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1 . 0 INTRODUCTION <br /> J <br /> This submittal presents Aqua Science Engineers, Inc. (ASE)'s workplan for <br /> a soil and groundwater assessment at the Unocal Service Station located <br /> at 574 West Grant Line Road in Tracy, California (Figure 1). This work is <br /> being conducted on behalf of Mr. Satnam Singh, owner of the property, as <br /> required by the San Joaquin County Public Health Services, Environmental <br /> Health Division (PHS-EHD) in their letters dated August 4, 1998 and <br /> December 7, 1998 (Appendix A). <br /> f: <br /> 2 . 0 BRIEF SITE HISTORY AND BACKGROUND INFORMATION <br /> In March 1998, ASE drilled eight soil borings at the site using a Geoprobe <br /> hydraulic sampling rig (Figure 2). Borings BH-A, BH-B and BH-C were <br /> located to the north, northwest and west of the fuel dispensers, <br /> f respectively. Borings BH-D, BH-E and BH-F were located to the west, <br /> northwest and north of the underground storage tank (UST) complex, <br /> respectively.Y• Boring BH-G was <br /> located near <br /> the northeast corner of the <br /> site, and boring BH-H was located near the northwestern corner of the <br /> site. Sediments encountered during drilling generally consisted of sandy <br /> silt from the ground surface to the total depth explored of 10-feet below <br /> ground surface (bgs). Groundwater was encountered at approximately k <br /> 6.5-feet bgs. Hydrocarbons were detected in soil samples collected from ' <br /> the capillary zone in all of the borings except boring BH-B. The highest <br /> concentrations were in borings BH-E and BH-F which contained up to <br /> 4,300 parts per million (ppm) total Petroleum <br /> hydrocarbons as gasoline <br /> (TPH-G), 24 ppm benzene, 48 ppm toluene, 70 ppm ethyl benzene, a n d <br /> 390 ppm total xylenes. Benzene concentrations exceeded United States <br /> Environmental Protection Agency (US EPA) Region IX preliminary <br /> remediation goals (PRGs) for industrial soil in soil samples collected from <br /> borings BH-A, BH-D, BH-E, BH-F and BH-G. Methyl tertiary butyl ether <br /> (MTBE) and total xylene concentrations also exceeded US EPA PRGs for <br /> industrial soil in soil samples collected from several borings. ' Total lead <br /> concentrations in soil samples collected from borings BH-A through BH-H <br /> ranged from Iess than 5.0 ppm to 10 ppm. None of these concentrations <br /> exceeded PRGs. Hydrocarbons were also detected in groundwater samples <br /> collected <br /> from all of the borings. The highest concentrations <br /> were in <br /> groundwater samples collected from borings BH-D, BH-E and BH-F which <br /> contained up to 120,000 parts per billion (ppb) TPH-G, 20,000 p p b <br /> benzene, 14,000 b toluene 5 700 b ethyl h 1 benzene <br /> Pp y 21,000 ppb total <br /> xylenes, and 59,000 ppb MTBE. Benzene concentrations exceeded <br /> California Department of Toxic Substances Control (DTSC) maximum <br /> contaminant levels (MCLs) for drinking water in groundwater samples 1 <br /> 574 West Grand Line Road, Tracy, CA Workplan — June 2000 <br />