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r-- T— . 16 August 2001 AGE-NG Project No 97-0312 Page 11 of 20 " c i 1 f t 7 2 6 Feasibility No feasibility studies for in-situ bioremediation have been performed at the site The longer-chain hydrocarbons that represent a majority of the contamination at the site would require a longer remediation.period Ifbloremediation is chosen as the method of remediation, soil samples should, ,be collected and analyzed for physicochemical properties necessary for effective bioremediation The ' results will be used to evaluate the need for parameter adjustment,if necessary,to facilitate effective biodegradation ' dia 727 Estimated Cost For In-Situ Bioremediation T - The cost for in-situ bioremediation will vary, depending upon the volume of inoculant required and the number of remediation wells to be inoculated Generally, the implementation cost for in-situ ' bioremediation will range from$45,000 to$75,000 Furthermore,weekly and/or monthly monitoring generally costs between $10,000 and $20,000 annually, soil borings to monitor bioremediation progress and sample analyses typically average$15,000 to$20,000 annually Therefore,the total cost ' could reach as much as $40,000 annually,based on a 36 to 48 month duration, the total cost for in- situ bioremediation,is estimated between$120,000 and$235,000 However, it should be noted that bioremediation durations in excess of 48 months are not uncommon 73 NATURAL xT E1,76AT O rH7'OSVn `IlV T EDLkT N 1 Passive remediation is a process that reties on natural processes to degrade petroleum hydrocarbons Natural attenuation, or passive' bioremediation, is a passive remediation method and requires a high level of characterization and long-term monitoring t 7 3 1 Principles Biodegradation is the most important natural attenuation mechanism No additional bacteria or ' nutrients are added to the soil Essential nutrients required for biodegradation are usually naturally present in the subsurface However,where high concentrations ofhydrocarbons are present,nutrients may be consumed before hydrocarbon remediation is complete Oxygen depletion in the subsurface ' is another characteristic of passive biodegradation The care of a contaminant plume typically exists under anaerobic conditions and only the margins are aerobic Therefore, even though anaerobic biodegradation is much slower than aerobic biodegradation, anaerobic processes may dominate the ' degradation of contaminants Natural attenuation is normally used where low concentrations of hydrocarbons are present or after completion of another method of remediation Advanced GeoEnvironmental,Inc 'r ' a �