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<br /> <br />Technical Revision No. 73 <br />October 13, 1994 <br />Page 2 <br />or degrade to soil material and will be free of coal, clay and <br />other non-durable material. <br />5. The main stem of the proposed underdrain is shown as <br />underlying the entire axial length of the pile. The <br />underdrain should not be open to surface inflow or direct <br />infiltration from up gradient. The Division recommends that <br />a five foot setback from the up gradient toe of the pile and <br />a filter fabric termination flap to assist in preventing an <br />contamination of the underdrain matrix by sediment. <br />RECLAMATION <br />1. MCC has stated in the application that the pile will be <br />covered with four feet of cover. As MCC is only stripping one <br />foot of topsoil from this area, what will be the source for <br />the additional three feet of material required? <br />2. What is the life of this pile? Will it be permanently <br />reclaimed once the 17,000 cubic yards generated from the <br />development of the Lone Pine Gulch fan intake and return <br />entries is placed in the disposal area? <br />SURFACE WATER CONTROL PLAN <br />1. The Division disagrees with the selection of 81 for a curve <br />number; however, a worst case has been modelled with a curve <br />number of 91 and the limit for settleable solids has still <br />been met. <br />2. The 100-year ditch design was only sized for a discharge of <br />0.26 cfs. SEDCAD shows the peak discharge for the undisturbed <br />area to be 0.53 cfs. The size of the ditch should be <br />modified. <br />3. It appears that some of the runoff from the pile will flow <br />into the diversion ditch. If this is correct, then the ditch <br />design should be revised to account for the additional runoff <br />and demonstrate that the flow would meet effluent.limitations. <br />4. Rule 4.09.2(7) requires that surface runoff from the fill <br />surface shall be diverted to stabilized channels off the fill <br />which will safely pass the runoff from a 100-year 24-hour <br />precipitation event. MCC's surface water control plan <br />includes only an upper diversion ditch and two silt fences <br />placed at the toe and midslope of the fill. The disturbed <br />