Six Areas of Concern (AOCs) have been investigated by the Corps as part of a site-wide Remedial Investigation to evaluate any residual radiological contamination resulting from MED operations at Chambers Works. The AOCs are former sites of uranium production processes, drainage areas leading from production areas, and potential MED waste disposal areas. Figure 1 shows the location of these areas and brief site descriptions are provided below:
1. AOC 1, Former Building 845 Area (Miscellaneous Stores Bldg.) – The former building was a four-story, 50,000 - square foot steel frame structure located in the northwest quadrant of the Chambers Works site. During MED operations uranium recovery processes were conducted in this building. MED work in Building 845 consisted of the recovery of uranium from scrap and other byproducts. Wastes from these recovery processes were discharged to the wooden trough located east of the building that ultimately discharged to the Central Drainage Ditch (CDD). DOE performed interior surface decontamination of the building in 1996. In 1999 DuPont completed demolition of the building and the Corps disposed of the structural steel containing fixed radiological contamination. Field investigations have confirmed uranium in shallow soils and groundwater beneath the footprint of the former building to a depth of four feet below ground surface. See Description
2. AOC 2, F Parking Corral – Currently the area is a paved parking lot area that was built over the site of former Building 708. During MED operations uranium refinement processes occurred in Building 708. The former building was located in the northeast portion of the parking corral. In 1945, part of Building 708 was demolished and removed from the site. In 1953 the remainder of the building and some underlying soil were removed and disposed of near the Historical Lagoon A. Field investigations have confirmed uranium in shallow soils and groundwater beneath the footprint of the former building.
3. AOC 3, Central Drainage Ditch 16 – The Central Drainage Ditch (CDD) was used to transfer process wastes from production areas to the lagoon complex during the MED operational period. The portion of the CDD that ran in between AOC 1 and AOC 2 was remediated by DuPont in 1997 to address lead contamination in soils as part of a RCRA corrective action. An independent verification study performed for DOE confirmed that the chemical remediation that DuPont conducted removed radiological contamination in soils to sufficiently low levels. Recent field investigations were completed in 2003 and no significant radiological contamination was found. The highest detected uranium concentration was 98 picoCuries/gram (pCi/g), collected from a sediment sample near the former Building 845. No filtered groundwater samples exceeded the maximum contaminant level for uranium. No further action is anticipated. See Description
4. AOC 4, Historical Lagoon A – This is the site of a former wastewater lagoon complex. Lagoon A historically received wastewater from Chambers Works, including MED operational areas. The CDD connected the lagoon with MED production areas. During backfilling activities, MED building debris, rubble, and soil were deposited in some areas, including the North Burial Area. Field investigations have confirmed uranium impact to soils and groundwater. See Description
5. AOC 5, Former Building J-16 – This building was used as a research laboratory conducting batch experiments for uranium refinement during MED operations. The building, used by Jackson Labs, was demolished in the mid 1950s. At that time the foundation and several feet of underlying soil were removed. DuPont then constructed Building J-26 over the footprint of Building J-16. Field investigations were conducted within the footprint of the building and the former drainage ditch that surrounded the building and received waste from it. Investigations were completed in 2003 concluding that no significant radiological contamination existed in this area. MED uranium was not encountered in soil and groundwater samples. See Description
6. AOC 6, East Area – The East Area is a large DuPont production area and was used to manufacture chlorinated solvents and lubricants under contract with MED. The East Area contains a disposal area for demolition debris and discarded equipment from MED production areas and other DuPont processes. This disposal area, designated the East Burial Area, is located adjacent to and north of East Road. Previous radiological surveys of this area have indicated elevated concentrations of uranium. Field investigations in 2004 – 2006 have confirmed limited impact to soils and groundwater. See Description