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shipped by overnight couner to a State of California, Department of Health Services (DHS)-certified hazardous waste laboratory. A sample was not submitted from the 10- to 15-foot interval of SB-8 due to low sample recovery. Soil remaining in the spirit-spoon sampler was logged by an experienced ES geologist, visually inspected for signs of staining, and screened for the presence of organic vapors with a photolomzation detector (PID) Based on the soil data, two geologic cross-sections of the site stratigraphy were prepared (Figures 4a and 4b). 1 Cross section locations are shown on Figure 3. Soil boring logs are presented in Appendix A. Groundwater Elevation Measurements Groundwater levels were measured in the existing monitoring wells with an electric water level indicator on August 30, 1994 (Table 1) As described in the August ' groundwater monitoring report, these measurements nndlcate that shallow groundwater was flowing southward under an estimated hydraulic gradient of 0.003 feet per foot. No free product or hydrocarbon sheens were observed when the water level measurements were taken ANALYTICAL RESULTS The soil samples were analyzed for BTEX using EPA Method 8020 and TP14D using the DHS/LUFT-approved method (modified EPA Method 8015). The reporting limits were 1 µg/kg (BTEX) and 1 mg/kg (TPHD) All analyses were performed at a DHS-certified hazardous waste laboratory. Soil Sample Analytical Results ' A total of 71 samples were collected and submitted for laboratory analyses. Total BTEX concentrations ranged from non-detect to 3,910 µg/kg. TPH-D concentrations ranged from non-detect to 16,000 mg/kg. Analytical results for soil samples are ' summarized In Table 2 and presented as overlays on Figures 4a and 4b. Additionally, soil analytical data are plotted on Figure 5 which also illustrates the zero and 10 ppm lsoconcentration lines for known HD contamination on-sate. Complete, certified ' analytical reports and chain-o -custody records are presented in Appendix B. DISCUSSION ' The analytical results from the SSA and previous investigations are combined in Figure 5 to estimate the TPHD "zero line", indicating the on-site lateral extent of TPHD in soul with concentrations exceeding the laboratory practical quantitation limit. L The estimated area enclosed by the zero line is 4,800 square feet. The area containing soil with TPHD concentrations exceeding 10 ppm, 2,400 square feet, is also shown in Figure 5. As indicated, the extent of contamination adjacent to and west of the 1 Greyhound facility has not been determined and should be investigated with a limited off-site drilling program in order to define the zero line west of the site. Assumun the lateral extent of TPHD contamination noted above, and a vertical extent of sigmfimt TPHD concentrations of 35 feet (based on the relatively high concentrations reported in samples obtained from borings SB-2, SB-7, and SB-8), soil A)' =,t_ PAMSYR01\VOLI wP170386 08969125386R02 DOC 4