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' 15 June 1999 <br /> . AGE-NC Project No 98-0450 <br /> ' Page 24 of 27 <br /> 5 4 3 Feasibility <br /> No feasibility testing or studies concerning natural attenuation have been performed at the site Prior <br /> to initiation of natural attenuation, additional ground water characterization would be necessary as <br /> it is necessary to be able to demonstrate stability and extent of the ground water plume Fate and <br /> Transport modeling may be used to determine whether or not hydrocarbons in ground water pose <br /> a threat to area receptors <br /> Hydrocarbon concentrations are relatively Nigh at the site, and therefore,natural attenuation does not <br /> ' appear to be a cost- or time-effective method of remediation Installation of monitoring wells would <br /> be required to evaluate and monitor natural attenuation Natural attenuation of impacted ground <br /> water should not be considered an acceptable remedial alternative until hydrocarbon-impacted soil <br /> ' has been remediated and the extent of hydrocarbon-impacted ground water is known <br /> ' 5 4 4 Duration <br /> Natural attenuation is a slow process that can take as long as than 30 years or more for the <br /> hydrocarbon plume to reach levels comparable to those achieved by active remediation methods The <br /> duration required for natural attenuation is prohibitive as a viable remediation alternative for the site <br /> ' at this time <br /> ' 5 4 5 Estimated Costs <br /> To monitor and verify natural attenuation, a long-term monitoring program, possibly lasting more <br /> than 25 years, would be required Costs for natural attenuation can be significantly lower than the <br /> active remediation options However, additional characterization costs and periodic monitoring costs <br /> ' would accumulate over time and could potentially be significant depending on the duration and type <br /> of monitoring requiiements <br /> ' Generally, the initial cost to evaluate contaminant fate and transport as well as installation of <br /> monitoring wells would range from $10,000 to $30,000 Monitoring and reporting costs for natuial <br /> attenuation would range from $5,000 to $10,000 annually The total cost of natural attenuation for <br />' a duration of 10 to 25 years is estimated range from $60,000 to $280,000 L <br /> 6 0 RECOMMENDED CORRECTIVE ACTION ALTERNATIVES <br /> Several applicable remedial technologies have been considered for use at the site General categories <br /> Adianced GcoEn,,ironmcnlal,Inc <br />