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' 15 June 1999 <br /> . AGE-NC Project No 98-0450 <br />' Page 23 of 27 <br /> of 24 to 36 is estimated <br />' 5 3 6 Estimated Cost <br /> Prior to conducting bioremediation, a feasibility study would be require at the site In-situ <br /> bioremediation would require the installation of several ground water monitoring wells for <br /> inoculation and monitoring of remedial effectiveness Feasibility analysis, well installation, and <br /> microorganisms and nutrients is estimated to cost between $25,000 and $65,000 Monitoring costs <br /> 1 would vary depending upon regulatory requirements,which could sigmficantly increase the total cost <br /> of the alternative Typical costs for monthly monitoring of an in-situ bioremediation system, in <br /> addition to standard quarterly sampling, would be approximately $1,500 00 per month Based on a <br />' 24 to 36 month treatment period, the total cost for in-situ bioremediation at the site would be <br /> between $60,000 and $120,000 <br /> 5 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 extensive site and contaminant plume characterization and Iong-term monitoring <br />' 5 4 1 Principles <br /> As with natural attenuation in soil (Section 4 4), biodegradation is the most important natural <br />' attenuation mechanism for impacted ground water No additional bacteria or nutrients are added to <br /> the ground water Essential nutrients required for biodegradation ate commonly naturally present <br /> in the saturated zone However, where high concentrations of hydrocarbons are present, nutrients <br /> may be consumed before hydrocarbon remediation is complete Oxygen depletion in ground water <br /> is another characteristic of passive biodegradation Natural attenuation is normally selected where <br />' low concentrations of hydrocarbons are present or after completion of another method of <br /> remediation <br />' 5 4 2 Monitoring Activities- <br /> Installation of a ground water monitoring well network would be required to monitor fol potential <br /> contaminant migration and to confirm the progress of natural attenuation Typically, ground water <br /> monitoring wells would be monitored on an annual basis for the duration of the project <br /> Advanced GeoEm ironniental,inc <br /> r <br />