2007-08-17_PERMIT FILE - C1981035A (14)

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• Runoff from the hillslope above the channel is intercepted by a small ditch (reach 13) and is also taken to the clear water channel, reach 5. The reach 1, intercept ditch will be constructed so that it is nearly adjacent to the top of the waste pile. As the pile elevation increases with time, the ditch will be progressively moved up the hillside. This will occur in stages every three to five years. Reach 3, as shown in Figure 2, is an existing buried pipe which intercepts runoff from the west basin upstream of the mine yard. The end of reach 3 is below the elevated conveyor belt. At this location the reach 4 pipe has been constructed which connects to the reach 3 pipe and transports flow to the reach 5 open channel. The reach 5 open channel conveys all of the clear water diversion runoff the remaining distance to the discharge point in the field at the northeast comer of the mine site. The remaining components of the drainage system, labeled reaches 6-12 on Figure 2, are used in conveying on site yard runoff to the sedimentation ponds. 2.2 Treatment of Contaminated Runoff All runoff generated from the yard area and on the waste pile will be routed to the sedimentation ponds. Three natural areas, two located on the hillside west of the mine entrance and the other on the hillside south of the waste pile, wilt also be collected and routed through the ponds. All of the runoff from these areas will be channeled into the west pond. Only the runoff from the small yard storage area below the offices wilt be • routed to the east pond. The pond hydrology and design is discussed below. Reach 6 is a small open channel which intercepts runoff from the small natural area west of the mine and diverts it via a culvert, reach 9, to the main yard drainage ditch reach 8. Reach 8 leads directly to the west pond. Reaches 7 and 11-are pipe within the yard and reach 12 is a swaie which crosses the main entrance road and moves drainage water to the east pond from the lower yard area. The waste pile is designed with a 2% cross slope extending from the north side (high) to the south side (low}. -Reach 10 is a ditch which runs along the entire length of the waste pile on the south side and intercepts runoff from the pile and from the undisturbed area south of the waste pile and routes it to the southwest corner of the waste pile. At this point the contaminated runoff enters an armored channel, reach 10a, and is transported down the face of the pile and discharged into the yard drainage system. Energy dissipation of the high velocity flow exiting from the channel requires the same structure as described for the outlet of the reach 2 channel in section 2.1 above. In the same manner as the reach 1 ditch, the reach 10 ditch will progressively move up the hillside as the pile elevation increases. • 2 Jaquary 1998