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rIle, <br /> EXECUTIVE SUMMARY <br /> This report has been prepared by Pacific Environmental Group, Inc. (PACIFIC) to <br /> document the findings of a soil and groundwater investigation performed at'UNOCAL <br /> Bulk Plant No.0788 located at 8203 East 11th Street in Tracy, California. A summary <br /> of investigative findings is presented below: <br /> o A partially buried 5,000-gallon transmission fluid storage tank;was <br /> t removed.from the southeastern portion of the site on.D "'ember°13 <br /> 1989: ` Analytical results indicated that low levels of petroleum <br /> f hydrocarbons remained in the soils adjacent to the excavation. <br /> f <br /> j o The San Joaquin County Public Health Services Department issued an <br /> "Unauthorized Storage Tank Release/Contamination Site Report" on <br /> January 30, 1990,and requested additional investigation. <br /> o PACIFIC.installed three groundwater monitoring wells (U-1 tt,rough <br /> U-3)on October 24 and 25, 1990. <br /> o The site is underlain by primarily fine.grained deposits (silts and clays) <br /> to the total depth explored of 27 feet. Sands were observed in each of <br /> f the borings at depths of approximately 17 to 25-1/2 feet below ground <br /> surface with thicknesses ranging from 1-1/2 to 5 feet. <br /> Io Static groundwater occurred at a depth of approximately 9-1J2 feet <br /> below grade during November 1990 with a calculated north- <br /> northwesterly gradient of 0.006. <br /> o Selected soil samples were analyzed for TPH gasoline, TPH diesel, <br /> halogenated volatile organics (EPA 8010), and benzene, toluene, l <br /> ethylbenzene, and total xylenes (BTEX . compounds). The <br /> hydrocarbon concentrations range from ND to 1,800 parts per million <br /> ' (ppm)TPH gasoline, and from ND to 710 ppm TPH diesel at the.5.to, <br /> i 6-1/2 foot interval. The concentrations attenuate to non-detectable <br /> levels at the 10 to 11-1/2 foot interval with the exception of 3.2 and <br /> f 5.2 ppm TPH diesel in Borings U-1 and U-3,respectively. <br /> r <br /> 1 <br /> 1 <br /> 3100101/REPORT 1 February 13,1991 <br /> I <br /> 1 <br />