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I <br /> 16 August 2001 <br /> AGE-NC Project No 97-0312 <br /> Page`10 of 20 <br /> hydrocarbons The bactena are microaerophilic and facultatively anaerobic, and therefore abundant <br />' oxygen is not necessary for the process to occur Exotic forms of oxygen(such as hydrogen peroxide <br /> _ or liquid oxygen) are usually not required However, free oxygen does increase the metabolic rates <br />' of the bacteria A small blower delivering atmospheric air to the subsurface at a rate of two to five <br /> scfin per well can be used to enhance oxygen concentrations dunng the process <br /> 4 I <br /> I f <br />' The bacteria are tolerant to a wide range of soil conditions For instance,pH can range from 4 to 9 5 <br /> and electrical conductivity has little or no effect on bacterial metabolism unless sodium <br /> concentrations exceed 5% on a weight basis <br /> I I , <br /> 7 2 3 Inoculation Wells <br />' The effective radius of influence of inoculation wells isenerall 15 to 20 feet, but may vary <br /> g Y <br /> significantly depending on soil composition Existing monitoring wells can be used for inoculation <br />' of ground water and the smear zone A greater radius of influence is usually obtained for ground <br /> water inoculation, since ground water movement can assist the bacterial migration Temporary or <br /> additional permanent inoculation points may be needed to adequately address the vadose zone <br /> I 7 <br />' 7 2 4 Monitonng Activities <br /> The inoculdtion wells chill grOLLIO water monitoring wells should bv, monito-tod fol several ilioliiiL� <br /> after initial inoculation by collecting periodic field measurements of organic vapor,carbon dioxide, <br /> and oxygen concentrations Confirmation soil borings are necessary on a quarterly or semi-annual <br /> basis to monitor bacterial populations, nutrient availability and soil remediation progress If <br />' monitoring indicates areas of slow=remediation, additional inoculations may be required <br /> y ' I <br /> I <br /> I ) H <br /> 7 2 5 Duration <br /> ;I t <br /> Duration (and cost) of in-situ bioremediation are dependent'on the volume of soil and water to be <br />' remediated, the number of, inoculation and monitoring wells, the average concentrations of <br /> contaminants and nutrients, temperature and the permeability of soil Theoretically, the radius of <br /> influence of the inoculation well should'increase 'rapidly at first, then gradually decline as the <br />' affected volume increases and the bacteria ericounter decreasing hydrocarbon concentrations toward <br /> the margins of the hydrocarbon plume Shorter-chain hydrocarbons are typically consumed first and <br /> longer-chain hydrocarbons later A duration of 36 to 48 months is estimated for successful in-situ <br />' bioremediation <br /> F r <br /> t i <br /> Advanced GeoEnvsronmental,Inc <br /> I <br /> r I 4 <br /> I , I <br />