SITE INFORMATION AND CORRESPONDENCE_1992

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• Draft Soils FS Report Memorandum -4- 17 April 1992 DDRW, Sharpe detail in the memorandum on the pilot VES. In addition, the two USTs which contained waste solvents appear to have been inadequately investigated and need additional investigation to determine if soils and ground water are contaminated in the surrounding areas of the USTs. Finally, it is unclear why only two soil sites have been identified as needing remediation when there are more than two distinct VOC plumes. 10. Remediation by capping is proposed for some areas with lead contaminated soils. Capping of the lead contaminated soils is unacceptable based on the existing data base. Because the solubility of the lead in the contaminated soils is unknown and because the ground water is relatively shallow ground water (and may be less than five feet depending on the depth of the WMU or UST) , capping of the contaminated soils may be inadequate to protect ground water quality. Ground water could continue to be degraded if the unsaturated zone is thin, the lead is soluble and ground water levels fluctuate. Additional information on the solubility of lead, the thickness of the unsaturated zone beneath the WMU or UST and the historical high ground water elevation is needed to determine if capping is an acceptable remedial alternative. Chapter 15 of the California Code of Regulations (CCR) must be complied with if any soil contamination is left in-place and may degrade water quality. 11 . Many of the state Applicable or Relevant and Appropriate Requirements (ARARs) were not identified in the Draft Soils FS Report. Of particular concern, is that Chapter 15, Division 3, Title 23 of the Water Code was not identified. This promulgated ARAR has location, action and chemical specific requirements for waste discharges to land. The WMUs (sump at Building S-119) which contain hazardous waste constituents are subject to the Toxic Pits Cleanup Act (TPCA) if the hazardous wastes were stored in the sump after 1 January 1985. The requirements of the TPCA must be considered as an ARAR. In addition, the requirements of Chapter 16 of the CCR must be complied with for fuel USTs. The FS Report needs to be revised to include these ARARs. We have enclosed a table which identifies our ARARs. More specific ARARs will be provided as remedial measures are developed. SPECIFIC COMMENTS a. Depth of Soil Borings. The depth of many of the soil borings extended only to 15 feet below ground surface (bgs) . It is unclear whether the borings extended to the ground water table. In addition, in some of the borings (S13-B2 at Building 391, PS7-B1 at Buildings T-661 and 669) , the contaminant concentrations were found to be the highest of the deepest soil samples. If the ground water table is greater than 15 feet bgs, it is possible that the contaminant concentrations further increase downward in the unsaturated zone. The vertical extent of contamination in the unsaturated zone needs to be defined for each constituent of concern. b. Composite Soil Samples. The soils boring samples and surface samples were frequently composited over depth. The contaminant concentrations in composite samples are generally less than for grab samples. Because composite samples were collected over five foot intervals in the soil borings, estimates of total contaminated soil are affected which would lead to over or under estimates of the volume of soils above cleanup levels needing remediation.