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CLEARWATER <br /> C R O U P, I N C <br /> Results from the air sparging test indicate that air injected into well SW-1 has a <br />' radius of influence of approximately 50 feet at a flow of approximately 10 cfm at a <br /> pressure of 3 psi Air sparging significantly altered groundwater elevations, <br /> gradient, and direction of flow <br /> 7.0 REMEDIAL ACTION PLAN <br /> 7.1 Purpose and Scope <br /> The purpose of proposed remedial action is to effectively capture and remove <br /> contaminants from groundwater and soil Results of feasibility testing are used in <br /> the following sections during evaluation of remedial alternatives Following <br /> evaluation of remedial options, a remedial approach is selected and discussed in <br /> detail <br /> 7.2 Evaluation of Soil Remediation Alternatives <br /> The feasibility of several soil remediation options has been evaluated for their <br /> particular effectiveness and limitations as they apply to this specific site Soil <br /> remediation alternatives considered include passive biodegradation, excavation, soil <br /> vapor extraction, and dual-phase soil vapor extraction with groundwater extraction <br /> 7 2 1 Passive Biodegradation <br /> Passive biodegradation is the remedial mechanism that has been at work in the soil <br /> at this site since petroleum hydrocarbons were introduced into the subsurface <br /> Based on the depth below the surface and the high TPH concentrations in the soil, <br /> passive biodegradation of hydrocarbons in the unsaturated zone would likely <br /> require an excessive amount of time to bring the concentrations of gasoline <br /> hydrocarbons to levels for regulatory compliance Given that a domestic water well <br /> is located within 50 feet of the soil contamination, the ongoing threat of potential <br /> groundwater contamination to shallow groundwater makes this option untenable <br /> Clearwater does not recommend passive biodegradation as the primary remedial <br /> measure selected for the unsaturated zone of contamination <br /> 7 2 2 Excavation <br /> Excavation of contaminated materials is most effective in situations where <br /> hydrocarbon compounds are concentrated mostly in soil (groundwater impact is <br /> minimal), and where the areas of hydrocarbon concentration fall outside of the <br /> primary operating areas of the subject facility Neither is the case at this site The <br /> majority of soil contamination is already intertwined with groundwater <br /> contamination in the "smear zone" extending from approximately 10 to 17 feet <br /> below grade Also, the extent of soil contamination is configured such that <br /> excavation would not only be limited by the locations of structures on-site, but also <br /> jeopardize their stability Considering these technical obstacles, excavation appears <br /> D-107, PAR/RAP 16 February 21, 1996 <br />