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21 <br />such an emergency spillway system is not required. The total drainage area for <br />Containment Area 2 is 13.14 acres. A total of 1.93 acre -feet of storage is required to <br />handle the 25 -year 24 -hour event. The required water storage volume is 1.84 acre - <br />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 <br />Containment Area 1. A total of 1.51 acre -feet of storage is required to handle a 10- <br />year 24 -hour event and 2.01 acre- feet for a 25 -year 24 -hour event. The three -year <br />sediment storage volume is 0.07 acre -feet. Containment Area 1 also controls drainage <br />from the sediment drying area and the soil storage area associated with the DWDA <br />#3. <br />The sediment drying area will be located where the non -coal waste area was <br />previously permitted. Material excavated from ditches, catchments and sediment <br />ponds will be placed in the sediment drying area and allowed to dry before being <br />hauled to a suitable stockpile. Material from the sediment drying area may be used <br />as plant growth medium. <br />Ditch 29 collects runoff from 67.2 acres of undisturbed runoff and directs this runoff <br />to the lay down area without impacting any disturbed area. Culvert C -27 has been <br />installed at the east end of the lay down area to handle peak flows from Drainage <br />Basins CC and DD as shown on Map 13A- Drainage Basins. <br />Ditches 39a and 39aa are proposed to route storm water around the cut slope of the <br />substation and rock dust system to maintain the integrity of the slope. At the time of <br />construction, the slope material characteristics will be evaluated to determine if a <br />drop structure is necessary to carry the cut slope runoff. The details of the cut slope <br />are included as Figure 2d. <br />Sedimentation control for the RDA haul road is shown on Map -13. Runoff from the <br />haul road will be managed with ditches and culverts and the design for each structure <br />is included in Exhibit 19(24). Runoff from the haul road is not considered to be in <br />the disturbed area as deemed by Rule 4.05.2(4) and is therefore not routed to a <br />Sediment Pond. <br />Sedimentation control at the Bates Portal is shown on Map 13 -A Sediment and <br />Surface Water Control Silo Area. Six new ditches and four new culverts and the <br />design size and routing of each structure are provided in Exhibit 19 (16). Runoff <br />from the 10 -year, 24 -hour event at the Portal will be routed to Pond 007. <br />The C & W train shop, 10 -stall garage and other associated structures are located on <br />the west side of the east mine sedimentation control system. The land slopes <br />approximate 2% from the C & W train shop to the east towards pond 7. Flow from <br />this general area will be collected in either ditch D -5 or D -6 and conveyed to <br />sediment pond 7 and can be found on Map -13C, West Side of the East Mine - <br />Sedimentation Control Plan. <br />Section 2.05 TR -70 03/02/2015 <br />