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Ms Vicki McCartney Project No 8800401A 0201 <br /> October 26, 2004 <br />' Page 8 <br /> FEASIBILITY STUDY <br />' An evaluation of remedial alternatives that have a substantial likelihood to <br /> achieve cleanup of all impacted soils and/or soils and groundwater At a <br /> minimum, two technologies must be evaluated for implementability, cost and <br /> effectiveness <br />' Monitored Natural Attenuation and Degradation <br /> Natural attenuation requires no active corrective action, but relies on the natural process <br />' of diffusion to reduce hydrocarbon/oxygenate concentrations over time Natural <br /> degradation relies on biological and chemical breakdown of hydrocarbons/oxygenates to <br /> 1 reduce concentrations The existing monitoring and sampling program would be useful <br /> in monitoring declining concentration trends Based on the concentration trend graphs <br /> presented in Appendix E, all constituents of concern have declining concentrations <br /> trends, but the rate of decline of certain constituents indicate that all cleanup goals may <br /> not be naturally achieved for up to 20 years Recent significant declines of certain <br /> constituents suggest that cleanup goals may be achieved naturally in a shorter period of <br /> time <br /> r <br /> Cost Up to$380,000 00($19,000 00 per year) <br /> Time Frame Up to 20 years <br /> Advantages ➢ Low annual cost <br />' ➢ Minimal disruption of station operations <br /> ➢ Does not involve the transport or introduction of contaminants to or from <br /> the subsurface <br />�F ➢ Human health and environmental risk is low given that the risk from <br /> concentrations currently present is low <br /> Disadvantages ➢ Would not actively reduce toxicity, mobility, or volume, but relies on the <br />' natural processes of diffusion and degradation to eventually reduce <br /> these factors <br />' N 1sacDP20041Pr11880000401A 4ad doc Shaw Environmental,Inc <br />