2013-12-17_PERMIT FILE - M2013081 (7)

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Table G -1- Runoff Table As shown in Table G -1 above, there is more than enough capacity in both the mining pits and above the water level in the reclaimed lakes to contain the runoff that drains to them. The net result effect on the overall drainage of the site is a decrease in the runoff that leaves the site. The runoff captured by the pit during mining will either work its way through the alluvium and join the local ground water regime or be pass through the pit dewatering system before discharge into the local wetlands and water bodies. The dewatering system provides sediment control through both the placement of the pit pump several feet below the active pit floor and a sediment pond. Runoff that flows into the reclaimed lakes after mining will join the local groundwater regime. Runoff that drains offsite in both the mining and reclaimed cases is from undisturbed areas, 2. Hydrology and Sediment Control for Mining The two main potential sources of sediment the Tomichi Pit can produce during mining are: 1. Sediment from mine dewatering a. Control: Pit pump placed three feet below the active pit floor, and all pit water passes through a sediment pond prior to discharge. Dewatering trenches feed the pump. See Map C -2. 2. Surface runoff from disturbed areas a. Control: All disturbed areas are either immediately vegetated or drain to the mine pits. Small control berms will be built along the sides of areas stripped of topsoil to keep surface runoff draining to the mining pit. By having all surface runoff pass through the mining pit, which then passes through the sediment ponds, the sediment will not discharge from the site. Tomichi Pit, December 2013 G -4 CN Area acres Runoff acre -ft Baseline 74 208.96 7.79 Mining Drains to Pit 78.9 183.88 9.78 Mining (Pit Capacity) 2,483.07 Mining Leaves Site 74 25.08 0.94 Reclaimed Drains to Lake 80.5 183.88 10.87 Reclaimed Excess Lake Capacity) 871.38 Reclaimed Leaves Site 74 25.08 0.94 As shown in Table G -1 above, there is more than enough capacity in both the mining pits and above the water level in the reclaimed lakes to contain the runoff that drains to them. The net result effect on the overall drainage of the site is a decrease in the runoff that leaves the site. The runoff captured by the pit during mining will either work its way through the alluvium and join the local ground water regime or be pass through the pit dewatering system before discharge into the local wetlands and water bodies. The dewatering system provides sediment control through both the placement of the pit pump several feet below the active pit floor and a sediment pond. Runoff that flows into the reclaimed lakes after mining will join the local groundwater regime. Runoff that drains offsite in both the mining and reclaimed cases is from undisturbed areas, 2. Hydrology and Sediment Control for Mining The two main potential sources of sediment the Tomichi Pit can produce during mining are: 1. Sediment from mine dewatering a. Control: Pit pump placed three feet below the active pit floor, and all pit water passes through a sediment pond prior to discharge. Dewatering trenches feed the pump. See Map C -2. 2. Surface runoff from disturbed areas a. Control: All disturbed areas are either immediately vegetated or drain to the mine pits. Small control berms will be built along the sides of areas stripped of topsoil to keep surface runoff draining to the mining pit. By having all surface runoff pass through the mining pit, which then passes through the sediment ponds, the sediment will not discharge from the site. Tomichi Pit, December 2013 G -4