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February 16, 1992 Working To Restore Nature <br /> BP OR Facility No. 11195, Lathrop, California- <br /> The <br /> aliforniaThe groundwater sample collected from monitoring well MW-5 was additionally analyzed <br /> for TPHd using EPA Methods 355018015, TOG using Standard Method 5520, and HVCs <br /> .i using EPA Method 601. <br /> 9 The results of the laboratory analyses of soil and groundwater samples are summarized in Table 2 <br /> and Table 3. The laboratory reports and Chain of Custody records are included in Appendix E. <br /> 4.0 DISCUSSION OF RESULTS <br /> The results of the field activities and laboratory analyses of soil and groundwater samples collected <br /> during this preliminary investigation are discussed below. <br /> < Soil encountered in borings B-1 through B-5 generally consists of clay, silt, and sand to a <br /> depth of approximately 24.5 feet below grade. <br /> • Residual gasoline hydrocarbons were detected in the soil samples collected from boring B- <br /> 3, drilled adjacent to the south end of the underground fuel storage tanks. <br /> • Detectable concentrations of residual gasoline hydrocarbons were not present in soil <br /> samples analyzed from borings B-1,B-2, and B-4, drilled adjacent to the dispenser islands <br /> and associated piping, and the north end of the underground fuel storage tanks. <br /> e=rr • <br /> • Detectable concentrations of gasoline hydrocarbons, diesel fuel, total oil and grease, and <br /> halogenated volatile compounds were not present in soil samples analyzed from boring B- <br /> E 5, drilled adjacent to the underground used-oil tank. <br /> € Groundwater was encountered in borings B-1 through B-5 during drilling at depths <br /> ranging from 12.0 feet to 13.5 feet below ground surface. After development, the static <br /> groundwater surface was approximately 11.0 feet to 14.0 feet below ground surface. <br /> Groundwater elevation data collected on December 21, 1992 indicated the groundwater <br /> flow direction ranged from southwest to southeast; the average hydraulic gradient was <br /> .� 0.0008. <br /> Total petroleum hydrocarbons as gasoline (TPHg) and benzene were detected in <br /> groundwater samples collected from the wells at maximum concentrations of 10,000 ppb <br /> (well MW-4) and 6.7 ppb (well MW-3). The highest concentrations of gasoline <br /> - :� hydrocarbons in groundwater were detected in wells near the existing fuel tank complex. <br /> F 17 05 2.01 4 <br /> r:h <br />