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' 29'Apri12005. ; AGE-NC Project No. 98-0440 Page 13 of'18 costs could accumulate overtime and potentially be considerable depending on the duration and type'- monitoring ype'monitoring requirements: ' ;Fate.and Transport Modeling may be used to-demonstrate that,hydrocarbons'in soil:do,not'p"se;a .threat to groundwater. Where grourid water has been impacted modeling may be used to,evaluate the"possibility of hydrocarbons to impact,nearby ground water receptors. 7.0. GROUND WATER REMEDIATION ALTERNATIVES ' 'AGE considers ground water extraction; In-situ bioremediation/bioenhancement,.and monitored , natural attenuation as' appropriate remedial.technologies. or strategies to consider to .address ' hydrocarbon-impacted.ground water on the-site. ' .7.1. , GROUND WATER'EXTRAC-TTON ; 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 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 to assure that process volume requirements are maintained. After treatment;,the water is usually discharged into a'sanitary sewer or separate storm sewers. 7.L 1. Ground Water.Treaiment'Methods. The documentedpresence of dissolved hydrocarbons will require treatment for the recovered water. Two of the'most common methods of water treatment,afe air stripping and;carbon adsorption. Air stripping involves:removalof volatile organic compounds,from ground water by promoting'the transfer of contaminants from the dissolved phase to the vapor phase.Theprocess usually works well , with volatile organic compounds, but less successfully'with longer-chained.hydrocarbons, such-as ; commonly occur in diesel'fuel..Carbon adsorption,utilizes granular activated carbon to simply �!5 "filter" organic compounds out of ground"water: Af:third, but'•less common method of above-ground treatment of .water is bioremediation. Contaminated ground water is,. "treated",'. by 'adding hydrocarbon-degrading microbes or, by augmenting natural hydrocarbon' degradation• activities with the introduction •of nutrients. Additionally,the-removal of ground water through,"batch"treatment for off-site disposal could be Alimited,remediation alternative; { s, Advanced GeoEnvironmentel,Inc.