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' 11 February 20.03 <br /> " <br /> AGE-NC Project No. 98-0520 <br /> Page 14'of 21 <br /> well with volatile organic compounds,but less successfully with longer-chained hydrocarbons,such <br /> ' as commonly occur in diesel fuel. Carbon adsorption utilizes granular activated carbon to simply <br /> f "filter" organic compounds out of ground water. <br /> A third, but less common method of above-ground treatment of wateris is bioremediation. <br /> Contaminated ground water is "treated" by adding hydrocarbon-degrading microbes or by <br /> augmenting natural hydrocarbon degradation activities with the introduction of nutrients. <br /> ' 7.1.2. Feasibility Testing <br /> Aquifer testing has not been performed at the site; Site-specific testing would have to be performed <br /> prior to initiation of a pump and treat method. At the present time, ground water elevation is at <br /> approximately 24 feet bsg, within the less permeable, 15-foot thick clayey silt Iayer that is <br /> sandwiched between overlying and underlying sands. r <br /> There are several disadvantages to "pump and treat"methods, which include: 1) extended cleanup <br /> periods, resulting in increased total costs, although the maintenance for this method is relatively <br /> ' • cost-effective and 2) regulatory cleanup goals are difficult to attain, mostly due to persistent <br /> hydrocarbons detected during subsequent sampling events. <br /> ' This technology is useful for hydraulic control to prevent-spreading of the contaminant plume. <br /> Minimizingwater disposal costs will significantly increase feasibility of this method. <br /> 7.1.3. Duration <br /> ' Experience has shown that all systems involving ground d water extraction require much more time <br /> than would be anticipated from aquifer tests and calculations of ground water discharge rates, and <br /> ' the method seldom achieves regulatory goals for ground water clean-up. Systems typically operate <br /> for several years.During this time,pumps and other equipment may need replacement several times. <br /> 7.1.4. Cost <br /> ' Ground water extraction is usually a very costly method of ground water treatment. Costs for <br /> installation of a "pump and treat" system typically ranges from $30,000 to $50,000, including the <br /> installation of large-diameter extraction wells. Once extracted, the contaminated water must be <br /> 1 treated or disposed. Treatment is highly dependant upon the concentrations -of dissolved <br /> hydrocarbons in the ground water; the cost per gallon couldbe as great as $2 based on the <br /> Advanced GeoEnvironmental,Inc. <br />