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EXECUTM SUMMARY This report has been prepared by Pacific Environmental Group, Inc. (PACIFIC) to document the findings of a soil and groundwater investigation performed at UNOCAL Bulk Plant No.0788 located at 8203 East 11th Street in Tracy,California. A summary of investigative findings is presented below: o A partially buried 5,000-gallon transmission fluid storage tank was removed from the southeastern portion of the site on December 13, 1989.. Analytical results indicated that low levels of petroleum hydrocarbons remained in the soils adjacent to the excavation. o The San Joaquin County Public Health Services Department issued an "Unauthorized Storage Tank Release/Contamination Site Report" on January 30, 1990,and requested additional investigation. o 'PACIFIC installed.three groundwater monitoring wells (U-1 through s U-3)on October 24 and 25, 1990. 3 } o The site is underlain by primarily fine grained deposits (silts and clays) to the total depth explored of 27 feet. Sands were observed in each of the borings at depths of approximately 17 to 25-1/2 feet below ground d surface with thicknesses ranging from 1-1/2 to 5 feet. o Static groundwater occurred at a depth of approximately 9-1/2 feet below grade during November 1990 with a calculated north- northwesterly gradient of 0.006. 3 o Selected soil samples were analyzed for TPH gasoline, TPH diesel, I halogenated volatile organics (EPA 8010), and benzene, toluene, ethylbenzene, and total xylenes (BTEX compounds). The hydrocarbon concentrations range from ND to 1,800 parts per million (ppm)TPH gasoline, and from ND.to 710 ppm TPH diesel at the 5 to 6-1/2.foot interval. The concentrations attenuate to non-detectable levels at the 10 to I1-1/2 foot interval with the exception of 3.2 and 5.2 ppm TPH diesel in Borings U-1 and U-3,respectively. 3100101/REP0RT 1 February 13,1991 _