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4.8.1.4 Sediment Ponds <br />All runoff from disturbed areas at Trapper are routed through one or more sediment ponds. These ponds <br />are designed to control the sediment load in the water discharged from the Trapper permit area. <br />All future sediment ponds to be built at Trapper Mine are designed using hydrologic modeling techniques <br />to predict the peak settleable sediment load during the 10 -year, 24-hour precipitation event. Detailed <br />design plans will be submitted to the Division at least 60 days prior to construction of the structures. <br />Existing ponds which were not designed using these techniques have been re-evaluated to ensure <br />adequacy of each sediment control system. The results of all hydrologic models are presented in <br />Appendix Q, Drainage and Sediment Control Plan. <br />Sediment load in surface water discharged from Trapper Mine is controlled by routing the water through a <br />series of one or more sediment ponds. Sediment ponds have been or will be built in all major drainages <br />at Trapper prior to topsoil removal for advancement of active pits. Sediment pond locations are shown on <br />Map M51, Drainage and Sediment Control. <br />As previously mentioned, all ponds have been designed or confirmed for adequacy, using hydrology and <br />sedimentology modeling. Trapper spent considerable time during the summer of 1986 in discussions with <br />the Division in order to determine the applicable curve numbers and sedimentology parameters for design <br />of drainage and sediment control systems. The agreed upon parameters are shown in Appendix Q, <br />Drainage and Sediment Control Plan, Section XII, Curve Number Determinations, and Section XIII, <br />Sedimentology Parameters. <br />The current drainage and sediment control plan calls for the use of up to 36 sediment ponds either singly <br />or in series over the 5 -year permit term (2013-2017). Design information for each pond is summarized in <br />Table 4.8-6, Sediment Pond Summary Information. Details of all currently designed sediment ponds are <br />included in Appendix Q, Drainage and Sediment Control Plan. <br />4-184 <br />MAY 21 2013 <br />via!�� o i <br />