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I . Water Control Measures <br />Rule 4.09.1(13) requires that an appropriate underdrain be installed if seeps, <br />springs or waterways, natural or manmade, are in the coal waste disposal footprint <br />area. At the time of this writing, no seeps, springs, or waterways, natural or <br />manmade are identified in the coal waste disposal footprint area. The site is to be <br />inspected for springs or seeps as work progresses, and an underdrain installed only <br />for cause. This would be an alternate design as permitted under Rule 4.09.1(3) and <br />4.10.3(5). <br />The run-off and collection ditches are shown on Map 15. Run-off from the <br />benches will be directed to the east and west to collection ditches. The east and <br />west collection ditches D-J8 and D-J9 are; 1) lined with riprap where necessary <br />to ensure they are stable; 2) constructed off the fill and; 3) designed to safely <br />pass the run-off from the 100-year, 24-hour precipitation event. <br />See Volume III, Exhibit 8 for detailed design information of the run-off and <br />collection ditches. <br />i ~ Sedimentation Pond <br />Sediment Pond J will be modified so it will contain the additional run-off from the <br />coal mine refuse disposal area. The sediment pond and the general drainage <br />plan for the waste disposal site were prepared under the direction of J. E. Stover, <br />Colorado Professional Engineer, No. 19230. See Map 22-J. <br />The total drainage area associated with the new coal mine waste disposal area <br />is approximately 25 acres. The area was divided into separate watersheds <br />draining into run-off and collection ditches designed to handle the run-off from <br />the 100-year, 24-hour precipitation event. The drainage areas are shown on <br />Map 20 in Volume II. <br />The modified sediment pond was sized to contain the run-off from the 10-year <br />24-hour precipitation event (1.8 inches). This storm event will generate <br />approximately 2.6 acre feet of runoff. Sediment accumulation was estimated <br />with the use of the Universal Soil Loss Equation. The pond has been designed <br />to contain approximately 2.6 acre feet of water and 0.2 acre feet of sediment. <br />The sediment pond will be dewatered if it contains water above the maximum <br />TR-45 - 5 - 12/06 <br />APp2a;~r~ <br />7/3~0-~ <br />