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a' s Chevron/S. E1 Dorado 15 August 1990 in Concord, California. The water samples were analyzed for the presence of STEX and TPH-as-gasoline using modified EPA Methods 5030/8020/8015. Samples from MW-1 were analyzed for TPH-as- diesel using EPA Method 8015, for the presence of TOG using EFA Method 3550/ APHA SM 5038, for TPH-as-waste--oil using APHA SM 503 E/IR, and for the presence of Cd, Cr, Pb, and Zn using EPA Methods 7005/6010. SUBSURFACE CONDITIONS SCILS The subsurface conditions encountered during this investigation consisted prinarily of sandy and clayey silts to an approximate depth of 48.0-feet below ground surface. From f approximately 48.0-feet to 58.0-feet below grade the sediments consisted of silty and clayey sands. In all three borings groundwater was encountered at approximately 47.0-feet to 48.0-feet below ground surface. Subsequent water level measure- ments indicate that the water level rose to approximately 40.0- feet below ground surface. The groundwater appears to be con-- tained within the pore spaces of the silty fine-grained sands and silts encountered below 49 feet with the sandy and clayey silts above that depth creating semi-confined conditions at the site. r+ Field screening by headspace analyses with a PIU indicated that soil samples collected from monitoring well MW-1 at a depth �. of 18.0 feet, 34.0 feet, and 39.0 feet contained detectable ! , volatile hydrocarbon vapors at 20 ppm, s0 ppm, and 15 ppm, respectively. All samples field screened from monitoring wells MW-2 and MW-3 were below 3 ppm. The PID readings are listed on the boring logs included in Appendix F. Based on field T - -- -- ----- ---observations,--proximity---to-the-water table, and-PID-readings, - - samples from each boring were submitted for laboratory analyses. The results of the laboratory analyses are summarized in Table 3. The laboratory report is included in Appendix H. ---� GNOI'51111iYTF:N „ TF xIi\O DGY.INC.