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i <br /> I <br /> i <br /> 15 February 2000 <br /> AGE-NC Project No 98-0448 <br /> Page 21 of 33 <br /> i <br /> per well can be used to enhance oxygen concentrations during the process <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 /> 8 3 3 Inoculation Wells <br /> The effective radius of influence of inoculation wells Is generally 15 to 20 feet Existing monitoring <br /> wells can be used for inoculation of ground water and the smear zone A greater radius of influence <br />' <br /> is usually obtained for ground water inoculation, since ground water movement can assist the <br /> bacterial migration However, temporary or additional permanent inoculation points may be needed <br /> to adequately address the vadose zone <br /> 8 3 4 Monitoring Activities <br /> The inoculation wells and ground water monitoring wells should be monitored for several months <br /> after initial inoculation by collecting periodic field measurements of organic vapor, carbon dioxide, <br /> and oxygen concentrations Quarterly or semi-annual monitoring activities should include the <br /> installation of soil borings to collect soil samples to monitor bacterial populations, nutrient <br /> availability and soil remediation progress If momtonng indicates areas of slow remediation, <br /> additional inoculations may be required <br /> 8 3 5 Duration <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 encounter decreasing hydrocarbon concentrations toward <br /> the margins of the hydrocarbon plume Shorter-chain hydrocarbons are typically consumed first and <br /> longer-chain hydrocarbons later Based upon the above mentioned factors, a duration of 18 to 36 ' <br /> months Is estimated for successful in-situ bioremediation <br /> Advanced GeoEm i ronmental,Inc <br />