Weldon Spring Ordnance Works (WSOW) was a U.S. Government-owned, contractor-operated (GOCO) facility in St. Charles County, Missouri, 55 km west of St. Louis. The site was originally operated by the Atlas Powder Company during World War II from 1941 to 1945 to produce explosives. The Atomic Energy Commission acquired part of the property in 1955, and Mallinckrodt, Inc. processed uranium ore from 1957 to 1966 under contract. The site has been divided into several parcels, and ownership has transferred over the years. Two portions of the original WSOW property are now Superfund sites that require substantial cleanup efforts. The environmental remediation of the WSOW site is currently designated as a major project of the Defense Environmental Restoration Program of the United States Department of Defense. Part of the original property is still used by the Army Reserve as the Weldon Spring Training Area. Weldon Spring Ordnance Works The site was purchased in 1940, totaling of largely rural land. The towns of Hamburg, Howell, and Toonerville and around 700 citizens of the area were displaced beginning in 1940 and ending the following year. From 1941 to 1945, the Atlas Powder Company manufactured trinitrotoluene (TNT) and dinitrotoluene (DNT) at the site. Four TNT and two DNT production lines were situated on what was to be the Chemical Plant. These operations resulted in nitroaromatic contamination of soil, sediments, and some off-site springs. After World War II, over were transferred to the State of Missouri, including the August A. Busch Memorial Conservation Area. Additional land was transferred to the University of Missouri, St. Charles County, and the Francis Howell School District. Much of the land that was transferred to the University of Missouri has become the Weldon Spring Conservation Area. Weldon Spring Chemical Plant Following a considerable amount of environmental remediation of the facility by the U.S. Army and the Atlas Powder Company, of the former ordnance works were transferred to the United States Atomic Energy Commission (AEC) in 1955 for construction of the Weldon Spring Uranium Feed Materials Plant, now referred to as the Weldon Spring Chemical Plant. Mallinckrodt, Inc. operated the plant from 1957 to 1966 under a contract with the AEC. An additional were transferred to the AEC in 1964. The plant converted processed uranium ore concentrates to uranium tetrafluoride, uranium trioxide, intermediate compounds, and uranium metal. A small amount of thorium was also processed. Wastes generated during these operations were