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March 18, 1993 <br /> ' Page 8 <br /> o Technical: Alternative 1 was ranked most favorable while <br /> Alternative 2 was ranked least favorable. The point that ranked <br /> Alternative 1 above Alternative 2 was anticipated mass removal <br /> rate. The inclusion of soil vapor extraction(Alternative 1) will <br /> allow removal of hydrocarbon mass at a considerably faster rate <br /> than using just liquid extraction(Alternative 2). Additionally,use <br /> of soil vapor extraction will allow application of air sparging. Air <br /> sparging will contribute to the mass removal rate in two ways. <br /> First, it will facilitate an increase in surface contact between air <br /> and impacted,media; thus increasing mass transfer. Second, it <br /> will increase the supply of dissolved oxygen available for <br /> biodegradation. Other superior qualities associated with <br /> Alternative 1 include: spatial selectivity in application, little . <br /> potential for enhancement of residual hydrocarbon migration <br /> from potential off-site sources, and ease of treatment for <br /> extracted vapor versus groundwater. <br /> o Institutional: Both alternatives can achieve institutional <br /> requirements as outlined in CCR,Title 23, Article 11 and applica- <br /> tion of either alternative will similarly affect the community. <br /> Treated fluid discharge permitting and permit compliance will be <br /> more complex for.Altemative 2. <br /> o Environmental Protection: Both alternatives provide a high <br /> degree of environmental protection. Alternatives were ranked <br /> equally considering environmental protection. <br /> o Economic: Alternative 2 will require a lower capital influx than <br /> Alternative 1, and operation and maintenance costs will be <br /> slightly lower than those expected for Alternative 1. However, <br /> soil vapor extraction(Alternative 1)will require less time to <br /> reduce hydrocarbon mass beneath the site than liquid extraction <br /> (Alternative 2). Based on economic analysis, alternatives were <br /> ranked from most economical to least economical. Considering a <br /> 5-year soil vapor extraction lifespan and at least a 10-year liquid <br /> extraction lifespan, alternatives were found to be economically <br /> .equivalent within the range of estimation error (+/-30 percent). <br /> Alternative lifespan was based on anticipated removal rate. On <br /> average, the removal rate using soil vapor extraction is two orders <br /> of magnitude greater than that for liquid-phase extraction. <br /> 3100104/TRAP <br />