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App/!Ed >�7E0.�3y5fG'/I7S_ __ i191•E Yuwer Inn flood, Sacramento,CA 95&26 (9161-152-:901 <br /> • FREMONT •COSTA MESA m SACRNMENTO s HOUSTON <br /> July 8, 1988 <br /> 070STROS <br /> AGS Job No. 38032-2 <br /> t <br /> Mr. Tim Ross <br /> �y UNOCAL Corporation <br /> 2175 North California Boulevard <br /> Suite 650 <br /> Walnut Creek, California 94596 <br /> Subject: Executive summary of Work Plan for evaluation of soil <br /> and ground-water contamination at UNOCAL Service <br /> Station No. 6981, 4707 Pacific Avenue, Stockton, <br /> California. <br /> Mr. Ross: <br /> - The enclosed Work Plan describes a program designed to evaluate <br /> the vertical and horizontal extent of hydrocarbon contamination <br /> at the above-referenced site. During installation of a gasoline-- <br /> blending system by UNOCAL Corporation, Applied GeoSystems was <br /> contracted to collect native soil samples from locations <br /> specified by UNOCAL personnel. Results of the sail analyses <br /> indicate that the soil was contaminated with hydrocarbons. Rased <br /> on these findings; Applied GeoSystems observed further excavation <br /> which revealed contamination present to an approximate depth of <br /> 20 feet. Contaminated soil was excavated to a depth of <br /> approximately 20 feet in areas not limited by site structures. <br /> UNOCAL Corporation subsequently removed three underground <br /> gasoline storage tznks from the site. Analyses of soil samples <br /> collected beneath she former tanks indicated contamination of the <br /> soil. In response to these results, the tank cavity was <br /> excavated further to a maximum of approx4=ately 22 ;deet below <br /> grade. Results of soil samples obtained from the limits of the <br /> excavation indicate that soil contamination remains in the center <br /> and northeast portions of the tank cavity. <br /> Based on the presence of hydrocarbon contamination encountered, <br /> Applied GeoSystems recommended further work at the site. This <br /> work should include delineation of the vertical and horizontal <br /> extent of possible ground-water contamination. We recommend <br />