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DEC 07 '8EL 15: 3S1 LEV IHE-FF E, H. E. F .4 <br />LEVINEFRICKE <br />Results of slug testing in monitoring wells indicate a range of <br />hydraulic conductivity values for subsurface sediments between <br />0.2 feet/day in peat at well N-7 to 40 feet/day in poorly-graded <br />(well-sorted) sand at well N-I6. The well and boring log; in the <br />vicinity of Cook Road suggest that the shallow aquifer consists <br />primarily of sand with some silt and that the peat area is fairly <br />limited (see Mark Group October 6, 1987 report for cross-sections <br />of sediments). Therefore, the upper end value of 40 feet/day was <br />used to evaluate extraction alternatives using an analytic model <br />of ground-water flow. This higher value will also give a <br />conservative estimate of the capture area for a given extraction <br />rate (i.e., smaller area of capture for a given extraction rate). <br />COMPUTER MODELING OF EXTRACTION SYSTEMS <br />Use of a homogeneous aquifer model (THEIS developed by S. S. <br />Papadopulos and Associates, 1980) for the Theis equation suggests <br />that two wells along Cook Road pumping at 2.5 gpm each will <br />capture ground water in the area containing free product. Figure <br />3 depicts the calculated capture area and well location for this <br />proposed extraction scenario with a total flow of 5 gpm of ground <br />water. <br />Also shown on Figure 3 is an additional product extraction well <br />near existing well N-7. The low hydraulic conductivity value of <br />the peat material tested in well N-7 suggests that it would take <br />a considerable length of time for petroleum to migrate from this <br />area to Cook Road and be withdrawn. To expedite removal of <br />petroleum product, a product extraction well is proposed near N-7 <br />to remove product only and thereby reduce the overall time for <br />remediation. The extraction rate for this well is estimated to <br />be less than 0.5 gpm of petroleum. Because of the relatively <br />limited hydraulic effect that this well is calculated to have on <br />ground water capture, it was not explicitly modeled. <br />EXTRACTION SYSTEM DESIGN SUMMARY <br />Results of the field investigation, data review and computer <br />modeling were used to develop a conceptual extraction system <br />design for the Site. <br />Components of the design include placement of three extraction <br />wells, estimation of product and ground-water extraction; storage <br />and disposal of extracted product; and treatment and disposal of <br />extracted ground water.