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dJ „y • 1 . 0 INTRODUCTION This submittal presents Aqua Science Engineers, Inc (ASE)'s report for a soil and groundwater assessment at the Unocal Service Station located at 574 West Grant Line Road in Tracy, California (Figure 1) This work was conducted on behalf of Mr Satnam Singh, owner of the property, as required by the San Joaquin County Public Health Services, Environmental Health Division (PHS-EHD) in their letters dated August 4, 1998 and December 7, 1998 (Appendix A) 2 . 0 BACKGROUND INFORMATION In March 1998, ASE drilled eight soil borings at the site using a Geoprobe hydraulic sampling rig (Figure 2) Borings BH-A, BH-B and BH-C were located to the north, northwest and west of the fuel dispensers, respectively Borings BH-D, BH-E and BH-F were located to the west, northwest and north of the underground storage tank (UST) complex, respectively Boring BH-G was located near the northeast corner of t h e site, and boring BH-H was located near the northwestern corner of the site Sediments encountered during drilling generally consisted of sandy silt from the ground surface to the total depth explored of 10-feet below ground surface (bgs) Groundwater was encountered at approximately 6 5-feet bgs Hydrocarbons were detected in soil samples collected from the capillary zone in all of the borings except boring BH-B The highest concentrations were in borings BH-E and BH-F which contained up to 4,300 parts per million (ppm) total petroleum hydrocarbons as gasoline (TPH-G), 24 ppm benzene, 48 ppm toluene, 70 ppm ethyl benzene, and 390 ppm total xylenes Benzene concentrations exceeded United States Environmental Protection Agency (US EPA) Region IX preliminary remediation goals (PRGs) for industrial soil in soil samples collected from borings BH-A, BH-D, BH-E, BH-F and BH-G Methyl tertiary butyl ether (MTBE) and total xylene concentrations also exceeded US EPA PRGs for industrial soil in soil samples collected from several borings Total lead concentrations in soil samples collected from borings BH-A through BH-H ranged from less than 5 0 ppm to 10 ppm None of these concentrations exceeded PRGs Hydrocarbons were also detected in groundwater samples collected from all of the borings The highest concentrations were in groundwater samples collected from borings BH-D, BH-E and BH-F which contained up to 120,000 parts per billion (ppb) TPH-G, 20,000 p p b benzene, 14,000 ppb toluene, 5,700 ppb ethyl benzene, 21,000 ppb total xylenes, and 59,000 ppb MTBE Benzene concentrations exceeded California Department of Health Services (DHS) maximum contaminant levels (MCLs) for drinking water in groundwater samples collected from 574 West Grant Line Road Report — October 2000 - l -