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U-Haul#709-50 <br /> Preliminary Site Conceptual Model Blaes Environmental <br /> December 95,2006 <br /> . descriptions However, given the favorable results of the VE/AS test, VE/AS remediation is likely to be <br /> more cost effective than groundwater extraction as a remedial option for this site <br /> 4 S BIOFEASIBILITY LABORATORY RESULTS <br /> Soil samples were analyzed for two types of bacteria heterotrophic microbes (those that utilize only <br /> organic carbon substrates and generally comprise the great majority of bacteria) and hydrocarbon <br /> degrading heterotrophs (the bacteria that are most useful for the bioremediation of organic contaminants) <br /> Depending on various environmental conditions, bacterial density can vary from Iess than 10 colony <br /> forming units per gram (CFU/g) to 10' CFU/g As a general rule, petroleum hydrocarbon degrading <br /> bacteria should comprise at least 10 percent of the total heterotrophic bacteria in soil considered for <br /> bioremediation Hydrocarbon utilizing bacteria were not detected in the soil samples collected at depths of <br /> 30 and 50 feet bgs Additionally, the heterotrophic plate count was non detect 2n the sample collected at <br /> 50 feet bgs and quite low in the sample collected at 30 feet bgs (200 CFU/g) <br /> Based on the results of soil and groundwater sample analysis, bioremediation at the site may not be a <br /> viable remedial method given the current bacterial and nutrient levels This conclusion is based solely on <br /> • the results of samples collected at specific intervals in one soil boring However, given that bacterial <br /> densities are likely not homogeneous across the site and that hydrocarbon degrading bacteria may exist <br /> elsewhere in the subsurface, the implementation of a full-scale bioremediation system may not be as cost <br /> effective or as reliable as VE/AS for this site <br /> Page 21 <br />