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�W��� <br /> June 21, 1993 Working To Restore Nature <br /> ARCO Service Station No 2130 <br /> I <br /> vadose zone is accomplished using a conventional vapor-extraction system The capture <br /> zone of an air sparging well and the number of air sparging wells necessary to provide site <br /> coverage are highly influenced by the permeability and lithology of sediments below and <br /> above the water surface Soil lithology within the saturated and vadose zones must allow <br /> air transmission for the air sparging/vapor collection to be successful In addition, it is <br /> desirable to introduce air into the saturated zone at depths that will create a sufficiently <br /> large sparge radius of influence and reduce the number of sparge points required to provide <br /> the necessary coverage Field pilot testing is used to evaluate a site specific capture zone <br /> for air sparging wells, number of sparging wells required to provide site coverage, <br /> installation depth of sparge points, optimal sparge air flow rate, hydrocarbon removal rate, <br /> 1 <br /> and system design criteria. <br /> Indicators of sparge effectiveness are those parameters that either directly or indirectly <br /> demonstrate the mass removal of hydrocarbons from ground water and/or the capillary <br /> fringe Technical literature on air sparging indicates a variety of methods for data <br /> evaluation have been used to estimate sparging effectiveness and a sparge radius of <br /> influence. For this study, the selected indicators of mass removal from ground water and <br /> 0 the capillary fringe are reductions in dissolved TPHg in ground water and increases in TPHg <br /> vapor concentration immediately above the ground water surface Indicators of sparge <br /> influence (or the zone that the vertical and lateral migration of air bubbles occurs) are <br /> 10 increases in dissolved oxygen, decreases in dissolved TPHg and ground-water elevation <br /> changes and to a lesser degree pore pressure increases <br /> When sparging only, injected air creates a soil pore pressure gradient above the ground <br /> water surface leading away from the sparge point which (according to literature) extends <br /> beyond the area of bubble migration within the saturated zone While the use of vadose <br /> zone pressure gradients have been used in part to evaluate sparge radius of influences, <br /> i <br /> 30003-8 2 <br />