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F <br /> h 15, 1988 AGS 8696-3V <br /> tal Cream and Butter Company, Stockton, California <br /> al-column, manual-injection chromatograph with a photo- <br /> ionization detector that is sensitive to concentrations of <br /> hydrocarbon constituents in the range of parts per billion. ' <br /> The analytical equipment quipment used in this survey was housed in the <br /> Applied GeoSystems Mobile Soil Vapor Laboratory, which provides a <br /> clean, temperature-controlled environment. The detection limit <br /> for the chromatograph was set by verifying linearity and peak <br /> resolution with standard gas containing equal concentrations of 2 <br /> a parts per million benzene, toluene, and xylene isomers (BTX) . <br /> Before analyzing vapor samples, the Photovac was calibrated with <br /> a standard gas containing equal concentrations of 20 parts.: per . <br /> million of the same constituent species. <br /> results of the soil vapor survey are measured in parts por <br /> million of hydrocarbon vapor contained in the soil gas. Results <br /> of the Soil Vapor Survey indicated that concentrations of the <br /> three species of chemical constituents (benzene, toluene, and <br /> xylene isomers) that are associated with the higher volatile <br /> phase of gasoline, were non-detectable above the detection limit <br /> of 2 parts per million within the vapor extracted from the soil <br /> eww using the Applied GeoSystems probe. Soil vapor analyses <br /> performed on the none vapor probe locations did not reveal <br /> detectable concentrations of contamination due to gasoline at the <br /> points sampled. <br /> Sincerely, <br /> Applied GeoSystems <br /> Burton 2. Gilpin <br /> Staff Geologist <br /> :J <br /> REFERENCE CITED <br /> Devitt, D. A. , R. B. Evans, W. A. Jury, and T. H. Starks. Soil <br /> Gas Sensing and Mapping of Volatile gEg nics. National Water <br /> 5. : Well Association, Dublin, Ohio, 1987. <br /> 4 <br />