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• Surface runoff from active refuse placement areas will be controlled by <br />localized drainage and control measures in these areas as well as by the <br />permanent collection ditches which encompass the coal refuse pile area. The <br />coal refuse pile ditches on the north, west and south side of the refuse pile <br />area have been designed to pass the peak runoff resulting from a 100 -year, <br />24 -hour storm event with a minimum freeboard of 0.3 feet. The locations of <br />these ditches are shown on the Mine Surface Facilities Map, (Map 18) and <br />detailed design calculations are presented in Exhibit 19, Drainage and <br />Sediment Control Plan. These ditches collect and route all surface runoff <br />from the refuse pile area to sedimentation Pond No. 4 for settlement of <br />suspended solids and treatment if necessary. Operation of this sedimentation <br />pond under EFCI's NPDES permit complies with applicable water quality <br />regulations and effectively mitigates any potential surface water quality <br />impacts. <br />As discussed in the following groundwater quality discussion, potential <br />impacts of groundwater leachate form the coal refuse pile on the surface <br />water system are expected to be negligible since the volume of leachate will <br />• be effectively minimized by the arid climate of this area, compaction and <br />grading of coal refuse materials, diversion of up- gradient drainage from <br />undisturbed areas, and reclamation of the completed coal refuse pile. <br />EFCI's ongoing mining operations result in groundwater inflows to the mine <br />workings. These inflows originate both from areal movement of groundwater <br />within the interval being mined as well as limited vertical infiltration <br />where subsidence fractures intersect abandoned and flooded underground mine <br />workings. In order to minimize the effects of groundwater on ongoing mining <br />operations, EFCI has developed a mine dewatering program utilizing a series <br />of underground sumps, pumps, and water pipelines as described in Section <br />2.05.3, Operation Plan. <br />RF.cF_►vF_c <br />OCT 25 1994 <br />• Division of Wne\a15 & Geology <br />C:\TM\860W0L.2\REC.PLN <br />10/24/94 9:08em WP51 /cmc 2.05.6 -19 Revised - 9/30/94 <br />