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r small rates will produce enough drawdown,to create a large capture zone. Groundwater wells <br /> in the area are all screened well below the A and B Zones because of the low yield of these <br /> formations. <br /> Comparison of Remedial Options <br /> The present AS/SVE system is rapidly removing gasoline from the smear zone that is <br /> considered the source of contamination. Treatment options to be summarized in this section <br /> are for the removal of dissolved-phase gasoline in the groundwater plume. Source removal is <br /> well underway. The two options described and evaluated herein are Option A, Intrinsic <br /> Bioremediation.Demonstration, and Option B, Pumping with Aboveground Treatment. <br /> The two groundwater remediation options were evaluated by considering the following <br /> criteria: <br /> 1 <br /> • Overall Protection of Human Health and the Environment <br /> 0 Reduction of Toxicity, Mobility, and Contaminant Mass or Volume <br /> • Short-Term Effectiveness (ability to demonstrate initial progress) <br /> 0 Long-Term Effectiveness (reliability) <br /> • Implementation (technical and administrative feasibility) <br /> • Cost Effectiveness <br /> Both options are expected to provide human health and environmental protection and to <br /> remove contamination. The issues that differentiate these options are long-term effectiveness, <br /> implementation (administrative feasibility), and cost effectiveness. <br /> There are limitations to conventional pump and treat remediation. It can be effective for <br /> 1 removing floating NAPL or intercepting a rapidly migrating plume. The present <br /> ' hydrogeological conditions at the Disco site do not warrant the level of intervention <br /> associated with Option B. Further, Option B would require many permits and approvals that <br /> would delay cleanup and tax valuable administrative resources. Finally, the total cost of an <br /> . intrinsic bioremediation demonstration is less than half the cost of pumping with <br /> aboveground treatment when annual operation and maintenance costs or total net present <br /> worth are compared. <br /> Option A, Intrinsic Bioremediation Demonstration, which is evaluated in Section 4, is highly <br /> recommended over the next best alternative, Option B, Groundwater Pumping with <br /> Aboveground Treatment. Option A includes the following components. <br /> • Continued operation of the AS/SVE system for source removal <br /> 1 • Demonstration of intrinsic remediation <br /> • Groundwater monitoring <br /> • Contingency pian for evaluating monitoring data and determining the need for <br /> intervention <br /> ti- <br /> 5F010030991.DOC ES-2 <br />