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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 /> 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 /> have been removed, contaminant transport mechanisms are <br /> limited to infiltrated surface water induced migration and <br /> 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 /> contaminated soil removes the source of hydrocarbons for i <br /> vapor, dissolved constituent advection, and downward flow of ' <br /> 1 <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 /> e <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 /> related petroleum was present. The results of analyses <br /> 16000--250--044 <br /> Corrected <br /> Doti, & \�IOORL <br />