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a <br /> KEI-J92-0205.R4 <br /> . July 6, 1994 <br /> Page 7 <br /> Based on the analytical results of the final soil samples that <br /> were collected during the removal of the underground storage <br /> tanks, it appears that the majority of the contaminated soil <br /> in the vicinity of the former tank pit has been removed. <br /> Therefore, soil contamination due to underground storage tank <br /> operations at the former Unocal site has been remediated. <br /> 2 . Soil Contamination Removal and Dis osal <br /> Approximately 230 cubic yards of soil were excavated from the <br /> underground storage tank pit to a maximum depth of 10 feet <br /> below grade. This soil was subsequently sampled, analyzed, <br /> and removed from the site. On November 16, 1992 , the exca- <br /> vated soil was shipped to BFI Waste Systems in Livermore, <br /> California (an approved Class III landfill) , by Dillard <br /> Trucking of Byron, California. An additional 120 cubic yards <br /> of soil were excavated from the southeast sidewall of the <br /> underground storage tank pit to a maximum depth of 10.75 feet <br /> below grade. This soil was also sampled, analyzed, and <br /> removed from the site on May 21, 1993, by Dillard Trucking of <br /> Byron, California. The landfill accepting this soil was <br /> Forward, Inc. , of Stockton, California (an approved Class III <br /> facility) . <br /> 3 . Ground Water Contamination Delineation <br /> Based on the analytical results of the ground water samples <br /> collected and evaluated to date (the results that are avail- <br /> able to KEI, Tables 2 and 3) , the following conclusions can be <br /> drawn: <br /> a. The residual petroleum contamination periodically detected <br /> in Unocal well MW3 is most likely the result of the <br /> operations at adjacent sites. Unocal well MW3 is side <br /> gradient (and at times, upgradient) from the former Unocal <br /> underground storage tank locations, and downgradient from <br /> the adjacent site operations. <br /> b. The chlorinated solvent and petroleum hydrocarbon contami- <br /> nation in Unocal well MW5 is likely caused by the opera- <br /> tions at other adjacent terminals and not by the operation <br /> of Unocal' s former underground storage tanks. Well MW5 is <br /> close to piezometers P14 and P15 (Figure 1) , and also <br /> close to additional monitoring wells that have been <br /> installed at adjacent sites, but is quite distant from the <br /> former Unocal underground storage tank locations. In <br /> addition, 1-2-dichloroethane was detected only in Unocal <br /> . well MW5 and not in the other Unocal monitoring wells. <br /> Based on this information, it appears that the dissolved <br />