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30 INVESTIGATIVE FUNDINGS 331 Site Geology The geologic conditions at borings VW-1, VM-1, and VM-2 generally consisted of fill soil overlying alluvial deposits The fill soil was encountered to depths of between 3 and 15 feet bgs The fill soil at ' VW-1 and VM-2 existed to depths of approximately 3 and 10 feet bgs, respectively, and was generally comprised of sandy gravel The fill soil at VM-1 existed to a depth of approximately 15 feet bgs and was generally comprised of fine to medium silty sand The alluvial deposits encountered underlying the fill soil generally consisted of alternating strata of silty clay, clayey silt, and silty sand Detailed descriptions of the soil conditions encountered are presented on the Boring Logs included in Appendix A A northwest-southeast trending geological cross-section depicting soil stratigraphy between well MW-19 and boring SB-17 is presented as Figure 3 ' 332 Site Hydrogeology On October 23, 1996, the groundwater depths within the investigation area ranged from ' approximately 59 4 to 60 5 feet below the top of well casings, or approximately -37 9 to -38 4 with respect to Mean Sea Level The direction of groundwater flow was generally to the east with a ' radient of approximately 0 003 ft/ft A cumulative summary of the groundwater depth and elevation measurements is presented on Table 3 Groundwater elevation contours and the groundwater flow direction and gradient for October 23, 1996 are depicted on the Groundwater Elevation Map - October 1996, Figure 4 3.3 Soil Sample Analytical Results ' Selected soil samples collected from borings VW-1, VM-1, VM-2, MW-25 and MW-26 were tested for the presence of TPHg and BTEX and MTBE The laboratory results of the soil sampling performed for this phase and previous phases of investigation are presented on Table I Copies of the laboratory reports and cham-of-c u stody documentation for the soil samples collected from VW-1, ' VM-1, VM-2, MW-25 and MW-26 are presented in Appendix B Soil samples collected from VW-1 at depths of between approximately 15 and 45 feet bgs exhibited TPHg concentrations ranging from 7 0 to 13,000 mg/kg The remaining soil samples collected from VW-1, including those collected from below the groundwater surface, did not exhibit detectable concentrations of TPHg Soil samples collected from VW-1 at depths of approximately 35, 40, 45, ' 60, and 85 feet bgs exhibited benzene concentrations of between 0 011 and 2 1 mg/kg Soil samples collected at depths of approximately 40, 50, and 65 feet bgs from boring VM-1 were analyzed for TPHg and BTEX The soil sample collected at a depth of approximately 40 feet exhibited a TPHg concentration of 6 3 mg/kg and a benzene concentration of 0 58 mg/kg The soil ' sample collected at a depth of approximately 50 feet exhibited a TPHg concentration of 1 6 mg/kg and a benzene concentration of 0 27 mg/kg The soil sample collected at a depth of approximately 65 feet did not exhibit detectable concentrations of TPHg or BTEX Project No 58100-06-1$A -9- December 9, 1996