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Record of Decision System (RODS)



City & State:  CHESTERFIELD COUNTY  VA  23237
EPA ID:  VA3971520751
EPA Region:  03
NPL Status:  Currently on the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R03-93/174
ROD Date:  09/29/1993
Operable Unit(s):  09
Media:  GW
Contaminant:  VOCs
Abstract:  The 71-acre U. S. Defense General Supply Center site is a supply and storage facility within the 640-acre Defense Logistics Agency located in Chesterfield County, Virginia. Land use in the area is predominantly residential, commercial, and light industrial, with a wetlands area located along the eastern edge of the site. Land surface at the site has been altered extensively by grading and filling operations, and surface drainage from the site flows into No Name Creek, ultimately reaching the James River less than two miles away from the site. Of the estimated 2,200 residents who live within one mile downgradient of the site, 10 residences use ground water for their drinking water supply; and many more use ground water for household activities. The site has been divided into three distinct geographic areas for remediation, which include the Open Storage Area (OSA), Area 50, and the National Guard Area (NGA). Since 1942, the 43acre OSA has been used as a storage lot for bulk drummed chemicals. The majority of the 55-gallon drums contain petroleum oils and lubricants (POLs), but solvents, pesticides, herbicides, and other chemicals also are stored in this area. The northern end of the OSA was also a former drum recoupment area, which operated from the early 1960s until 1982. Area 50 is approximately 13 acres and was used as a landfill for construction debris and damaged containers of solid and liquid stock chemicals in the 1960s and 1970s. Some of the contaminants disposed of in the area include photographic development chemicals, organic solvents, pesticides, herbicides, POLs, and PCBs. The NGA is a 15-acre area which was leased to the Virginia Army National Guard beginning in the 1950s. The NGA is currently used for vehicle maintenance operations which include engine cleaning and degreasing, fluid changes, lubrication, and engine rebuilding, all of which required the use of chlorinated and non-chlorinated solvents. In the past, underground and above-ground storage tanks in this area were used to store fuels, oils, and solvents. In 1984, EPA initiated investigations at the site which later revealed contamination of the soil and ground water by petroleum products, chlorinated and non-chlorinated solvents, pesticides, herbicides, and metals from improper chemical handling and storage activities conducted in the late 1950s and 1970s. Two 1992 RODs addressed source contamination in two separate areas, as OUs 1 and 5, respectively. This ROD addresses an interim remedy for the ground water, as OU9. Six future RODs are planned for the site; three will address source contamination as OUs 2, 3, and 4, and three will address ground water contamination as OUs 6, 7, and 8. The primary contaminants of concern affecting the ground water are VOCs, including benzene, PCE, and TCE. SELECTED REMEDIAL ACTION: The selected interim remedial action for this site includes extracting and treating ground water using air stripping; controlling air emissions using activated carbon adsorption, followed by either offsite treatment or offsite disposal of the spent activated carbon; discharging the treated ground water onsite to a series of infiltration trenches; and monitoring the ground water. The estimated present worth cost for this remedial action is $594,067, which includes an estimated annual O&M cost of $46,000. PERFORMANCE STANDARDS OR GOALS: Final goals for ground water have not been determined and will be implemented as part of OU6. Chemical-specific ground water interim action levels are based on SDWA MCLs or MCLGs, and include benzene 5 ug/l; PCE 5 ug/l; and TCE 5 ug/l. INSTITUTIONAL CONTROLS: Not applicable.
Remedy:  This operable unit is the third of nine operable units that are currently being addressed at the DGSC. OU9 addresses interim treatment and containment of groundwater in the upper and lower aquifers beneath Area 50, the OSA, and the NGA. The other OUs, and the portions of the Site that each addresses are as follows:
- OU1-Open Storage Area Source Area
- OU2-Area 50 Source Area
- OU3-National Guard Area Source Area
- OU4-Fire Training Area Source Area
- OU5-Acid Neutralization Source Area
- OU6-OSA/Area 50/NGA Groundwater (Final Remedy)
- OU7-Fire Training Area Groundwater
- OU8-Acid Neutralization Pits Groundwater

RODs addressing OU1 and OU5 were signed in March and May 1992, respectively, and are currently being implemented.

OU6 and OU9 are the same geographic location. OU9 relates to interim treatment of the contaminated groundwater. OU6 relates to the final groundwater remedy for this location.

The primary objectives of this remedy for OU9 are to reduce risk to human health by impeding further spread of groundwater contaminated with volatile organic compounds (VOCs) in OU9 through groundwater extraction and treatment before the final remedial action is implemented, to lessen the migration of contaminated groundwater, to initiate the reduction of toxicity, mobility, and volume of the contaminants in the groundwater, and to collect data regarding changes in the aquifer and contaminant concentrations in response to remediation measures. This remedy is considered an interim action. Final cleanup goals for groundwater have not yet been determined. A final action that addresses the groundwater (OU6) will be selected after data generated during the implementation of this interim action are evaluated. This interim action for OU9 is expected to become part of the final action for OU6 and to provide for significant risk reduction early in the remedial process.

The major components of the selected remedy include:
* Withdrawal of contaminated groundwater from unconsolidated deposits through a series of extraction wells and intercepting trenches;
* Conveyance of contaminated groundwater through a pipe network to an on-site treatment facility;
* Treatment of contaminated groundwater through air stripping of VOCs and activated carbon treatment of related air emissions sufficient to meet Federal and State Applicable or Relevant and Appropriate Requirements (ARARs) for air and the receiving aquifer;
* Discharge of treated groundwater to a series of percolation trenches on DGSC property;
* Off-site disposal or treatment of spent activated carbon used to control air emissions of VOCs.
* Periodic groundwater monitoring to evaluate the performance and effectiveness of the groundwater extraction, treatment, and percolation system, and to establish final cleanup goals; and,
* Modification of the system as necessary based on periodic monitoring.
Text:  View full-text ROD [ 58K ]
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