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a - <br /> 4 <br /> 1 <br /> R. <br /> N <br /> �. March 15, 1988 AGS 8696--3V <br /> crystal Cream and Butter company, Stockton, California <br /> 0 <br /> SOIL VAPOR SURVEY <br /> Background and Purpose <br /> A geologist from Applied GeoSystems was present at the subject <br /> site on January 13, 1988 to conduct a soil survey to evaluate <br /> possible subsurface hydrocarbon contamination. Field work <br /> included use of the Applied GeoSystems Mobile Soil vapor <br /> Laboratory to collect and analyze soil vapor at nine sampling <br /> locations. <br /> The purpose of this soil vapor survey was to evaluate the extent <br /> of detectable hydrocarbon vapor in the soil. The relative <br /> concentrations and the lateral extent of hydrocarbon <br /> contamination as vapor in soil has been found to correlate to <br /> that in ground water (Devitt, et al. , 1987) ; therefore, a soil <br /> vapor survey may be used to help evaluate the lateral extent of <br /> hydrocarbon contamination in both the soil and ground water.. <br /> Soil Vapor <br /> Application of the soil vapor survey is based on the tendency of <br /> hydrocarbons to volatilize and migrate through the pore spaces of <br /> soil. Hydrocarbon product can migrate through the subsurface as <br /> free product or as dissolved product in water. Each may act as a <br /> source o�" hydrocarbon vapor in the soil pores. In addition, <br /> residual product bound by tensional forces within pore spaces act <br /> as a source of hydrocarbon vapor. variables that influence <br /> hydrocarbon movement in the soil include the physica; and <br /> chemical properties of the organic contaminants, properties of <br /> the unsaturated zone, and the hydrogeologic properties of the <br /> site. Site-specific parameters may include the vapor pressure, <br /> water solubility, and concentration of the chemical; the <br /> ' porosity, moisture content, and organic content of the site soil; <br /> and the direction and velocity of the ground water. <br /> Vapor Survey Equipment and Sampling Procedure <br /> Equipment used to sample soil vapor included a hardened steel <br /> drive-tip, a down--hole sampling assembly with vacuum vials, steel <br /> probe rods with an outside diameter (O.D.) of 1.75 inches, and a <br /> driving unit. The probe rod and tip were hydraulically pushed or <br /> drivan to a pre-determined depth at which point the drive-tip was <br /> openedanda-soil vapor sample was recovered. <br /> 2 <br /> `' AR,016e0f GeoSystems <br />