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ts:y <br /> i <br /> Chevron U.S.A. <br /> ' Page 17 <br /> 6.0 ANALYSIS OF REMEDIAL EFFORT <br /> The purpose of the remedial effort was to reduce the <br /> potential for migration of contaminants. Migration of <br /> s. <br /> gasoline related contaminants in soil occurs via three main <br /> processes: hydraulic head induced flow (from surface water <br /> infiltration or a continuous point source leak) , advection in <br /> �. downward migrating water, and vapor phase diffusion. Since <br /> the point source of contamination, the dispenser islands, <br /> Y have been removed, contaminant transport mechanisms are <br /> c� limited to infiltrated surface water induced migration and <br /> y vapor phase migration. The remedial method employed at the <br /> site will tend to reduce the potential for migration in a <br /> two-fold manner. First, the removal and treatment of <br /> { <br /> contaminated soil removes the source of hydrocarbons for <br /> I <br /> vapor, dissolved constituent advection, and downward flow of <br /> residual product. Secondly, the replacement of clean and <br /> ` ._ treated soil as an engineered fill will tend to reduce the <br /> - potential for surface water infiltration. <br /> The removal of contaminated soils was accomplished by <br /> excavation, and treatment by aeration of the soil. Chemical <br /> analyses performed on samples taken from the limits of the <br /> •- excavation revealed that only fractional levels of gasoline <br /> -,� <br /> related <br /> -petroleum-was-present.---The-results-of-analyses------------------- <br /> 16000-250-044 <br /> analyses-- -16000-250-044 <br /> �. Corrected <br /> DA\IF;S t 1fooijL <br />