Remediation Status: Site closed

Why the technology was selected:
Since the site was on a fast track for redevelopment, the remediation of the site had to be completed within 3 months. Based on this and the results of the site assessment, the consultant proposed to remediate the site by excavating and disposing the soils with high concentrations of PCE and treating the groundwater in the excavation with sodium permanganate (NaMnO4). In addition, NaMnO4, would be injected down gradient of the excavation to treat any extended plume and to provide a barrier against further migration.

Date implemented:
January 6, 2005

Final remediation design:
The initial action was to remove and stockpile the overburden material (0-10 ft bgs), which would later be used as backfill. At a depth of approximately 10 ft. bgs the zone of contamination was encountered. The excavation continued to depth of approximately 25 ft. bgs. No groundwater was present in the excavation upon completion, although the bottom of the pit was below groundwater levels measured and present in the surrounding monitoring wells. A garden sprayer was utilized to apply about 45.6 pounds of NaMnO4 to the bottom of the excavation and the walls below 10 ft. bgs. Large rock (6 to 8-inch in diameter) was then utilized to fill the first 6-feet of the excavation. This rock was used not only to stabilize the fill, but to allow groundwater, if any, to mix with the NaMnO4 for treatment. Clean overburden material was mixed with 1-inch minus rock and utilized to fill the excavation from 19 to 8 ft. bgs. The remainder of the overburden material was used to fill the excavation from 8ft. bgs. to the surface. While the backfill operation was being conducted, a Geoprobe® rig was used to inject NaMnO4 in four borings down gradient of the excavation. Approximately 6 pounds of NaMnO4 was injected in each of the borings in an interval from 10 to 24 ft. bgs.

Results to date:
Approximately 857 tons of the impacted soil were disposed of as special waste and the remaining 300 tons of impacted soil were disposed of as hazardous waste. Subsequent sampling of the groundwater over a 3 month period indicated that the PCE concentrations dropped from an initial level of 17 mg/L to 8.4 mg/L and remained stable. The treatment of the groundwater reduced the contaminants to levels safe for indoor air protection for any use of the site. Because the treatment did not remediate the site to levels considered safe for use of the groundwater as a water supply, an Activity and Use Limitation (AUL) prohibiting the use of the groundwater was required. The AUL was recorded with the St. Charles County Recorder of Deeds for the purposes of protecting public health. A Certification of Completion Letter for the site was issued by the Brownfields/Voluntary Cleanup Program (BVCP) on August 11, 2005.

Why the technology was selected:
Since the site was on a fast track for redevelopment, the remediation of the site had to be completed within 3 months. Based on this and the results of the site assessment, the consultant proposed to remediate the site by excavating and disposing the soils with high concentrations of PCE and treating the groundwater in the excavation with sodium permanganate (NaMnO4). In addition, NaMnO4, would be injected down gradient of the excavation to treat any extended plume and to provide a barrier against further migration.

Date implemented:
January 6, 2005

Final remediation design:
The initial action was to remove and stockpile the overburden material (0-10 ft bgs), which would later be used as backfill. At a depth of approximately 10 ft. bgs the zone of contamination was encountered. The excavation continued to depth of approximately 25 ft. bgs. No groundwater was present in the excavation upon completion, although the bottom of the pit was below groundwater levels measured and present in the surrounding monitoring wells. A garden sprayer was utilized to apply about 45.6 pounds of NaMnO4 to the bottom of the excavation and the walls below 10 ft. bgs. Large rock (6 to 8-inch in diameter) was then utilized to fill the first 6-feet of the excavation. This rock was used not only to stabilize the fill, but to allow groundwater, if any, to mix with the NaMnO4 for treatment. Clean overburden material was mixed with 1-inch minus rock and utilized to fill the excavation from 19 to 8 ft. bgs. The remainder of the overburden material was used to fill the excavation from 8ft. bgs. to the surface. While the backfill operation was being conducted, a Geoprobe® rig was used to inject NaMnO4 in four borings down gradient of the excavation. Approximately 6 pounds of NaMnO4 was injected in each of the borings in an interval from 10 to 24 ft. bgs.

Results to date:
Approximately 857 tons of the impacted soil were disposed of as special waste and the remaining 300 tons of impacted soil were disposed of as hazardous waste. Subsequent sampling of the groundwater over a 3 month period indicated that the PCE concentrations dropped from an initial level of 17 mg/L to 8.4 mg/L and remained stable. The treatment of the groundwater reduced the contaminants to levels safe for indoor air protection for any use of the site. Because the treatment did not remediate the site to levels considered safe for use of the groundwater as a water supply, an Activity and Use Limitation (AUL) prohibiting the use of the groundwater was required. The AUL was recorded with the St. Charles County Recorder of Deeds for the purposes of protecting public health. A Certification of Completion Letter for the site was issued by the Brownfields/Voluntary Cleanup Program (BVCP) on August 11, 2005.