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J. H. KLEiNFELDER & ASSOCIATES <br /> correlation exists for detectin„ 1,2-dichloroethane at ground water <br /> Sampling locations where concentrations of gasoline are high (MW-1 and <br /> MW-Z). However, Unocal Corporation indicates 1,2-dichloroethane is not <br /> present in their gasoline products. Soil samples collected in the <br /> vicinity of the underground waste oil tank have not detected <br /> 1,2-dichloroethane or indications of leaking conditions. The source of <br /> 1,2-dichloroethane is unknown, however it is found in the ground water at <br /> locationz where gasoline concentrations are high. <br /> The apparent source for ground water contamination by hydrocarbon <br /> compounds 3.s the former undo=rground gasoline storage tanks and/or relater <br /> i <br /> underground piping. The Ground Water Iso-Chem Maps (Figures 14 through <br /> 20) provide support for identifying the underground gasoline storage tanks <br /> ( <br /> and/or related undergrourd piping as the sov, ce' for property ground water <br /> contamination. <br /> Migration of gasoline from the vadose zone: soils into the uppermost <br /> water--bearing unit occurred primarily due to the vertical force of gravity <br /> (strong vertical vector) with intermediate (relatively minor horizontal <br /> ` vectors) horizontal deviations du: to variation in geology ;ind variation <br /> w in chemical compound mobility. <br /> Migration of the gasoline plume within the uppermost water-bearing unit <br /> (Zone IV) is controlled primarily by the direction and gradient of ground <br /> water flow (static and dynamic influences), variation of <br /> geology, <br /> variation in persistence of the various detected compounds and by <br /> variation of the mobility of the various detected compounds. .At this <br /> property, the direction of ground water flow, which is south to southwest, <br /> F has had the most significant influence on the migration pattern of this <br /> j plume. This influence can readily be identified from inspection of the <br /> Potentiomet:ic Surface Maps (Figurer 11, 12 and 13) along with the Ground <br /> f <br /> Water Iso-Chem Maps (Figures !4 through 20). <br /> ;A <br /> 53-87-443 29 <br />