ARCHIVED REPORTS_XR0005088 - Laserfiche WebLink

Home Browse Search

' I 1. February 2003 • AGE-NC Project No. 98-0520 tPage 12 of 21 ' 6.3.5. Duration Duration (and cost) is dependent on the volume of soil and water to be remediated, the number of t inoculation and Monitoring wells,the average concentrations of contaminants and nutrients,and the temperature and permeability of the soil. Theoretically, the radius of influence of the inoculation well should increase rapidly at first,then gradually decline as the affected volume increases and the bacteria encounter decreasing hydrocarbon concentrations toward the margins of the hydrocarbon plume. Shorter-chain hydrocarbons are typically consumed first and longer-chain hydrocarbons later. Remediation at sites with similar soil composition typically takes between 12 and 48 months. 6.3.6. Feasibility tNo feasibilitystudies for in-situ bioremediation have been performed at the site.-If bioremediation is chosen as the method of remediation, soil samples will be collected and analyzed for ' physicochemical properties necessary for'effective bioremediation. The results will be used to evaluate the need for nutritional enhancement, if necessary,.to facilitate effective biodegradation. lie. 6.3.7. Estimated Costs For In-situ Bioremediation ' The cost for in-situ bioremediation will vary,.depending upon the volume of inoculum required and the number of remediation wells to be inoculated; in addition, longer-chain hydrocarbons (diesel) will probably require a longer remediation period. Generally, the initiation cost for in-situ ' bioremediation will range from$35,000 to$75,000.Weekly and monthly monitoring generally costs between$10,000 to $20,000 annually; soil borings to monitor bioremediation progress typically averages $5,000 to $10,000 annually. Total costs for bioremediation of soil at the subject sits is estimated to be between $70,000 and$160,000. 6.4. MONITORED NATURAL ATTENUATION ' Natural attenuation, or passive bioremediation,'is a remedial alternative that relies on natural processes,to degrade hydrocarbons. Biodegradation is the most important natural attenuation mechanism.No additional bacteria or nutrients are added to the soil.Essential nutrients required for ' biodegradation. are commonly present 'naturally in the subsurface; however, where high concentrations of hydrocarbons are present, nutrients may be consumed before liydrocarbon remediation is complete. ' Oxygen depletion in the subsurface is another characteristic of passive biodegradation. The core of a contaminant plume typically exists under anaerobic conditions and only the margins are aerobic. 'Advanced GeoEnvironmental,Inc.