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Report on Soil and Ground-Water Evaluation September 11, 1989 <br /> Proposed ARCO Station, Woodbridge, California AGS 39044-1 <br /> Soil-Vapor Survey <br /> The purpose of the soil-vapor survey was to evaluate the extent of detectable hydrocarbon <br /> vapor in the soil. The relative- concentrations and the lateral extent of hydrocarbon <br /> contamination as-vapor in soil have been found to correlate with those of ground.water <br /> (Devitt, et al., 1987); therefore, a soil-vapor survey can be used-to evaluate qualitatively the <br /> lateral extent of-hydrocarbon contamination in _both the soil=and ground water. Application <br />*W of the soil-vapor survey is based on the tendency of hydrocarbons with low molecular <br /> weights to volatilize and migrate through the pore spaces of soil. Volatile hydrocarbons can <br /> migrate through .the subsurface as free product or as dissolved product in water, and <br /> thereby act as a source of hydrocarbon vapor in the soil pores. Residual product trapped <br /> or bound within pore spaces also acts as a source of hydrocarbon vapor. Variables <br /> influencing hydrocarbon movement in the soil include the physical and chemical properties <br /> of organic contaminants, properties of the unsaturated zone, and hydrogeologic properties <br /> in the subsurface at the site. Site-specific parameters may include vapor pressure, water._ <br /> solubility, concentration of the chemical-, porosity, and moisture content of the site;soil. <br /> Vapor Survey Equipment and Sampling Procedure <br /> A geologist from Applied GeoSystems was at-the site on June 9, 1989, to conduct the soil- <br /> vapor survey. Field work included use of Applied GeoSystems' Mobile Soil-Vapor <br /> 7 -- <br /> A)0)01%901 <br /> App1%901 GeoSystems <br />