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Mr. Michael Infurna Project 0805-109.01 <br /> October 3, 1994 <br /> Page 2 <br /> features(i.e. station building, storage tanks,dispensers, etc.). If this alternative is selected, <br /> soil removed by excavation cannot be treated on site due to lack of available space and <br /> site constraints; therefore, the soil must be hauled to an appropriate landfill for treatment <br /> and disposal. Additionally, it is not feasible to excavate all petroleum hydrocarbons <br /> impacted due to excavation equipment limitations. <br /> Soil Vapor Extraction. Based on the results of the site assessment and the soil vapor <br /> extraction test (SVET), soil vapor extraction of gasoline hydrocarbons in capillary fringe <br /> soil appears feasible. Implementation of this alternative will require installation of <br /> subgrade piping and installation and operation of a vapor extraction and abatement <br /> system. This method will likely be less disruptive to business operations and is more cost <br /> effective than excavation. <br /> Groundwater Remediation <br /> Groundwater Extraction and Treatment. Based on analytical data collected from <br /> groundwater to date, dissolved gasoline hydrocarbons quantified as gasoline and <br /> halogenated hydrocarbons are present in on-site and off-site wells. Implementation of this <br /> alternative may require the installation of one or more recovery wells. This option will <br /> also require the designing, permitting, and installation of an aboveground groundwater <br /> treatment system. Based on existing concentrations of dissolved hydrocarbons in <br /> groundwater and the excessive amount of water that will be produced to maintain an <br /> effective capture zone, EMCON believes this alternative method is not cost-effective to <br /> remediate groundwater. In addition, based on information gathered at similar sites with <br /> operating groundwater extraction test system, the remediation process is very slow and <br /> target cleanup levels are typically unobtainable. <br /> Air Sparging. As an alternative to conventional groundwater pump and treat and <br /> aboveground treatment, air sparging can be used to provide in situ soil vapor extraction <br /> and air-stripping to remove residual gasoline hydrocarbons from soil and dissolved <br /> hydrocarbons from groundwater. <br /> Air sparging involves injecting pressurized air below the water surface to "strip" dissolved <br /> hydrocarbons from the groundwater to the vadose zone and remove residual hydrocarbons <br /> from the saturated soil. Air bubbles that exit the sparge well move vertically and <br /> horizontally through the saturated soil column "stripping" dissolved hydrocarbons from <br /> groundwater. Hydrocarbon vapors entrained in the air bubbles rise through the saturated <br /> zone into the vadose zone. Control of off-gas in the vadose zone is accomplished using <br /> a conventional vapor extraction system. This alternative method is more cost-effective <br /> than groundwater extraction and treatment. <br /> SAC/pift805\08051090.1cs-94 pas:4 <br />