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3.0 FINDINGS 3.1 GEOLOGIC AND HYDROGEOLOGIC CONDITIONS Soils beneath the Site were investigated to a maximum depth of 59 feet during this and previous 1 investigations. Lithologic information from soil borings advanced during this investigation indicate the Site is underlain by unconsolidated alluvium composed predominantly of sand with lesser and variable amounts of silt and clay. In each of the three borings advanced during this investigation, soils encountered to the depths explored consisted of alternating layers of brown, yellowish brown to reddish sand and silty sand. Groundwater was first encountered during drilling at a depth of approximately 45 feet below ground ' surface. Stabilized groundwater levels were measured in wells MW-1A, MW-2, and MW-3 on January 15, 1993. Reference elevations (top of PVC casing), ground surface elevations, depth to groundwater, and corresponding groundwater elevations are shown in Table 1. Groundwater elevations were used to construct the groundwater elevation contour map shown on Figure 3. Interpretation of the groundwater elevation map shows groundwater flow in the water table zone is towards the southeast under a hydraulic gradient of approximately 0.008 foot per foot (ft/ft). ' 3.2 SOIL ANALYSIS RESULTS 3.2.1 Monitoring Wells TPHg and BTEX were not detected above the laboratory reporting limits in soil samples collected ' from the boreholes for monitoring well MW-2 and MW-3. Complete laboratory data sheets including quality assurance/quality control (QA/QC) data are included in Appendix D. 3.2.2 Conrirmatory Soil Boring Analytical testing results for soil samples collected from the confirmatory g soil boring are shown in Table 2. With the exception of a soil sample collected from 30 feet (CSB-1-6), other soil samples I were reported to exhibit no detectable TPHg concentrations (1 ppm reporting limit). A TPHg concentration of 1 ppm was reported in the sample from 30 feet. The laboratory reported the chromatogram pattern for this sample was a non-standard gasoline pattern. The non-standard gasoline pattern observed in this sample is likely the result of degradation of the gasoline via processes such as biodegradation and volatilization induced by vapor extraction. ' Benzene, toluene, and ethylbenzene were not detected above the laboratory reporting limit of 0.003 ppm in soil samples collected from the confirmatory soil boring. Total xylenes were reported to be present in detectable levels in two samples. Xylenes were detected at 0.007 and 0.10 ppm in samples ' collected from 20 and 30 feet, respectively. Complete laboratory data sheets including quality assurance/quality control (QA/QC) data are included in Appendix D. MARDEE,RPT 50014-003-01 MD04 8