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' 20 January 2005 <br /> AGE-NC Project No 97-0343 <br />' Page 9 of 21 <br />' encountered ground water is not used for drinking or Irrigation, although all ground water in the <br /> State of California Is considered to be of potential beneficial use <br />' Drinking water at and near the site is supplied by municipal water wells The nearest municipal well <br /> is located approximately 3,600 feet northwest (down-gradient) from the site, it has not been <br /> impacted, and based on the lateral extent of contaminated ground water at the site, it is unlikely to <br />' be impacted by ground water from the site Domestic wells are located within 2,000 feet of the site, <br /> but the nearest one (1,250 feet from the site) is also unlikely to be impacted by site ground water <br />' The nearest surface water features to the site is the Stockton Diverting Canal, located <br /> approximately500 feet north of the site It is possible but unlikely that impacted ground water at the <br /> site would represent a significant pollution threat to water Stockton Diverting Canal,based on little <br />' to no detection of COCs in MW-6 north of the former UST area <br />' 9.0. SOIL REMEDIATION ALTERNATIVES <br /> Three methods for remediation of hydrocarbon-impacted soil for the site were evaluated with <br /> consideration of site-specific factors The methods considered included soil vapor extraction, <br /> excavation and natural attenuation <br /> 91 SOIL VAPOR EXTRACTION <br /> ISoil vapor extraction(SVE) is a well-accepted method of treatment for hydrocarbon-impacted soil <br /> and has been used at numerous sites with an excellent rate of success The method is most effective <br /> on volatile hydrocarbons in permeable soil <br />' 911 Principles <br /> For most SVE systems, a vacuum blower is used to enhance volatilization of hydrocarbons in the <br /> vadose(unsaturated)zone and draw the vapor into extraction wells screened within the contaminant <br /> plume The hydrocarbon vapor is drawn from the wells and "treated" in one of several possible <br /> treatment units (carbon canisters, Internal combustion engines, thermal oxidizers and/or catalytic <br /> Ioxidizers) Air Injection wells maybe Installed outside the contaminant plume to Increase air flow <br /> to the extraction unit <br /> IAn internal-combustion(IC) system draws the vapor stream into a carburetor system of the internal- <br /> combustion engine and mixes the vapor with air before undergoing combustion Exhaust gasses <br /> Advanced GeoEnvironmental,Inc <br />