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20 March 1996 AGE-NC Project No 95-0130 Page 15 of 23 ' several months by periodic field measurements of organic vapors, carbon dioxide, and oxygen Ground water samples should be collected and analyzed for petroleum hydrocarbons to monitor ' progress of the remediation Quarterly monitoring activities should include the installation of soil borings to monitor bacterial populations, nutrient availability and soil remediation progress If monitoring indicates areas of slow remediation, additional inoculations may be required I ' 6 3 5 DURATION Duration and cost are dependent on the volume of soil to be remediated, the number of inoculation and monitoring wells and events, the average concentrations of contaminants and nutrients, and the temperature and permeability of the soil Theoretically, the rate of expansion of the radius of bacteria- affected soil around the inoculation wells should increase rapidly at first, then gradually decline as the ' affected soil volume increases and the bacteria encounter decreasing hydrocarbon concentrations toward the margins of the contaminant plume Shorter-chain hydrocarbons are typically consumed first and longer-chain hydrocarbons later Based upon the lithology and hydrocarbon concentrations, in-situ bioremediation at the TFS site could be completed within 24 to 36 months 6 3 6 FEASIBILITY Based upon results of analysis of soil samples, additional subsurface investigation and analysis would be required to adequately implement an in-situ bioremediation system at the TFS site Biotoxic conditions exist in some areas at the site, requiring investigation of localized areas of the site for the presence of heavy metals or high salts The addition of several important nutrients, such as oxidized and reduced nitrogen, would be necessary to sustain microbial growth at the site I Based upon presently available information concerning specific site conditions and the results of physicochemical analysis and microbiological enumeration, it appears that in-situ bioremediation as a soil treatment method would have hnuted applicability at the TFS site 6 3 7 ESTIMATED COSTS FOR IN-SITU BIOREMEDIATION The cost for in-situ bioremediation will vary, depending upon the volume of inoculant required and the number of remediation wells to be inoculated For the TFS site, estimated costs for implementation of an in-situ bioremediation system will range from $100,000 to $150,000 Weekly and monthly monitoring costs generally range between $1,500 to $5,000 per month, soil probe sampling to monitor bioremediation progress typically averages $3,000 per quarter Therefore, if feasible, total costs for bioremediation of soil at the subject site will be between $175,000 and $300,000