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�Aw <br /> Working To Restore Nature <br /> zone, where it is collected by vapor-extraction and routed to a vapor-abatement system The <br /> introduction of air into the aquifer also increases the quantity of oxygen available for <br /> ' hydrocarbon consuming biological activity. However, relatively permeable soils are necessary <br /> for air sparging to be effective. As indicated by the soil boring logs, the soil sediment types in <br /> ' the water bearing zone beneath the site are generally not amenable to allowing homogeneous <br /> dispersion of contaminants in the water bearing zone and effectively promote preferential <br /> pathways Equally important, the soil sediment types immediately above the water bearing zone <br /> are almost entirely clays, which are too fine-grained from which to extract vapors thereafter <br /> 1 I <br /> Alternative 3 - Groundwater Extraction and Passive Soil Remediation. <br /> ' This alternative would consist of active remediation of groundwater by pumping from one or <br /> more extraction wells and treating the extracted groundwater. Initiation of a pump and treat <br /> ' groundwater remediation system would include installation of one or more 4-inch minimum <br /> diameter groundwater extraction well(s) and installation of a carbon filtration system for <br /> groundwater treatment. <br /> No active soil remediation would be initiated. TheazY nm source of residual contamination has <br /> P <br /> ' been removed and the remaining contamination exists in fine-grained soil within the zone of <br /> historic saturation at depths greater than 35 feet Residual soil contaminants would be reduced <br /> over time through natural biodegradation processes In addition, a surface asphalt cap could be <br /> ' completed over the site to limit percolation of surface water through the zone of impaction. <br /> ' 8.0 REMEDIATION ALTERNATIVES EVALUATION <br /> Each of the alternatives presented above were evaluated according to the following criteria <br /> ' 1. Level ofP rotection of human health and the environment <br /> ' 2. Reduction of toxicity, mobility and volume of contaminants <br /> 3 Compliance with regulatory guidelines <br /> 4 Cost effectiveness/public benefit <br /> ' S. Short term effectiveness <br /> 6. Long term effectiveness <br /> 7 Implementability <br /> 1_%M8XREP0 %C"0744 DRF 17 <br />