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1 <br /> 4 EVALUATION OF REMEDIAL ALTERNATIVES <br /> As directed by the SJCPHS in a letter received in December 2000endix A an evaluation <br /> 2000 (Appendix A)� <br /> of"other remedial alternatives for groundwater cleanup" was conducted to address current site <br /> conditions The screening criteria for remedial alternative development are presented below <br /> 4.1 SCREENING CRITERIA FOR REMEDIAL ALTERNATIVE DEVELOPMENT <br />' The selection of appropriate remedial alternatives for hydrocarbons and MTBE at the i <br /> y site s <br />' based on evaluation of the following criteria <br /> • Reduction of Toxicity, Mobility, and Volume. This criterion establishes preference for an <br /> 1 alternative that will produce permanent, significant reductions The evaluation focuses on <br /> the amount of chemicals to be destroyed or treated, the effectiveness of the treatment, and the <br /> type and quantity of residual chemicals that will remain after treatment <br />` • Technical Feasibility Technical feasibility refers to the possibility of construction given <br /> site constraints, reliability of the technology, and the ability to monitor the effectiveness of an <br /> alternative Each alternative requires evaluation against site-specific hydrogeologic and soil <br /> conditions <br />�. • Cost This criterion is used to assess capital and operation and maintenance (O&M) costs on <br /> a conceptual level only Capital costs include direct costs, such as equipment, and site <br /> construction/development Indirect costs include engineering, permitting, and startup costs <br /> O&M costs include ongoing labor, materials, repairs, administrative fees, and reporting costs <br /> during the operating period <br /> 4.2 DEVELOPMENT OF CORRECTIVE ACTION ALTERNATIVES <br /> The following remedial options were evaluated to address current site conditions <br />' • Air Sparging. Air sparging technology has been used at the site to supplement the vapor <br /> extraction system as described in Section 2 3 The contribution of air sparging to the <br /> effectiveness of the former vapor extraction system would be difficult to determine <br /> However, the heterogeneity of the saturated zone at the site would make offgas control from <br /> a larger air sparging system difficult <br /> • Slurry Wall. Land use at the site and in the downgradient area present practical limitations <br /> and increased expense to a slurry wall installed via trenching A slurry wall created by <br /> infection from the surface would require a large amount of injection points to intercept <br /> hydrocarbon migration An effective in situ barrier has not been documented for this <br /> application <br /> • Interception Trench The same practical limitations of land use apply for an interception <br /> trench as they do for installation of a slurry wall via trenching For effective source <br /> reduction, a trench would need to be installed near the former UST locations To effectively <br /> 6 1Puojecls�739421MAS7ER%WP\RzOHOI%text2 doe 7 <br />