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C�EARWATER <br /> G R O U P, E N C <br /> unfeasible Clearwater does not recommend this approach as a primary mechanism <br /> for soil remediation at this site <br /> 7 2 3 Soil Vapor Extraction <br /> The soil vapor extraction process involves the removal of hydrocarbon vapor from <br />' soil pore space in the vadose zone by means of a vacuum blower attached to wells to <br /> draw air through the contaminated zone Volatile hydrocarbon constituents are <br /> released from the soil into the air stream and treated at the surface as required SVE <br /> most effectively removes hydrocarbons from the vadose zone in situations where <br /> soil permeability is moderate to high, and where the fraction of less volatile <br /> hydrocarbons is low relative to those that are more volatile Since volatilization is <br /> the primary mechanism by which this method reduces hydrocarbon concentrations, <br /> large volumes of air must be moved through the soil thereby potentially requiring <br /> expensive blower and emissions control equipment <br />' Feasibility test results indicate that soil vapor extraction is a feasible remedial option <br /> for the mitigation of soil contamination Soil permeability is moderate and <br /> Isubstantial volumes of hydrocarbons can be removed by the this technology while <br /> requiring a low number of extraction points to cover the extent of soil <br /> contamination <br /> 7 2 4 Dual-Phase Soil Vapor and Groundwater Extraction <br /> Dual-phase soil vapor and groundwater extraction involves the removal of <br /> hydrocarbons from the vadose zone as described in the section above, but greater <br /> flowrates and thus hydrocarbon removal rates can be achieved by exposing more <br /> well screen to the air stream by concurrently depressing the water table via <br /> pumping This alternative is useful in situations where groundwater remediation <br /> or plume migration control is also needed <br /> Feasibility test results indicate that dual-phase soil vapor and groundwater <br /> extraction does appear to increase air flowrates and radius of influence from well <br /> RW-1 Because it is likely that groundwater extraction will be used at the site to <br /> capture SPH and the dissolved plume, a dual-phase extraction configuration at <br /> selected wells is a feasible approach to increase the effectiveness of soil vapor <br /> extraction with minimal extra costs <br /> 7 2 5 _Evaluation Soil Vapor Treatment Alternatives <br /> If some version of vapor extraction, either solo or dual-phase, is used to remediate <br /> soils beneath the site, treatment of the extracted air stream will be needed before <br /> discharge to the atmosphere Air treatment alternatives evaluated include use of an <br /> internal combustion (IC) engine, vapor-phase granular activated carbon (GAC), <br /> catalytic oxidation, and a thermal oxidation <br />' D-107,PAR/RAP 17 February 21, 1996 <br />