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1 <br /> r <br /> +•• 1 . 0 INTRODUCTION <br /> This submittal presents Aqua Science Engineers, Inc_ (ASE)'s workplan f o r <br /> a soil and groundwater assessment and remediation feasibility study at the <br /> Unocal Service Station located at 574 West Grant Line Road in Tracy, <br /> California (Figure 1). This work is being conducted on behalf of Mr. <br /> Satnam Singh, owner of the property; as requited by the San Joaquin <br /> County Public Health Services. Environmental Health Division (PHS EHD) <br /> in their 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 . March 1999—Soil Borin2 <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 /> ..r 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 (ppm) total petroleum hydrocarbons as gasoline <br /> (TPH-G), 24 ppm benzene, 48 ppm toluene, 70 ppm ethyl benzene, and <br /> 390 ppm total xylenes. Total lead concentrations in soil 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 up <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, and <br /> 59,000 ppb MTBE. <br /> 574 West Grand Line Road, Tracy, CA Workplan – ApriI 2001 <br /> -1- <br />