The Seaway Site, located in Tonawanda, New York, was operated as a landfill from 1930 to 1993, accepting a variety of municipal, commercial, construction, and industrial wastes. Nearby, in the 1940s, the former Linde Air Products Division of Union Carbide processed uranium ores under contract to the Manhattan Engineer District (MED). The mill tailings from the FUSRAP-related activities were transported from the Linde Site to the former Haist Property, now known as the Ashland 1 Site. During the mid-1970's, Ashland Oil constructed oil tanks on the Ashland 1 property. During the construction, materials containing radioactive residues were removed from the area and transported by Ashland Oil to the Seaway landfill and what was the Ashland 2 Site and used as cover or grading material. This material was also placed in what is now known as Seaway Areas A, B and C.
During the Corps' remediation efforts at Ashland 1, FUSRAP-related materials at elevated concentrations were found that appear to extend onto the Seaway Site. At one location, elevated concentrations appear to extend under the capped portion of the landfill. Remediation of this material as part of the Ashland 1 remediation ceased at the site boundary. This area is referred to as Seaway Southside. There is also an area on the north side of Seaway near Area A where, during Ashland 2 Site remediation efforts, elevated concentrations of FUSRAP-related materials were found outside of the Seaway containment system (i.e., outside the area encompassed by the landfill's leachate collection system). This area is referred to as Seaway Northside. Both Seaway Southside and Seaway Northside are now included within the scope of the FUSRAP remediation activities for the Seaway Site.