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s a - -= -R&IR - z _ S i INTRODUCTION _ t The following report presents the findings of a soil and groundwater investigation performed by Pacific Environmental Group, Inc. (PACIFIC) at UNOCAL Bulk Plant No.0788 located at 8203 East 11th Street in Tracy, California (Photos 1 &2 and Figure 1). Three groundwater monitoring wells were installed on October 24 and 25, 1990, to evaluate the extent of petroleum hydrocarbons in the soil and groundwater in. the vicinity of a subsurface 5,000-gallon transmission fluid tank recently removed from the si±e. This report presents site background information, a regionalgeologic and . R i hydrologic overview, sample collection and analytical procedures, findings, and recommendations. e Background The .above referenced site is an operating bulk plant with two 19,500-gallon and i two 20 000- allon above F g ground hydrocarbon storage tanks located in the wes.Grn portion of the property (Figure 2). The 19,500-gallon tanks contain diesel and super unleaded gasoline, and the 20,000-gallon tanks contain regular leaded gasoline and f. { unleaded gasoll=ne. According to site personnel,these tanks were installed in 1918 to i replace the tanks originally.installed during construction of the facility. A pardafiy buried 5,000-gallon tank was removed from the southwestern portion of the 4 site on December 13 1989. The Pnznary.use,of this tank was for'transulission:flnid storage,but it has also been used to contain heating oil in the past. Details of the exca- k: vation of this tank are described in a PACIFIC letter to UNOCAL dated March 20, 1990, Soil samples were collected from the eastern and western ends of the tank exca- `. vation at a depth of 8 feet below ground.surface:during'tank removal activities. Certi- fied laboratory analysis of these samples,indicated the presence of 17.P arts per m!lllon m' de w p } ies� ,1,12 pPth toluene,and 4.9 ppm ethylberizene in tli"e eastern end of the exca;" " vatiom The transmission fluid tank resided on an underground concrete pad,which was not removed daring excavation.: Groundwater:was observed'in the 'excava#ton'.at a of 6 feet below surface during the December 1989:tank removal:.activity- -------- -- ----- --- -- 3100101/REPORT 1 February 13,1991 {