Superfund Information Systems: Site Profile

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The Weldon Spring Site is located in St. Charles County, Missouri, about 30 miles west of St. Louis. The site comprises two geographically distinct properties owned by the Department of Energy (DOE): the Weldon Spring Chemical Plant and Raffinate Pit Sites and the Weldon Spring Quarry Site. The Chemical Plant is located about 2 miles southwest of the junction of Missouri State Route 94 and U.S. Highway 40/61. The Quarry is about 4 miles southwest of the Chemical Plant.

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What Is Being Done to Clean Up the Site?

The selected remedy included treatment and disposal of wastes from the plant, raffinate pits and quarry. An engineered disposal cell was constructed on-site to store the treated wastes. The disposal cell was completed in 2001, and on-site construction activities were completed in 2005. Residual contamination is addressed through institutional controls and long-term surveillance and management.

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What Is the Current Site Status?

The selected remedy included disposal of contaminated waste both off-site and in an engineered disposal cell constructed on-site. Post remedial action, contamination remains at the site at the following locations:

- An on-site disposal cell contains approximately 1.48 million cubic yards of contaminated material.

- Residual groundwater contamination remains in the shallow aquifer beneath the chemical plant, at the quarry and at some surrounding areas.

- Several springs near the chemical plant discharge contaminated groundwater.

- Residual soil and sediment contamination remain in the Southeast Drainage.


- Contamination remains at two culvert locations along Missouri State Route 94 and Highway D.


- Residual soil contamination remains at inaccessible locations within the quarry.

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EPA’s Involvement at the Site

In 1955, after the Army demolished and removed the works, the Atomic Energy Commission (AEC) started construction of the Weldon Spring Feed Materials Plant on the land. The Army disposed of soil and building rubble from the demolition, which were contaminated with trinitrotoluene (TNT) and dinitrotoluene (DNT), in the deepest part of the quarry. DOE, successor to AEC, now owns the plant.

In 1957, the Weldon Spring Feed Materials Plant began converting uranium concentrates to pure uranium salts and metal. The plant also processed some thorium ore concentrates. During operations, the buildings, equipment, immediate terrain, process sewer system and drainage easement to the Missouri River became contaminated with uranium, thorium and their decay products. During 1959 to 1969, AEC used the quarry for disposal of drums, process equipment, building rubble and soils contaminated with thorium, uranium and their decay products. Also, radioactive process wastes were disposed of near the plant in four raffinate pits covering about 50 acres.

DOE found elevated levels of uranium, radium and nitroaromatics in monitoring wells adjacent to the quarry. Following cleanup, operation and maintenance activities and monitoring are ongoing.

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