SITE INFORMATION AND CORRESPONDENCE

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Pre-Design Technical Sumly -3- • 19 December 1996 DDRW-Sharpe Location Lead me/ke Chromium me/ke Comment 9E(2-3ft) 27,500 by laboratory analysis 9E(5-6ft) 17,700 by laboratory analysis SB29-B9 (2-2.5) 1,541 by laboratory analysis SB29-B4 (8-9ft) 1,421 (12.5-13.5ft) 329 by XRF SB29-B 12 (8.5-9.5) 1,364 by XRF 50E-1H (3-4ft) 3,990 368 by laboratory analysis 50E-1F (14-14.5ft) 722 by XRF 50E-1G (3-4ft) 1,160 by laboratory analysis 50E-1 G(6-7ft) 1,140 by laboratory analysis Based on this data the ROD recommended that the extent of metals contamination be reevaluated to determine the volume of contaminated soils that required excavation. The Pre-Design Technical Summary reports that none of the surface soil samples collected in the South Balloon area during this field work indicated total chromium levels greater than 300 mg/kg or total lead levels greater than 1000 mg/kg. Since excavation only to a depth of 2 feet BGS is required in the ROD, it would not be practical to proceed with this remedial action. The conclusion in the Pre-Design Technical Summary recommends continued monitoring only in the South Balloon area because none of the samples collected during this field work exceeded action levels for either lead or chromium. Because elevated concentrations are documented for the seven areas noted above, we can not be support the recommendation to merely continue monitoring in the South Balloon for metals as currently performed. Because concentrations above action levels have been found below 2 feet BGS during past work, and we continue to observe elevated concentrations of metals in the ground water ( e.g. monitoring well 403A and 424 A) down gradient of area 529, this area is still considered to be a threat to water quality. In order to comply with the ARARs established in the OU2 ROD for areas where lead and chromium contaminated soils are determined to be a potential threat to water quality, an evaluation monitoring program as outlined under 22 CCR Div. 4.5, Chapter 14, Article 6 must be implemented. A statistical analysis of the metals concentrations found in ground water should be performed to determine the significance of the increases in concentrations observed. Additional characterization of the vadose zone is needed to further delineate the source of leachable metals in the area of the bum pits (5-29). In addition, at least one monitoring well down gradient of the burial pits (5-36) in the vicinity of Building 605 is necessary to allow for the detection of a release from this disposal site area.