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Central Facilities Area Collection Ditches. Culverts and Diversions- The collection ditches and culverts conveying runoff from thz disturbed areas at the czn[ral facilitizs area will adequately carry the flow resulting from the 10-yeaz, 24-hour event. The ditch collecting disturbed flow and diverting undisturbed flow at the coal processing waste disposal site will also be stable under the 10-year, 24-hour peak flow conditions. ~ Munger Creek Permanent Stream Channel Relocation- The combination channel, bank, and floodplain configuration of the relocated stream channel will safely pass the peak runoff of a 100-year, 24-hour precipitation event. The capacity of the reconstructed channel will be at least equal to the capacity of the unmodified channel immediately upstream and downstream of the reconstructed channel. C. Sedimentation Ponds Information dealing with sediment and runoff control is presented in Sections 2.2.7, 2.3.1, 2.3.4, 2.3.5, of Volume I, Appendix M of Volume V, and Sections 2.3.5, 2.3.6, 2.3.7, 2.3.8 and Appendix As of Volume VI of the permit application. This information has been reviewed by the Division for compliance with the rules and Regulations and the resulting analysis is presented below. Mine Bench Sediment Pond- The proposed pond at the mine bench is designed to hold a volume of runoff and sediment of 0.45 acre-feet. This capacity allows for the storage of runoff resulting from the 10-yeaz, 24-hour storm event (0.24 acre-feet), as well as storage of the sediment produced from the disturbance over atwo-year period (0.21 acre-feet). The Division requires that a sediment clean-out mazker be installed in the pond to indicate the level at which sufficient storage will remain for both runoff and sediment generated by the 10-yeaz, 24-hour storm event. The collector ditch into the pond will be stable under the flow from the ] 0-yeaz, 24-hour storm event. The emergency spillway is designed to convey flow from the 25-yeaz, 24-hour event without eroding. The design of the pond is presented in the amended application includes provisions for a dewatering device to dewater the pond down to the maximum sediment storage level. Refuse Pile Sediment Pond- The proposed sediment pond for the underground development waste disposal pile is designed for a total capacity of 0.185 acre-feet. This will allow for the detention of the volume of runoff from the ] 0-year, 24-hour event (0.12 acre-feet) in addition to a three-yeaz accumulation of sediment from the disposal pile (0.062 acre-feet). A sediment clean-out mazker must be installed which indicates the level at which sufficient storage remains in the pond for both runoff and sediment generated by the l0-yeaz, 24-hour storm event. 28