Superfund record of decision (EPA Region 4): Savannah River Site (USDOE), Motor Shops Seepage Basin (716-A), Aiken, SC, June 26, 1998

The Motor Shops Seepage Basin (716-A) (MSSB) is listed as a Resource Conservation and Recovery Act (RCRA) 3004(u) solid waste management unit/Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) unit in Appendix C of the Federal Facility Agreement (FFA) (FFA 1993) for the Savannah River Site (SRS), in Aiken, South Carolina. The selected alternative was developed in accordance with CERCLA, as amended, and to the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). The selected remedy for MSSB is No Action. Investigation of this operable unit was performed to determine if hazardous substances had been released to the environment. The Baseline Risk Assessment indicated that there were no significant releases to the environment. Therefore, it appears that either there were no significant discharges of hazardous materials to the seepage basin or natural remediation processes (i.e., bioremediation) have reduced the levels of hazardous materials to the extent that they no longer pose risk to human health or the environment. The Baseline Risk Assessment considered both the future residential and future industrial land use scenarios. Benzo(a)pyrene was the only preliminary constituent of concern (human health) detected in the soil at MSSB. Benzo(a)pyrene was detected only in the top foot of soil at levels which give risk values greater than 1 x 16-6 (but less than 1 x 10-4) for the future adult/child resident. Further uncertainty analysis indicated that benzo(a)pyrene should not be considered a constituent of concern for the MSSB due to: (1) low frequency of detection; (2) unit history that strongly suggests it came from an adjacent source; and (3) conservative methodology was utilized in the risk assessment. No ecological or contaminant migration constituents of concern were identified at this unit. Therefore, No Action is the appropriate remedy and a five year ROD review will not be required. The South Carolina Department of Health and Environmental Control has modified the SRS RCRA permit to incorporate the No Action remedy