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December 27, 1995 <br /> Page 4 v <br /> �. May 12, 1989) A subsequent vacuum radius of influence analysis was conducted using <br /> Well MW-4, the estimated effective radius was 112 feet (EA, March 25, 1991) A <br /> conservative SVE radius of influence of 20 feet was used to determine spacing of new <br /> SVE wells (Figure b) � <br /> Air Sparging Design Basis <br /> The effective radius of influence of sparge wells is highly variable and dependent on <br /> several factors Based on previous experience and a review of published studies it is <br /> estimated that the radius of influence of sparge wells will be approximately 25 feet <br /> Additional influence will be achieved by the transport of dissolved oxygen to <br /> downgradient wells Two new sparge wells are proposed for the remediation system and <br /> are constructed of 2-inch diameter PVC casing, completed to a depth of 50 feet _ <br /> Proposed sparge well spacings for new Wells S-1 and S-2 are based on an expected <br /> radius of influence of 25 feet As with the SVE well placement, this is a conservative <br /> estimate <br /> Enhanced Biodegradation <br /> Upon conclusion of SVE, a biodegradation assessment will be performed at the site as a <br /> first step towards determining hydrocarbon biodegradation occurrence in soil and <br /> . groundwater The baseline biodegradation assessment will consist of measuring several <br /> parameters in the saturated and vadose zones In the saturated zone, groundwater will <br /> be analyzed for concentrations of dissolved oxygen, dissolved nutrients (nitrate, phos- <br /> phate, and sulfate), and dissolved hydrocarbons In the vadose zone, the assessment <br /> consists of analyzing soil gas for concentrations of oxygen, carbon dioxide, and <br /> hydrocarbon vapors Test results will be reviewed to determine whether aerobic and/or <br /> anaerobic biodegradation of hydrocarbons is occurring beneath the site <br /> Biodegradation will be relied upon to address downgradient capillary fringe impact To <br /> enhance biodegradation, the availability of subsurface oxygen will be increased through <br /> low flow air infection into Well S-1 Throughout SVE system operation, biodegradation <br /> assessment data will continue to be collected Upon conclusion of SVE, additional <br /> biodegradation assessment data will be reviewed and the applicability of other biodegra- <br /> dation based technologies will be determined to address possible residual on-site hydro- <br /> carbon impact (e g , low flow air injection, ORC, or hydrogen peroxide infection) <br /> DESIGN PRESENTATION <br /> Tasks required to implement the proposed remedial design are presented below Tasks <br /> include a general system design, permitting, construction, system start-up, operational <br /> data collection, and reporting - <br /> i <br /> 3201333BIWRKPLH3 <br />