydrosulfides, and thioglycolates were produced at the former process plant. Between 1948 and 1964, Halby Chemical discharged all wastes directly into an unlined lagoon which then flowed into a wetlands via a drainage ditch. Due to the extent of the contamination and the need to prevent further impacts to ground water, the U.S. Environmental Protection Agency (EPA) filled in the wetlands and capped the area with asphalt. This agreement addresses the natural resource damages (NRD) associated with the 7.2 acres of wetlands lost as part of the Site remediation.

A Habitat Equivalency Analysis (HEA) was performed by the trustees to calculate injury to natural resources and quantify restoration needed to replace the services lost. Through the HEA, it was determined that the restoration project would have to include between 39 and 121 acres. This project also includes and fully credits the RPs for the acreage which the EPA requires for mitigation purposes, estimated to be 21.6 acres. Therefore, the total acreage needed to satisfy both mitigation and NRD requirements is between 60.6 and 142.6 acres. The Cleaver Marsh project includes 248 acres located 14 miles south of the Halby Site and consists of habitat degraded by Phragmites. Plans are to enhance this habitat through Phragmites control and the addition of two osprey nesting structures. Ownership of the property will be transferred to DNREC and added to two adjacent State wildlife areas.

Sherry Krest at 410-573-4525

U.S. EPA, Mid-Atlantic Hazardous Site Cleanup -

Delaware Department of Natural Resources and Environmental Control -

Last updated: June 12, 2015