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Design calculations and detailed specifications for post -mining drainages <br />are presented in Exhibit 19, Drainage and Sediment Control Plan. All <br />post -mining drainages have been designed to pass the peak flows <br />resulting from a 100 -year, 24-hour storm event with a minimum freeboard <br />with 0.3 feet. <br />Post -mining drainages and temporary ditches will route any disturbed area <br />runoff to sedimentation ponds through the post -reclamation period to the <br />point of bond release. Following determination of reclamation success, <br />sedimentation ponds and temporary diversion ditches will be reclaimed <br />and post -mining drainages will be connected to existing natural drainages. <br />Where post -mining drainages intersect existing natural drainages, the <br />transition channel will be constructed to provide a smooth transition of <br />both channel configuration and flow. <br />4.05.18 STREAM BUFFER ZONES <br />There are no surface drainages within either the mine or loadout areas <br />which exhibit perennial flow characteristics or which support a significant <br />biological community. Large ephemeral streams, defined as having <br />drainage areas in excess of one (1) square mile, exist at the mine site and <br />loadout area. The Division has previously authorized EFCI mining <br />operations within buffer zones of large ephemeral streams. Relevant <br />operations include mine workings under Newlin Creek, and the loadout <br />surface disturbance adjacent to Oak Creek. <br />4.05-29 <br />Revised 6/23/15 <br />MR -68 <br />