This site sits in St. Louis County, Missouri, and covers two main areas: the St. Louis Downtown site at the former Mallinckrodt Chemical Plant and the North County sites near Lambert International Airport. From 1942 to 1957, uranium ores were processed at the downtown location. Residues spread to the airport-area sites and contaminated many private and municipal properties, including roughly 78 vicinity properties along Coldwater Creek. The EPA placed the site on the National Priorities List in October 1989.
Contamination affects soil and sediment. Metal contaminants include antimony, arsenic, barium, cadmium, chromium, molybdenum, nickel, selenium, thallium, uranium, and vanadium. Radioactive contaminants include radium-226, thorium-230, thorium-232, uranium-235, and uranium-238. Radium-226, thorium-230, and uranium-238 extend into sediment as well as soil. People can be exposed through ingestion or inhalation of contaminated soil particles, inhalation of radon, and exposure to gamma radiation. Cleanup is expected to reduce cancer risk from one additional case in 10,000 people down to one in 1,000,000.
The U.S. Army Corps of Engineers leads cleanup under two Records of Decision. As of October 2025, crews have removed 317,695 cubic yards of contaminated soil from the St. Louis Airport vicinity properties and collected 41,456 total samples. Source areas at St. Louis Airport and the Hazelwood/Futura area were completed in 2007 and 2013 respectively. Coldwater Creek sampling is nearly complete along its 14-mile length. A major flood in July 2022 did not push contamination above cleanup criteria in the floodplain. The 2022 creek water and sediment samples all tested below remediation goals. Physical construction is not yet complete, and the site has not been deleted from the National Priorities List. The EPA has deferred protectiveness determinations pending further review of institutional controls, inaccessible soils, vapor intrusion, and groundwater data. Human exposure is currently assessed as under control, but groundwater migration has insufficient data at this time.
The site supports active economic use. As of December 2024, 73 on-site businesses employed 6,947 people and generated about $3.2 billion in annual sales. The concrete floodwall and earthen levee protect the St. Louis area from Mississippi River flooding.
Community members can stay involved through several channels. The Corps holds four public meetings per year, including two in-person open houses and two virtual Citizens Outreach Meetings, plus regular email newsletters. A Community Advisory Group (CAG) meets monthly at Black Jack Fire Protection District Station 3 in Florissant. Two no-cost assistance programs are available: the Technical Assistance Services for Communities (TASC) program provides technical experts, and Technical Assistance Grants (TAGs) offer up to $50,000 for community groups to hire their own technical advisor. Contact the EPA's Community Involvement Coordinator for more information.
