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Mining will ultimately result in the west pit fully excavated with dewatering <br />trenches surrounding the toe of pit excavation. In the simulation, the elevation of <br />the drain was set at 1.5 feet above the bottom of the pit wall. The dewatering <br />drain yields approximately 460 gpm. These values are consistent with <br />observations of seepage faces (2 to 4 feet above toe of wall) and seepage yields <br />for other similar gravel pits in the area. <br />2.4.6. West Pit Reclamation <br />The reclamation plan is to backfill the west pit excavation to approximate historic <br />grade with overburden materials from the excavation of the east pit. The <br />hydraulic conductivity of the overburden material is set at 10 ft/day. <br />2.4.7. East Pit Dewaterinq <br />The perimeter drains around the East Pit are set at 1.5 feet above the base of the <br />pit and yielded a total of about 1,040 gpm. <br />2.4.8. East Pit Reclamation <br />The east pit excavation will Tined with a compacted clay liner to disconnect it from <br />the natural ground water table and the river. The clay liner in the model has a <br />hydraulic conductivity of 0.003 ft/day as is required by the State Engineer. <br />Flying W Pit <br />Groundwater Modeling Report Revised June 28, 2005 <br />6of13 <br />