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June 30, 1992 �ACff�A Unocal Station No. 6981, Stockton, California Selected soil samples from borings B-6 through B-8 and B-10 through B-13 were submitted to RESNA Analytical Laboratories in Fremont, California (Hazardous Waste Testing Certificate No 1211), for analysis of total petroleum hydrocarbons as gasoline (TPHg) and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using Environmental Protection Agency (EPA) Methods 8015/5030 and 8020, respectively. Sample S-50-B8 was analyzed for total lead using EPA Method 7241 as requested by San Joaquin County. One composite sample of the drill cuttings was analyzed for organic lead using the California LUFT Manual Method Analytical results of the soil samples are shown on Table 1 Copies of the Chain of Custody Records and laboratory Analysis Reports are attached Gasoline hydrocarbons were detected in soil samples from borings B-6, B-7, B-8, B-11, B-12, and B-13. The highest concentrations of gasoline hydrocarbons, 5,300 parts per million (ppm) TPHg and 17 ppm benzene, were detected in samples from boring B-11 Gasoline hydrocarbons were not detected in soil samples collected from boring B-10. Total lead was detected in the sample collected from 50 feet below grade in boring B-8 (S-50-B8); however, the concentration was below the soluble threshold limit concentration Organic lead was not detected in the composite sample Ground-Water Sampling and Evaluation of Ground-Water Gradient On March 9, 1992, a technician from RESNA checked monitoring wells MW-1 through MW-8 for free product, measured depths to water, and collected water samples from wells MW-6, MW-7, and MW-8 for laboratory analyses Monitoring wells MW-1 through MW-5 were not sampled because of insufficient water volume in the wells. No free product or sheen was noted in the wells (Table 2) Field procedures are described in an attachment to this report. The manifest for disposal of the water is attached. Water samples were also submitted to RESNA Analytical Laboratories in Fremont, California, for analysis of TPHg and BTEX using EPA Methods 8015/5030 and 602, respectively Water samples from wells MW-7 and MW-8 were also submitted to FGL Environmental of Stockton, California, and analyzed for total and fecal coliform bacteria using Standard Methods, 15th Edition, American Public Health Association. Analytical results of the water samples are shown on Tables 3 and 4 Gasoline hydrocarbons were detected in water samples collected from monitoring wells MW-7 and MW-8 but not in the sample from well MW-6 The highest concentrations of gasoline hydrocarbons were detected in the water sample from well MW-7 (13,000 parts per billion [ppb] TPHg and 1,400 ppb benzene) Total coliform bacteria were detected in water samples from wells MW-7 and MW-8; fecal coliform bacteria were not detected in these water samples. 46 03052-71 38032-7 3