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27 June 1996 <br /> AGE-NC Project No. 95-0118 <br /> Page 19 of 23 <br /> Contaminated ground water is "treated" by adding hydrocarbon-degrading microbes or by <br /> '= augmenting natural hydrocarbon degradation activities with introduction of nutrients. <br /> Fr, <br /> 8.2.3. FEASIBILITY TESTING <br /> -_1 Aquifer testing has not been performed at the site. A pump test could be performed on wells MW-2 <br /> or MW-3 to determine aquifer properties, if necessary. <br /> There are several disadvantages to "pump and treat methods The more serious disadvantages <br /> include: 1) extended cleanup periods, resulting in increased total costs, although the maintenance <br /> for this method is relatively cost-effective and 2) regulatory cleanup goals are rarely attainable, <br /> mostly due to persistent hydrocarbons detected in subsequent sampling events. Ground water . <br /> extraction is generally not a desirable method for remediation. <br /> 8.2.4. DURATION <br /> Experience has shown that all systems involving ground water extraction require much more time <br /> than would be anticipated from aquifer tests and calculations of ground water discharge rates, and <br /> seldom achieve regulatory goals for ground water clean-up. Systems typically operate for several <br /> years. During this time,pumps and other equipment may need replacement several times. Currently, <br /> the primary utility of pump-and-treat systems is to control migration of contaminated ground water. <br /> 8.2.5. COST <br /> .`' Ground water extraction is usually a very costly method of ground water treatment. Cost for <br /> installation of a"pump and treat" system typically ranges from $20,000 to $30,000, including the <br /> installation of one large-diameter extraction well.However, once extracted,the contaminated water <br /> must be treated or disposed. Treatment is highly dependant upon the concentrations of dissolved <br /> hydrocarbons in the ground water. For the Elkhorn site, the cost per gallon could be as great as <br /> $2.00,based upon the extraction/treatment of approximately 175;000 to 200,000 {45 feet X 5 feet <br /> in depth X 7.48 gal./cubic foot)gallons of contaminated ground water. Costs for the entire treatment <br /> project would likely be between. $200,000 and $450,000. . <br /> 8:3. IN SITUBIOREMEDIATION/BIOENHANCEMENT <br /> 8.3.1. BASIC PRINCIPLES <br /> Bioremediation involves the introduction of hydrocarbon-degrading microbes or supplemental <br />