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(4) Ponds, Impoundments and Diversions <br />The Sediment and Surface Water Control Plans are shown on Maps 13 and 14 for the East Portal <br />and West Portal respectively. The Operator submitted these plans as a technical revision to the <br />permit. These revisions have been necessary because of preparation plant construction, refuse <br />area construction, and the need for more efficient routing of disturbed water as well as ease of <br />maintenance of the overall drainage system. The area north of Ditches D11, and D19 to the <br />Highway 12 easement were graded, covered with subsoil and topsoil, mulched and seeded during <br />August and September of 1990. <br />The Operator has three sediment ponds which collect surface disturbance runoff from the East <br />Portal area. These ponds are 004, 007 and 008. A fourth pond, pond 005, was reclaimed in 2003, <br />as the area serviced by this pond was never used for mining related activities. These <br />sedimentation ponds and associated diversion ditches have been designed according to Section <br />4.05.6 of the DRMS Regulations. In addition, the diversion structures have been designed <br />utilizing the requirements of 4.05.3 and 4.05.4. Typical sections of the emergency spillways and <br />embankments of each sediment control structure are shown in Figure 3, Typical Embankment <br />Cross Section. Typical diversion sections are provided on Map 13 Sediment and Surface <br />Water Control Plan- East Portal. Table 20, Ditch Data, is a summary of the diversion (ditch) <br />data relating to Map 13. Table 21, Culvert Sizing and Table 22, Culvert Sizing Nomograph, <br />provide backup for culvert sizing as per requested drainage modifications. Table 23, Sediment <br />Pond Dimensions, is a summary of sediment pond dimensions. <br />The Operator will control West Portal drainage using ditches, containment areas and bypass <br />culverts. All structures are shown on Map 14, Sediment and Surface Water Control Plan -West <br />Portal. Calculations are found in Exhibit 19, Sediment Design Specifications. <br />Runoff from the west DWDA is routed through a series of diversion ditches and will be routed to <br />Containment Area No.2. The sedimentation control plan for the west DWDA is contained in <br />Exhibit 19(22) and was evaluated based on the 100 -year, 24 -hour event. Runoff from the <br />undisturbed upland areas to the west are diverted around the pile in ditch D49. Runoff from a <br />small undisturbed upland area east of the pile is routed through the diversion ditches and routed to <br />containment area 2. <br />Ditches 27 and 69 will direct runoff to Containment Area 2. Containment Area 2 has been <br />designed to contain the 25 -year, 24 -hour event, per Rule 4.05.9(2)(e) and as such an emergency <br />spillway system is not required. The total drainage area for Containment Area 2 is 13.14 acres. <br />A total of 1.93 acre -feet of storage is required to handle the 25 -year 24 -hour event. The required <br />water storage volume is 1.84 acre -feet, and the three -year sediment volume is 0.1 acre -feet. <br />Ditch 28 will direct a combination of disturbed, and undisturbed runoff to Containment Area 1. <br />A total of 1.51 acre -feet of storage is required to handle a 10 -year 24 -hour event and 2.01 acre - <br />feet for a 25 -year 24 -hour event. The three -year sediment storage volume is 0.07 acre -feet. <br />Containment Area 1 also controls drainage from the sediment drying area and the soil storage <br />area associated with the West DWDA. <br />The sediment drying area will be located where the non -coal waste area was previously <br />permitted. Material excavated from ditches, catchments and sediment ponds will be placed in the <br />sediment drying area and allowed to dry before being hauled to a suitable stockpile. Material <br />from the sediment drying area may be used as plant growth medium. <br />TR -65 Page 2.05 -9 Revised 06/15/12 <br />