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05 May 1997 <br /> AGE-NC Project No 95-0173 <br />' Page 18 of 29 <br />' 7 3 5 Duration <br /> Duration (and cost) of rn-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 Remediation at sites with similar soil compositions typically takes <br />' between 18 and 36 months <br />' 7 3 6 Feasibility <br /> In-situ bioremediation of hydrocarbon-impacted soil at the site has a low feasibility at the site <br /> tMicrobial enumeration and physicochemical laboratory analysis of soil samples collected at the site <br /> indicated that selected microbial enumeration (hydrocarbon degrading organisms) were detected at <br /> 400 CFU (colony forming units) per gram The laboratory indicated that these physicochemical <br /> lie conditions at the site were inadequate to support microbial growth and bioremedial activity The <br /> analysis also indicated that a degree ofbiotoxicity to the microbes may be present at the site,possibly <br /> due to agents such as heavy metals in the soil or to excessive concentrations of gasoline constituents <br /> Furthermore,additional nutrients may be required to replace those consumed during remediation due <br /> to the high concentrations of remaining petroleum hydrocarbons at the site Laboratory analysis of <br /> tnitrate-nitrogen indicated low levels inadequate to support biodegradation <br />' 7 3 7 Estimated Cost For In-Situ Bioremediation <br /> The cost for in-situ bioremediation will vary, depending upon the volume of inoculant required, the <br />' number of remediation wells to be inoculated and the duration of bioremedial activity Generally, <br /> the initiation cost for in-situ bioremediation will range from $35,000 to $75,000 Furthermore, <br /> weekly and monthly monitoring generally costs between $10,000 to $20,000 annually, soil probings <br /> to mnnitnr binrPmPriintinn nrnal'PCC typically nvPrnaPC 0.5 000 to V 0,000 annually <br /> 7 4 NATURAL ATTENUATION <br />' Natural attenuation, or passive bioremediation, is a remedial alternative that relies on natural <br /> processes to degrade hydrocarbons Natural attenuation is not an"inactive"remediation method and <br /> . does require specific characterization and long-term monitoring <br /> Advanced GcaEnvsronmentai,Inc <br /> 1 <br />