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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 that are owned by the Department of Energy, or DOE: the Weldon Spring Chemical Plant and Raffinate Pit Sites, or Chemical Plant, and the Weldon Spring Quarry, or Quarry. The former Chemical Plant is located about 2 miles southwest of the junction of Missouri State Route 94 and Interstate 64. The Quarry is about 4 miles southwest of the former Chemical Plant. Both sites are accessible from Missouri State Route 94. The Chemical Plant and Quarry Areas total 228.16 acres. The former Chemical Plant property occupies 219.50 acres; the Quarry occupies 8.66 acres.


Remediation of the Weldon Spring Site was administratively divided into four Operable Units: the Chemical Plant Operable Unit, or CPOU, the Groundwater Operable Unit, or GWOU, the Quarry Bulk Waste Operable Unit, or QBWOU, and the Quarry Residuals Operable Unit, or QROU.

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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, or SWRAU, designation from EPA 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 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?

Five-Year Reviews

Five-year reviews, or FYRs, are conducted at sites to evaluate the protectiveness for remedial actions where hazardous substances, pollutants, or contaminants remain above levels that allow for unlimited use and unrestricted exposure. The fifth and most recent FYR for the site was completed on September 30, 2016. The DOE provided protectiveness statements in FYR report. The EPA concurred with the following protectiveness statements for three of the four OUs:


The remedy that has been implemented at the CPOU is protective of human health and the environment. Contaminant sources are contained in an onsite disposal facility at the Chemical Plant. The environmental monitoring data and annual inspections continue to verify that the disposal cell is functioning as intended. The remedy that has been implemented at the Southeast Drainage is protective of human health and the environment. The remedy consisted of removing contaminated soils and sediment to levels that are protective under the current land use. The drainage has recovered from the removal activities and is stable. ICs are used to maintain appropriate land and resource use and ensure that the remedy remains protective over the long term.


The remedy for the QBWOU is protective of human health and the environment. The action consisted of excavating the bulk wastes from the Quarry and placing them in controlled temporary storage pending final placement in the onsite disposal cell at the Chemical Plant. Excavating the wastes from the Quarry eliminated the potential for direct contact with the waste material and removed the source of ongoing contaminant migration to groundwater.


The remedy for the QROU is protective of human health and the environment through long-term monitoring with ICs. The remedy consists of long-term groundwater monitoring and ICs to maintain appropriate land and resource use and ensure that the remedy remains protective over the long-term.

For the GWOU, the EPA concurred that the remedy is currently protective of human health and environment, but the EPA identified an issue that may potentially affect long-term protectiveness. As a result, the EPA found the remedy at the GWOU to be currently protective of human health and environment and issued the following independent protectiveness statement:


The remedy for the GWOU will be protective of human health and the environment upon attainment of groundwater cleanup goals, through monitored natural attenuation (MNA), which is expected to require approximately 100 years to achieve. The clean-up time for Burgermeister Spring is predicted to be much shorter than the 100 year time frame. In the interim, exposure pathways that could result in unacceptable risks are being controlled and ICs are in place to prevent the groundwater from being used in the restricted area.

The change in the protectiveness statement for the GWOU resulted in a change for the entire site. Therefore, the EPA issued the following independent protectiveness statement for the entire site:


This five-year review found the remedy for the entire site to be currently protective of human health and the environment. However, in order for the remedy to be protective in the long-term, issues will need to be addressed at the GWOU.

The next FYR is due on September 30, 2021.

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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.

The Long-Term Surveillance and Management, or LTS&M, Plan states “DOE will conduct a formal annual inspection of the physical locations addressed by ICs. DOE also will evaluate whether the ICs remain effective in protecting human health and the environment and, in coordination with EPA and MDNR, will take appropriate action if evidence indicates the controls are not effective.”

Easements have been negotiated and finalized with surrounding state agency landowners for implementing use restrictions required on the state properties. The state agencies included MDC, MDNR-Parks, and MoDOT/St. Charles County. The easements are in place to restrict potential use of contaminated groundwater in the hydraulic buffer zone and also to restrict land use in the Southeast Drainage area and at the Quarry site. During the inspection, the final institutional control areas were inspected in accordance with the current information in the LTS&M Plan.

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Sampling and Monitoring

The DOE conducts sampling and monitoring in accordance with the LTS&M Plan. Results are reported to the EPA and MDNR in annual reports.

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