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• Disadvantages This method has not gained wide acceptance as a remedial alternative <br /> The relatively low air flows when compared to SVE result in low air exchange rates to <br /> the subsurface and available oxygen may be utilized at the margins of the <br /> petroleum-impacted soil The relatively low permeability of the silts and clays present <br /> within the vadose zone would inhibit migration of air though the soil column. <br /> Installation of bioventtng wells would be required. With the anticipated low radius of <br /> influence, numerous venting wells would be required Installation of wellhead equipment <br /> provides an aboveground obstruction <br /> Anticipated Cost and Time _Frame The anticipated time frame is approximately <br /> 6 months to 1 year to assess the practicality of passive bioventtng and an additional 1 to <br /> 3 years to remediate the site Anticipated cost of implementation range from $20,000 to <br /> $40,000 <br /> Groundwater Extraction and Treatment <br /> Advantage This approach removes the dissolved contaminant, to this case diesel <br /> Diesel may not be efficiently removed by AS and SVE because of the low volatility <br /> Disadvantages_ Tlus is a generally high-cost alternative and is labor intensive with <br /> operation and maintenance (O&M) of a groundwater treatment system High <br /> . concentrations of dissolved metals can foul the system and reduce efficiency The <br /> generally poor water quality to the site area contains high concentrations of metals and <br /> TDS <br /> Anticipated Cost and Time Frame The anticipated time frame to remove the TPHD <br /> plume may be on the order of 5 to 10 years Anticipated costs would include extraction <br /> well and system installation, O&M, carbon, costs, and discharge permit costs These <br /> costs may range from $100,000 to $300,000 depending on equipment selected and O&M <br /> requirements <br /> High Temperature Thermal Desorption <br /> Advantages_ The heated air stream will be more effective to removing diesel impacts <br /> than AS with unheated air This approach, if conducted with spargtng, using heated air <br /> would address groundwater impacts <br /> Dtsadva�4es This is a generally high-cost alternative and high-utility usage would be <br /> incurred. The method is not well established for groundwater remediation Infection of <br /> hot air into the water-beanng zone may lead to precipitation of metals to the infection <br /> wells <br /> SAON\PJ212794127941000 IGS-981cbell 8 Mon <br /> E-5 Rev 0,8!5198 <br />