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J r 04 March 1996 AGE-NC Protect No 95-0144 - Page 15 of 18 ' 7 2 GROUND WATER EXTRACTION 7 2 1 BASIC PRINCIPLES There are several different methods for treatment of extracted ground water;which are collectively ' called "pump and,treat" As the name indicates, all methods involve extraction and transfer of y contaminated ground water from the aquifer to an above-ground treatment or disposal/recycling facility 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 Two of the most common methods of water treatment are air stripping and carbon adsorption Air stripping involves removal of volatile organic compounds ft om ground water by promoting the transfer of contaminants from the dissolved phase to the �apor 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 For this method, contaminated ground water is "treated" by adding hydrocarbon-degrading microbes or by augmenting natural hydrocarbon degradation activities by the introduction of nutrients ' 7'2 3 FEASIBILITY TESTING Thee e are several disadvantages to "pump and treat methods" Z he most pronounced disadvantages ' include 1) extended cleanup periods, resulting in elevated total costs although the maintenance of this method is relatively cost-effective and 2) regulatory cleanup goals are rarely attainable, mostly due to recurring hydrocarbons in subsequent sampling events Ground water extraction is generally ' not a desirable method for remediation No aquifer testing has been performed at the site However, sands are present from approximately 5 feet above to 13 feet below ground water surface 7 2 4 DURATION ' Experience has shown that all systems involving ground water extraction require much more tine 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 P