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' 18 February 1997 <br /> • AGE-NC Project No 95-0104 <br /> Page 16 of 22 <br /> I If air sparging is chosen for ground water remediation, vapor extraction will be used for vadose zone <br /> sod remediation Therefore, extraction equipment and monitoring costs would be included under soil <br /> vapor extraction estimates <br /> 7 2 GROUND WATER EXTRACTION <br /> I7 2 1 BASIC PRINCIPLES <br /> There are several different methods for treatment of extracted ground water, which are collectively <br /> called "pump and treat" As the name indicates, all methods involve extraction and transfer of <br /> contaminated ground water from the aquifer to an above-ground treatment or disposal/recycling <br /> facility The extraction is performed using an automatic pump system to maintain capture <br /> characteristics in the aquifer and to assure that process volume requirements are maintained After <br /> I treatment, the water is usually discharged into a storm drain or sanitary sewer A waste discharge <br /> permit is usually required for discharge <br /> r • 7 2 2 TREATMENT METHODS <br /> I The documented concentrations of hydrocarbons will require treatment for the extracted water Two <br /> of the most common methods of water treatment are air stripping and carbon adsorption Air <br /> stripping involves removal of volatile organic compounds from ground water by promoting the <br /> Itransfer of contaminants from the dissolved phase to the vapor phase Carbon adsorption utilizes <br /> granular activated carbon to simply "filter" organic compounds out of ground water <br /> A third, but less common method of above-ground treatment of water 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 2 3 FEASIBILITY TESTING <br /> Aquifer testing has not been performed at the site Site-specific testing would have to be performed <br /> Iprior to initiation of a pump and treat method <br /> There are several disadvantages to "pump and treat" methods The most serious disadvantages <br /> Iinclude 1) extended cleanup periods, resulting in increased total costs, although the maintenance for <br /> • this method is relatively cost-effective and 2) regulatory cleanup goals are rarely attainable, mostly <br /> due to persistent hydrocarbons detected during subsequent sampling events Ground water extraction <br /> is generally not a desirable method for remediation However, this technology is useful for hydraulic <br />