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1 <br />' 20 January 2005 <br /> AGE-NC Project No 97-0343 <br />' Page 18 of 21 <br />' 10 2 3 Duration <br /> Based on an extraction rate of approximately 3 to 5 gallons per minute, the majority of extractable <br />' hydrocarbon-Impacted ground would be extracted within a b- to 18-month period <br />' 10 2 4 Cost <br /> Ground water extraction treatment costs are highly dependant upon the type of dissolved <br />' hydrocarbons in the ground water and the site geological characteristics Costs for Installation of a <br /> ground water well extraction system typically range from$8,000 to$10,000,based upon the number <br /> and total depth of wells Once ground water Is extracted, the contaminated water will require <br />' disposal(I a on-site discharge Into municipal sewer/storm drain system or transportation to off-site <br /> waste water treatment facility) If discharging Into a municipal sewer/storm drain system Is selected, <br /> then an on-site treatment (I e activated carbon and/or air stripping) will be necessary prior to <br /> Idischarging <br /> Based on the concentrations of TPH-g and TPH-d encountered at the site, the cost for on-site <br /> treatment utilizing activated carbon and/or air stripping technologies may be between $0 03 and <br /> $0 05 per gallon when discharging Into a municipal storm drain/sewer systems Installation and <br /> operation of an on-site activated carbon and/or air stripping ground water treatment system, <br /> Including the quarterly monitoring and sampling,report preparation and permit fees An estimate of <br /> the costs for utilizing onsite treatment should range between$100,000 and$235,000, depending on <br /> duration and gallons of water removed <br /> I10 3 NATURAL ATTENUATION <br /> Natural attenuation, or passive bioremediation, is a remedial alternative that relies on natural <br /> processes to degrade hydrocarbons Natural attenuation is a passive remediation method and does <br /> require a high degree of site characterization and long-tern monitoring <br /> 10 3 1 Principles <br /> As with natural attenuation in soil, biodegradation is the most Important natural attenuation <br /> mechanism for Impacted ground water No additional bacteria or nutrients are added to the ground <br /> water Essential nutrients required for biodegradation are usually naturally present in the saturated <br /> zone However,where high concentrations of hydrocarbons are present,nutrients may be consumed <br /> before hydrocarbon remediation Is complete Oxygen depletion In ground water is another <br /> Advanced GeoEnvironmental,Inc <br />