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Working To Restore Nature <br /># February 12, 1993 <br /> r BP Oil Facility No. 11393, Stockton, California. <br /> • Groundwater samples from monitoring wells MW-1 through MW-4 were analyzed <br /> ' for TPHg using EPA Methods 5030/8015 (modified) and BTEX using EPA Methods <br /> 5030/8020 (modified). <br /> ' Groundwater samples from monitoring well MW-4 were also analyzed for TPHd <br /> using EPA Methods 3550/8015, TOG using Standard Method 5520, and HVCs using <br /> 1 EPA Method 601. <br /> The results of laboratory analyses of soil and groundwater samples are summarized in <br /> Table 2 and Table 3. The laboratory reports and Chain of Custody records are included in <br /> Appendix F. <br /> 4.0 DISCUSSION OF RESULTS <br /> The results of the field activities and laboratory analyses of soil and groundwater samples <br /> ' collected during this preliminary investigation are discussed below. <br /> • Groundwater was encountered in borings B-1 through B-4 during drilling at depths <br /> of approximately 21 feet below grade. After development, the static groundwater <br /> surface was approximately 20.5 feet to 22.0 feet below grade. <br /> ' Groundwater elevation data collected on December 21, 1992 indicated the <br /> groundwater flow direction was to the northwest; the average hydraulic gradient was <br /> 0.002. <br /> Soil encountered in borings B-1 through B-4 generally consists of clay, silt, and sand <br /> to approximately 36.5 feet below grade_ <br /> ' Concentrations of TPHg were not detected in soil samples collected from borings B-1 <br />• and B-2, drilled adjacent to the underground fuel-storage tanks. However, BTEX <br /> ' compounds were detected in the samples from 15 and 20 feet below grade in boring <br /> B-1 and 21.3 feet below grade in boring B-2 at a maximum concentration of 0.087 <br /> parts per million. <br /> Q Detectable concentrations of TPHg and BTEX were not present in soil samples from <br /> borings B-3, drilled adjacent to the dispenser islands and associated piping. <br /> ' Concentrations of TPHg, BTEX, TPHd, TOG, and HVCs were not detected in soil <br /> samples from boring B-4, drilled adjacent to the underground used-oil tank. <br /> 1701.01 4 <br />