Laserfiche WebLink
Water Control Measures <br />Rule 4.09.1(13) requires that an appropriate underdrain be installed if seeps, springs <br />or waterways, natural or manmade, are in the coal waste disposal footprint area. A <br />June 2013 inspection of the site found that seepage from the Fire Mountain Canal <br />had surfaced in the upper diversion ditch. Wet areas were also noted below the <br />upper diversion ditch. The seepage did not cause any perceptible flow. The design <br />of a rock subdrainage system is detailed below. <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 Appendix B for detailed design information of the run -off and collection <br />ditches. <br />Sedimentation Pond <br />Sediment Pond J was 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 by Tammerin Kae Stover - Bishop, <br />Colorado Professional Engineer, No. 43402. See Map 22 -J. <br />The total drainage area associated with the new coal mine waste disposal area is <br />approximately 25 acres. The area was divided into separate watersheds draining <br />into run -off and collection ditches designed to handle the run -off from the 100 - <br />year, 24 -hour precipitation event. The drainage areas are shown on Map 20 in <br />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 2.4 acre feet of runoff. Sediment accumulation was estimated with <br />the use of the Universal Soil Loss Equation. The pond has been designed to <br />contain approximately 3.3 acre feet of water and 1.4 acre feet of sediment. The <br />sediment pond will be dewatered if it contains water above the maximum <br />sediment level. This dewatering event should occur within 48 hours after the <br />Volume XI <br />TR -91 - 5 - 12/14 <br />