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27 December 1996 <br /> AGE-NC Project No 95-0143 <br />' Page 17 of 19 <br /> 6 3 4 FEASIBILITY STUDIES <br /> Results of the bioremediation pilot tests at other sites indicate that lighter petroleum hydrocarbons, <br />' such as gasoline compounds are biodegraded more readily than longer-chain(heavier)hydrocarbons, <br /> such as diesel fuel compounds Feasibility studies have not been performed at the subject site <br /> I6 3 5 DURATION <br /> Cleanup durations for in-situ bioremediation will vary, depending upon specific site characteristics <br /> However, an 18 to 36 month treatment period is generally achievable Since dissolved hydrocarbon <br /> concentrations at the site are high, a cleanup period of 36 months is likely <br /> I <br /> 6 3 6 COST <br /> I Bioremediation of round water can be a very cost-effective meth <br /> g rY ad of treatment With little on-site <br /> equipment required beyond the initial inoculation, the cost for m-situ bioremediation at the Chase <br /> Chevrolet - Van Buren site would be between $70,000 00 and $100,000 00 However monitoring <br /> will vary depending upon regulatory requirements, which could significantly increase the total cost <br /> of the project <br /> Typical costs for monthly monitoring of an in-situ bioremediation system, in addition to standard <br /> I quarterly sampling, would be approximately S 1,500 00 per month Based on a two year treatment <br /> period, the total cost for in-situ bioremediation at the Chase Chevrolet - Van Buren site would be <br /> between $105,000 00 and $1315,000 00 <br /> 6"4 NATURAL ATTENUATION <br /> Natural attenuation, or passive bioremediation is a remedial alternative that relies on natural <br /> p � 1 <br /> processes to degrade hydrocarbons Biodegradation is the most important natural attenuation <br /> Imechanism No additional bacteria or nutrients are added to the soil Essential nutrients required for <br /> biodegradation are usually naturally present in the subsurface However, where high concentrations <br /> I of hydrocarbons are present, nutrients may be consumed before hydrocarbon remediation is <br /> complete Oxygen depletion in the subsurface is a characteristic of biodegradation The core of a <br /> contaminant plume is typically under anaerobic conditions and only the margins are aerobic <br /> Therefore, even though anaerobic biodegradation is much slower than aerobic biodegradation, <br /> anaerobic processes may dominate the degradation of contaminants Ground water movement will <br /> generally assist in the transport of nutrients in the saturated zone <br />