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Ditch 29 collects runoff from 67.2 acres of undisturbed runoff and directs this runoff to the lay down area without <br />impacting any disturbed area. Culvert C -27 has been installed at the east end of the lay down area to handle peak flows <br />from Drainage Basins CC and DD as shown on Map 13A— Drainage Basins. <br />Ditches 39a and 39aa are proposed to route stormwater around the cut slope of the substation and rock dust system to <br />maintain the integrity of the slope. At the time of construction, the slope material characteristics will be evaluated to <br />determine if a drop structure is necessary to carry the cut slope runoff. The details of the cut slope are included as Figure <br />2d. <br />Sedimentation control for the RDA haul road is shown on Map -13. Runoff from the haul road will be managed with <br />ditches and culverts and the design for each structure is included in Exhibit 19(24). Runoff from the haul road is not <br />considered to be in the disturbed area as defined by Rule 4.05.2(4) and is therefore not routed to a Sediment Pond. <br />Sedimentation control at the Bates Portal is shown on Map 13 -A Sediment and Surface Water Control Silo Area. Six new <br />ditches and four new culverts and the design size and routing of each structure is 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 the west side of the east mine <br />sedimentation control system. The land slopes approximate 2% from the C & W train shop to the east towards pond 7. <br />Flow from this general area will be collected in either ditch D -5 or D -6 and conveyed to sediment pond 7 and can be found <br />on Map -13C, West Side of the East Mine - Sedimentation Control Plan. <br />A small area exemption has been established for subsoil storage pile #1 due to its proposed location outside of areas <br />where disturbed runoff will be routed to a sediment pond. Alternative sedimentation control for this area is provided by <br />berms and silt fences. The design of the silt fences are included Exhibit 19(16). This SAE area is shown on Maps 11 and <br />12. <br />The proposed DWDA stormwater management above, around and on the waste pile was evaluated for a 100 year, 24 -hour <br />storm event. The results indicate that the management system already in place for the site will safely pass the storm with <br />the recommendation that the berms and ditches are field verified to be constructed as designed. The stormwater routing <br />near the DWDA is shown on Figure 2e. The runoff above (North) is diverted through Ditch D -11 through culvert C -30, <br />ditch D -1, culvert C -26, and ditch D -32 to the river. This is shown in Figure 2e. Exhibit 39 Sediment Design <br />Specification – Development Waste Disposal Area demonstrates that the existing ditches are appropriately sized to carry <br />the stormwater above the DWDA. <br />The DWDA runoff is routed through a small catchment into culvert C -13 and to pond 007. The engineering evaluation of <br />the DWDA is included as Exhibit 39 Sediment Design Specification – Development Waste Disposal Area. As part of <br />TR -60 the DWDA was expanded to the west in order to gain more storage area for development waste. The drainage area <br />evaluated for TR -60 is 5.1 acres and includes the DWDA, and a small portion of the haul north of the pile that will flow <br />into Ditch D -12. The 100 year, 24 -hour storm precipitation is 4.2 inches. SedCad calculates the peak flow to be 15.58 cfs <br />with 1.47 acre -feet of total runoff. The required ditch size to convey that flow is a trapezoidal channel of bottom width 3.0 <br />ft, height of 1.5 ft, side slopes of 1:1 and a minimum slope of 1 %. Existing ditches are of this recommended size and <br />shape. The minimum pipe diameter needed to convey the 100 year, 24 -hour peak flow to pond 007 is 24 inches. The <br />existing culvert is 24 inches. The pipe installation should have a minimum of 1.2 feet of material from the top of the pipe <br />to the top of the bank (i.e. the lowest point on any top of berm/top of bank around the DWDA shall be no less than 1.2 feet <br />above the top of the 24 inch outlet pipe. <br />A small area exemption has been established for a material storage area and associated activities located south of sediment <br />pond 7 due to its location outside of an area where runoff will be routed to a sediment pond. Alternative sedimentation <br />control for this area is provided by berms and a silt fence. The design of the silt fence is included Exhibit 19(17). This <br />SAE area is shown on Map 11 Sheets 1, 2 and 3. <br />The cut slopes above the upper diversion ditch at the Bates Portal fall under Rule 4.05.2(4) which states in part; for the <br />purposes of 4.05.2, "disturbed area" shall not include those areas in which only diversion ditches sedimentation ponds, <br />other treatment facilities, or roads are installed in accordance with the performance standard requirements of this Rule. <br />The cut slopes will be covered with a straw blanket and seeded since there is concern the slopes may contribute suspended <br />solids to stream flow or runoff outside the permit area. The straw blanket will be maintained until vegetation is <br />established. <br />TR -66 Page 2.05 -10 07/25/12 <br />