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to be used are motile, and therefore will migrate into and <br /> remediate the "smear" zone. No additional remedial measures <br /> should be necessary for treatment of the "smear" zone. <br /> 4) A biological inventory of the site was made by our <br /> microbiologist during a visit in June. It was his opinion at <br /> that time that the abundant plant growth on and around the <br /> site testified to favorable soil characteristics for growth. <br /> Furthermore, growth requirements for plants are significantly <br /> more stringent than for bacteria. <br /> No bench tests have been performed, but plate counts of <br /> naturally-occurring microbes in the auger returns from the <br /> vadose zone wells on the site have been completed and growth <br /> has been determined to be luxurious. <br /> 5) The auger returns are also being analyzed for other <br /> constituents, including nitrogen, phosphorous and trace <br /> minerals. . The importance of specific soil characteristics <br /> depends upon the particular bioremediation process <br /> (technology) to be employed. Most of the parameters indicated <br /> in your memorandum, if within certain, very wide limits, are <br /> satisfactory for the process to be employed at the Geweke <br /> site. For instance, pH can range from 4 to 9 . 5. EC has little <br /> or no effect unless sodium levels reach greater than 5% on a <br /> weight basis. We do not have specific data on metals toxicity, <br /> but have not experienced high mortality rates at previous <br /> sites where these particular bacteria have been used to <br /> remediate soil contaminated with hydrocarbons, including waste <br /> oil. The bacteria are tolerant to high metal levels. <br /> The bacteria to be used are facultative anaerobe. We are <br /> presently experimenting with blower systems to improve air <br /> flow to the subsurface at in-situ bioremediation sites in <br /> southern California, and have found blowers to be beneficial, <br /> particularly where contamination is deep or the matrix is <br /> fine-grained. In oxygen-deficient environments, bacterial <br /> growth continues normally. <br /> Regarding particle size distributions, drilling results <br /> indicate that silty to pebbly sand volumetrically predominates <br /> over silt and clay within the vadose zone. Microbial migration <br /> rates are high in coarse-grained material and also occur <br /> satisfactorily within fine-grained deposits, but migration <br /> rates depend partly on hydrocarbon concentrations, and rate <br /> data are very limited and site-specific. No porosity <br /> measurements have been made, but unlithified Quaternary sand <br /> normally ranges between 30 and 45% porosity, depending on <br /> sorting and the abundance of fines. <br /> The importance of adsorption/desorption rates is not clear; <br /> microbial degradation of both adsorbed and free-phase <br /> 2 <br />