From Investigation to Restoration: Cades Cove Remediation Reaches Major Milestone

More than a decade of sampling, planning, and residential cleanup culminates in restoration of eight North St. Louis County properties.

For years, seven residential properties and one common ground property at Cades Cove, a neighborhood in North St. Louis County, represented one of the most complex types of work facing the U.S. Army Corps of Engineers' Formerly Utilized Sites Remedial Action Program (FUSRAP). The contamination was not beneath an open industrial tract or an isolated work site. It was intertwined with a neighborhood.

By September 2026, crews had removed six houses, excavated contaminated soil, backfilled the properties, and started restoring the ground surface. The physical work marked the culmination of an investigation that stretched across more than a decade and required the project team to move from broad floodplain sampling along Coldwater Creek to targeted investigation beneath and around residential structures.

A cleanup that began with questions The investigative history of Cades Cove dates to 2014, when sampling began in the Coldwater Creek floodplain near the subdivision. The initial phase focused on planned predesign investigation (PDI) locations adjacent to Cades Cove. Those samples were below remediation goals and did not warrant further investigation.

That is, until October 2015, when the investigation changed. During a second phase of hillside sampling, the project team identified the first elevated sample at one of the properties. Five sampling stations from that phase exceeded remediation goals, with contamination found approximately 2.5 to 4 feet below ground surface.

That discovery prompted additional phases designed to bound the contamination and understand how it reached the residential area. By 2016, sampling identified contamination in the backyard of another Cades Cove property at depths approaching 10 feet below ground surface. In 2017, review of earlier data identified contaminated soil zones near the elevation of a historic Coldwater Creek meander scar between two Cades Cove addresses.

Investigators continued to follow the evidence. Additional sampling in 2018 and 2019 examined the historic creek meander, drainage and low-lying areas, and the boundaries of previously identified contamination. Some locations exceeded remediation goals at depths ranging from about 3.5 to more than 12 feet below ground surface.

The investigation expanded again in the years that followed. USACE issued additional PDI reports, revised the project work scope, and conducted another major sampling effort beginning in July 2023. Sampling beneath five basements began in February 2024, in hopes of zeroing in on potential contamination. Geotechnical drilling followed in backyards and additional PDI sampling continued into spring 2025.

Before remediation could begin, rights of entry had to be obtained from each property owner. The contractor, HydroGeoLogic, Inc. (HGL), collected 1,693 samples from 163 boring locations in the Cades Cove area. Each phase narrowed the uncertainty and gave engineers and health physicists a clearer picture of where contamination was and how deep excavation would need to go.

Turning investigation into action Physical remediation began March 9, 2026. Over the next several months, crews excavated approximately 11,750 cubic yards of contaminated soil from seven residential properties and a Cades Cove common ground property behind the homes.

Removing that volume required 1,479 truckloads. Each truck was tarped and inspected for contamination before leaving the remediation area. Health physics technicians surveyed trucks and equipment, and crews decontaminated them when needed. Water served as the primary dust suppression method, while continuous air monitoring, groundwater monitoring, and daily surveys of work areas, haul routes, personnel, and equipment helped the team detect and prevent contamination spread.

The team transported the contaminated material to the St. Louis Airport Site loadout facility, where it was taken to an approved waste disposal facility that specializes in this type of waste. As of Sep. 16, 57 railcars carried approximately 4,735 cubic yards of material away for disposal. The remaining contaminated soil remain stockpiled at the loadout facility for later shipment.

The excavation phase concluded June 28. According to the project team, crews encountered no unexpected conditions, experienced no safety incidents, and avoided significant setbacks, completing their work about a month ahead of schedule. The excavation footprint expanded south into another residential property, but the team had anticipated that possibility in the remedial design and coordinated with the property owner.

”Residential remediation requires us to think beyond excavation. We have to protect workers and neighbors, manage truck traffic and dust, coordinate closely with property owners, verify every area we clean up and then put the property back in a condition that can be used again," said Phil Moser, FUSRAP and environmental chief for the USACE, St. Louis District.

