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0Ict 10 1996 ? 18PM IEG IE ,HNOLGGEES No 39-11 P 4F9.4 <br />' tresh air activated carbon <br /> rmtllatar t iter <br /> used air �: <br /> _ cleaned air <br /> soil air removed <br /> /via suction <br /> stnipping zone <br /> working water level <br /> --5 �- <br /> :., r: �ou Irttrodudion <br /> r *- <br />' resting water level <br /> •1 <br /> extensive groundwater <br /> fClrCulatlah <br /> • �� !!! borehole filbriq <br /> filte�et seoiing�I <br /> quiter bottom <br />' Figure 2. UVB method, driven by the air bubble effect. <br /> been considered: j' <br /> When there is no (or negligible) natural groundwater flow, the sphere of influence <br />' (or the range, R) of a UVB is of interest. <br /> • When natural groundwater flow is significant, the extent of the capture zone has to <br /> be determined for locating the well installations at a remediation site, <br />' The resulting flow field of one or several UVB installations differs from the <br /> natural groundwater flow field only in a limited area around the UVB. This is because <br /> sinks and sources are located at the bottom and top of the same aquifer, each at places <br />' with the same horizontal coordinates. The effected area can, therefore, be limited to the <br /> sum of the areas of mfluence of all the UVBs.When only confined aquifer conditions are <br /> considered to reduce the computational effort, the flow field of each UVB can be <br /> superimposed onto those of other UVBs and of the natural groundwater flow field. <br /> To estimate the sphere of influence and the capture zone of a UVB, numerical <br /> investigations have been performed. To calculate the complex three-dimensional flow <br /> field of a single UVB or a UVB field with minimal effort, the following simplifications <br /> and assumptions have been used: <br /> • The aquifer thickness is constant. <br /> Only confined aquifer conditions are considered in the calculation, even if the <br /> natural aquifer is phreatic. <br />' • The aquifer structure is assumed radially homogeneous to hydraulic conductivities. <br /> Horizontal layers, each with different conductivities, can be used. The hydraulic <br />