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s 15 November 1995 AGE-NC Project No 95-0142 Page 15 of 19 ' method The extraction is performed using an automatic pump system to maintain capture characteristics in the aquifer and assure process requirements are maintained After treatment, the water is usually discharged into a storm drain or sanitary sewer A waste discharge permit is usually ' required for discharge ' 7 2 2 TREATMENT METHODS The documented presence of hydrocarbons will require treatment for the recovered water Two of I the most common methods of water treatment are air stripping and carbon adsorption Air stripping involves removal of volatile organic compounds from ground water by promoting the transfer of ' contaminants from the dissolved phase to the vapor phase Carbon adsorption utilizes granular activated carbon to simply"filter" organic compounds out of ground water ' A third, but less common method of above-ground treatment of water is bioremediation Similar to the pilot study performed at the site, contaminated ground water is "treated" by adding hydrocarbon- degrading microbes or by augmenting natural hydrocarbon degradation activities with introduction of nutrients 7 2 3 FEASIBILITY TESTING " _ No aquifer testing has been performed at the site A pump test could be performed on wells MW-1, ' MW-2 or MW-3 to determine aquifer properties, if necessary There are several disadvantages to "pump and treat methods" The more serious disadvantages ' include 1)extended cleanup periods,resulting in increased total costs, although the maintenance for this method is relatively cost-effective and 2) regulatory cleanup goals are rarely attainable, mostly due to persistent hydrocarbons detected in subsequent sampling events Ground water extraction is ' generally not a desirable method for remediation 7 2 4- DURATION Experience has shown that all systems involving ground water extraction require much more time ' than would be anticipated from aquifer tests and calculations of ground water discharge rates, and seldom achieve regulatory goals for ground water clean-up Systems typically operate for several years During this time, pumps and other equipment may need replacement several times The primary utility of pump-and-treat systems is in preventing migration of contaminated ground water I