Verifying the cleanup Excavation alone did not establish that the properties were complete. The project required independent contractor verification that the remaining soil met remediation goals established in the Record of Decision, which establishes the cleanup requirements and remediation goals.

The USACE verification contractor followed Multi-Agency Radiation Survey and Site Investigation Manual guidance established in the Final Status Survey Plan. Teams conducted gamma walkover surveys and collected soil samples across all eight properties to verify that the remediated areas meet criteria for unlimited use and unrestricted exposure.

That verification step is central to the closeout process. It converts the physical act of removing soil into a documented determination that cleanup requirements have been achieved.

Putting the neighborhood back together As excavation areas cleared verification, the project shifted from removal to restoration. Between May 28 and Sept. 3, crews placed approximately 3,430 cubic yards of clean fill, taken from the Ft. Belle Quarry in Florissant, and restored the properties to grade.

Surface restoration began at the end of August, and crews have reseeded the properties with perennial rye, annual rye, and Kentucky 31 tall fescue. Crews placed erosion control blankets on sloped areas. Temporary orange construction fencing will remain around restoration areas while the grass establishes.

The restoration plan also includes a watering schedule after seed placement and sidewalk panel replacement. Driveway areas removed during the project are being restored as seeded ground. Aprons will be restored to match the curb, street layout, and applicable surface material rather than being rebuilt as driveway aprons.

The temporary access road behind the subdivision will remain in place until approximately October 2027, as it will continue to support FUSRAP work for future remediation of the creek behind the subdivision. That area is currently anticipated to be remediated from approximately May through September 2027.

A framework for future residential work The approximately $15 million Cades Cove effort matters beyond the eight properties themselves. According to the project team, the work established a framework for residential remediation under the North St. Louis County Sites FUSRAP mission.

Residential work combines technical cleanup requirements with issues that are less prominent at industrial or undeveloped sites. Crews must work around homes, property boundaries, utilities, streets, and neighborhood activity. The project team also has to communicate directly with property owners and nearby residents while preserving access, controlling construction impacts, and documenting the final condition of each property.

Cades Cove effectively tested that full process under demanding conditions. The team moved from investigation and remedial design through structure removal, excavation, transport, radiological controls, verification, and property restoration without a safety incident. No other removal of homes is currently anticipated in the St. Louis FUSRAP scope of work.

"Cades Cove gave the program a repeatable model, should it be needed, for how to execute remediation in a residential setting safely. That experience will help inform future work as USACE continues addressing contamination in North St. Louis County," said Moser.

The work continues Although the primary physical remediation at the eight properties is complete, Cades Cove will not immediately disappear from the program's workload.

Four groundwater monitoring wells remain at the site: three targeting the shallow groundwater aquifer and one targeting the deep aquifer. They will be sampled quarterly for at least one year to meet Record of Decision requirements and verify that remedial action did not negatively affect groundwater quality nearby.

The documentation process will also continue. A revised Remedial Action Summary is projected for completion by Dec. 1, 2026, with the next revision expected by the end of January 2027. Final project documentation is expected to continue through December 2027.

For the neighborhood, however, the most visible change is already underway. Where remediation once required removal of houses, excavation equipment, trucks, and temporary infrastructure, crews graded the soil back to its original grade, replaced sidewalks, and planted grass.

The owners of the six properties where homes were demolished retained ownership throughout the cleanup. Once final project documentation is complete, the properties will be available for unlimited use in accordance with the Record of Decision.

After more than a decade of investigation and planning, these properties have moved from a question about the extent of contamination to a documented cleanup and restoration effort. The milestone closes one chapter for the St. Louis FUSRAP team, while giving USACE a tested approach for the residential work.

FUSRAP identifies, investigates, and cleans up sites contaminated by the nation's early atomic energy program. The U.S. Army Corps of Engineers, St. Louis District, manages FUSRAP work in the St. Louis area.

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