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i <br /> Soil flushing is also used in conjunction with ground-water extraction and <br /> requires injecting a solution into the soil which extracts the contaminant <br /> from the soil and flushes the contaminants down toward ground water. A <br /> ground-water extraction system is used to capture the ground water. The <br /> extracted ground water is then treated prior to discharge. However, flushing <br />' will compound the ground-water contamination by introducing new <br /> contaminants and possibly spreading the currently localized impact. Due <br /> to the technical uncertainties and the possibility of not providing adequate <br /> remediation, soil flushing is not recommended for this site. <br /> SVE is well documented for remediation of the lighter petroleum <br />' hydrocarbons, particularly those associated with gasoline. Additionally, <br /> using SVE enhances natural biodegradation by increasing oxygen <br /> concentrations in the impacted soil. SVE can be implemented with minimal <br />' impact on current operations occurring at the site. <br /> SVE will also indirectly remediate the petroleum hydrocarbon-impacted <br />' ground water at the site. The reason for this is that, based on the <br /> concentration of petroleum hydrocarbons detected in the ground water (see <br /> Table 3), it is reasonable to assume that the highest concentration of <br />' petroleum hydrocarbons detected are confined to a limited area in the <br /> vicinity of well MW-13. By implementing SVE, petroleum hydrocarbons in <br /> the ground water will be volatilized and extracted from the ground water into <br /> the soil and ultimately into the soil vapor extraction and abatement system. <br /> In addition, as mentioned above, natural biodegradation will be enhanced. <br />' For these reasons, the proposed remediation system for the site involves <br /> installing and operating a SVE system in conjunction with the existing <br /> vacuum gallery. <br /> 1 <br /> 7.1.1 Performance Criteria <br />' EMCON Associates has identified several performance criteria for the SVE <br /> system, including <br /> o The system must be capable of inducing an extraction <br /> vacuum of at least 25 in. wc. . <br /> • The system must be capable of treating soil vapors at a <br /> flow rate of at least 50 cfm. <br /> • The system must be capable of treating soil vapors <br />' containing fuel at 0.1 percent of the LEL at a flow rate of <br /> 50 cfm. <br /> • The system must be capable of obtaining a minimum of <br /> 95 percent destruction efficiency. <br /> pjOlof9010f900020.1 ag 7 - 2 Rev. 0 December 15, 1992 <br />