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r I . 0 INTRODUCTION <br /> This report presents Aqua Science Engineers, Inc. (ASE's) soil a n d <br /> groundwater assessment and corrective action plan (CAP) for the Unocal <br /> Service Station located at 574 West Grant Line Road in Tracy, California <br /> (Figures 1 and 2). This work was conducted on behalf of Mr. Satnam <br /> Singh, owner of the property, as required by the San Joaquin County <br /> Public Health Services, Environmental Health Division (PHS-EHD) in their <br /> directive dated March 9, 2001 (Appendix A). <br /> 2 . 0 BRIEF SITE HISTORY AND BACKGROUND INFORMATION <br /> The site is currently operating as a Unocal 76 gasoline service station, <br /> with an attached convenience store. <br /> 2. 1 Pdarch 199& Soil BerinRs <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 fuer ' dispensers, <br /> 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. Boring BH-G was located near 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 <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 (ppin) total petroleum hydrocarbons as gasoline <br /> (TPH-G), 24 ppm benzene, 48 ppm toluene. 70 ppm ethyl benzene, a n d <br /> 390 ppm total xylenes. Total lead concentrations in ;oil samples collected <br /> from borings BH-A through BH-H ranged from less than 5.0 ppm to 10 <br /> ppm. Hydrocarbons were also detected in groundwater samples collected <br /> from all of the borings. The highest concentrations were in groundwater <br /> samples collected from borings BH-D, BH-E and BH-F which contained u p <br /> to 120,000 parts per billion (ppb) TPH-G, 20,000 ppb benzene. 14,000 <br /> ppb toluene, 5,700 ppb ethyl benzene, 21 ,000 ppb total xylenes, a n d <br /> 59;000 ppb methyl tertiary butyl ether (MTBE). <br /> 574 West Grant Line Road CAP — January 2002 <br />