There are four Kerr-McGee Superfund sites in the West Chicago area that were contaminated by radioactive thorium waste material. The waste was generated by a processing facility (now closed and owned by the Kerr-McGee Chemical Corporation) that operated in West Chicago between 1932 and 1973. Over many years, thorium-contaminated soil particles from the Kerr-McGee facility entered a nearby storm sewer, contaminating sediments in Kress Creek and the West Branch of the DuPage River. The thorium was also deposited into the floodplain during high water periods. The source of the pollution has been controlled so no more thorium is entering the environment.
An NRDA settlement was agreed upon by the responsible party and the Trustees (federal and state). The matter was settled in 2005. Illinois Natural Resource Trustees are coordinating with the Federal Trustees as the Federal Trustees take the lead on the restoration planning and implementation.