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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.078$located at 8203 East lith Street in Tracy, California. A summary <br /> of investigative findings is presented below: <br /> l <br /> o A partially buried 5,000-gallon transmission Iluid storage tank:was <br /> i <br /> zemoved`from the southeastern portion of the site on-December-1 ., <br /> .1989. Analytical results indicated that Iow levels of petroleum <br /> hydrocarbons remained in the soils adjacent to the excavation. <br /> o The San Joaquin County Public Health Services Department issued an a <br /> "Unauthorized Storage Tank Release/Contamination Site Report" on <br /> January 30, 1990,and requested additional investigation. <br /> ~' o PACIFIC iristalled`:three groundwater monitonng wells (U-1 through <br /> . <br /> R U-3)on October 24 and 25, 1990. ' <br /> r 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 /> i 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 /> o Static'groundwater'occurred at a depth';,of approximately.9 1/2 feet r <br /> below grade during November 1990 with a calculated north- <br /> northwesterly gradient of 0.006. <br /> t o Selected soil samples were analyzed for TPH gasoline, TPH diesel, <br /> halogenated volatile organics (EPA 8010), and benzene, toluene, s <br /> ethylbenzene, and total xylenes (BTEX compounds). The r <br /> 'hydrocarbon'concentrations:range from ND to 1,800 parts per'million., 4 <br /> (ppm)TPH gasohne,,and from ND.to 710,ppm;TPH diesel at:the.5 to' <br /> r .6-1/2.foot interval: The concentrations attenuate 410 1. non-detectable <br /> levels at the 10 to 11-1/2 foot interval with the exception of 3.2 and <br /> 5.2 ppm TPH diesel in Borings U-1 and U-3,respectively. <br /> 1 February 13,1991 <br /> 3100101/REPORT <br /> s <br /> r <br />