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The Weldon Spring Quarry/Plant/Pits site is in St. Charles County, Missouri, approximately 30 miles west of St. Louis. The Department of Energy (DOE) is the lead agency for the site. The site encompasses two geographically distinct properties—the Weldon Spring Chemical Plant and Raffinate Pits (Chemical Plant) and the Weldon Spring Quarry (Quarry). In 1940, the U.S. government acquired 17,232 acres of rural land in St. Charles County to construct the Weldon Spring Ordnance Works. In 1941, the Army began production of trinitrotoluene and dinitrotoluene to support World War II efforts. The Ordnance Works was decommissioned in 1945 following the end of the war. In 1956, the Army transferred 205 acres of the property to the U.S. Atomic Energy Commission (AEC) for construction of the Weldon Spring Uranium Feed Materials Plant, now referred to as the chemical plant. The chemical plant converted processed uranium ore concentrates to pure uranium trioxide, intermediate compounds, and uranium metal. A small amount of thorium was also processed at the chemical plant. An additional 14.88 acres, including the Quarry, were transferred from the Army to AEC. The Quarry was mined for limestone aggregate used in construction of the Weldon Spring Ordnance Works. The Quarry was also used by the Army for burning wastes from explosives manufacturing and disposal of explosive-contaminated rubble during operation of the Weldon Spring Ordnance Works. In 1960, the Army transferred the Quarry to AEC, who used it from 1963 to 1969 as a disposal area for uranium and thorium residues from the chemical plant.

Historical operations at the site, by both the DOE and the Army, resulted in the release of hazardous substances, primarily nitroaromatic and radiological compounds, to soil, sediment, surface water, and groundwater at the site. The site was listed on the National Priority List on July 30, 1987, and a Federal Facility Agreement became effective in 1986. The site was subsequently divided into four Operable Units (OUs)—the Chemical Plant OU, the Groundwater OU, the Quarry Bulk Waste OU, and the Quarry Residuals OU. The Weldon Spring Quarry/Plant/Pits site is surrounded by the Weldon Spring Ordnance Works site, a separate National Priority List site. The Army is the lead agency for the Weldon Spring Ordnance Works site.



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What Has Been Done to Clean Up the Site?

Remedial activities at the Chemical Plant and the Quarry have been completed with the exception of long-term groundwater monitoring at both locations. The site reached construction completion in August 2005, and the long-term surveillance and maintenance activities have become the main focus of the project.

The site received the EPA Superfund Sitewide Ready for Anticipated Use (SWRAU) designation from the U.S. Environmental Protection Agency in a letter dated March 20, 2013. The SWRAU performance measure reports sites documented as ready for reuse when the entire construction-completed NPL site meets the following requirements:

All cleanup goals in the Record of Decisions (RODs) or other remedy decision documents have been achieved for media that may affect current and reasonably anticipated future land uses of the site, so that there are no unacceptable risks.

All institutional or other controls required in the RODs or other remedy decision documents have been put in place.

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What Is the Current Site Status?

The DOE continues to perform periodic groundwater monitoring at the Chemical Plant and Quarry areas. In addition, annual inspections are conducted to ensure Land Use Controls remain in place and effective.

The next Five-Year Review is scheduled to begin in 2020 and be completed by September 2021. The purpose of the Five-Year Review is to evaluate the implementation and performance of site remedies in order to determine if they are or will be protective of human health and the environment. Five-Year Reviews are required for any remedy that results in any hazardous substance, pollutant, or contaminant remaining at the site above levels that allow for unlimited use and unrestricted exposure.














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Activity and Use Limitations

At this site, activity and use limitations that EPA calls institutional controls are in place. Institutional controls play an important role in site remedies because they reduce exposure to contamination by limiting land or resource use. They also guide human behavior. For instance, zoning restrictions prevent land uses – such as residential uses – that are not consistent with the level of cleanup.

For more background, see Institutional Controls.


Covenants have been negotiated and finalized with surrounding state agency landowners for implementing required use restrictions. The state agencies included Missouri Department of Conservation, and Missouri Department of Transportation/St. Charles County. The covenants are in place to restrict potential use of contaminated groundwater and to restrict land use in the Southeast Drainage area and at the Quarry site. These areas are visually inspected annually to ensure the Land Use Controls and Institutional Controls remain in place and are effective.

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Sampling and Monitoring

The DOE conducts sampling and monitoring in accordance with the approved Long-Term Surveillance and Maintenance Plan. Results are reported to the EPA and Missouri Department of Natural Resources in annual reports.

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