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. 14 November 1995' <br /> AGE-NC Protect No 95-0121 <br />' Page 13 of 20 ` <br /> , t <br /> I <br /> { <br />' r ' temperature and permeability of the soil Theoretically, the radius of influence of the-inoculation well <br /> _ should increase rapidly at first, then gradually decline as the affected volume increases and the <br /> bactena encounter decreasing hydrocarbon concentrations toward the margins of the contaminant <br />' plume Shorter-chain hydrocarborns are typically consumed first and longer-chain hydrocarbons later <br /> Remediation at sites with similar lithologies typically takes between 18 and 36 months , <br /> 6 3 6 FEASIBILITY <br />' No feasibility studies for in-situ bioremediation have been performed at the site However, since <br /> additional subsurface investigation is likely at the site(i e , the installation of soil vapor extraction or <br /> in-situ air sparging wells), soil` samples should be submitted for physicochemical analysis and <br />' microbiological enumeration These analyses will assist in determining the feasibility of in-situ <br /> bioremediation as a secondary soil treatment method <br /> 6 3 7 ESTIMATED COSTS FOR IN-SITU BIOREMEDIATION <br /> r <br /> The cost for in-situ bioremediation will vary, depending upon the volume of inoculant required and <br /> the number of remediation wells to be inoculated Generally, the cost for in-situ bioremediation will <br /> range from$35,000 to $75,000 Weekly and monthly monitoring generally costs between $1,500 to <br /> $5,000 per month, soil probes to monitor bioremediation progress typically averages $3,000 per <br /> quarter Total costs for bioremediation of soil at the subject site will be between $80,000 and <br /> $165,000 <br /> I <br /> 7.0. REMEDIATION OF HYDROCARBON-IMPACTED GROUND WATER' <br /> 7 1 IN-SITU AIR'SPARGING <br /> Air sparging utilizes air!miection to volatilize dissolved hydrocarbons and force hydrocarbon vapors <br /> ` into the vadose zone, where they can be withdrawn by vapor extraction systems `Air'sparging is a <br /> Icommonly conducted concurrently with vapor extraction, , <br /> '7'l 1 PRINCIPLES r <br /> , <br /> In-situ air sparging (IAS) utilizes air infection beneath-the water table to volatilize dissolved <br /> hydrocarbons in ground water and force hydrocarbon vapors into the vadose zone, where they can <br /> be withdrawn by a vapor extraction system 4 <br /> f { 3 <br />