2011-05-23_REVISION - C1981019 (2)

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Colowyo Response - PR3 adequacy No. 2 11 May 6, 2011 proposed worst case disturbance. Other issues that were identified during the review are as follows: • Some of the secondary drainages appear to be improperly located with regard to the post- mining topography. • Disturbed areas are shown downgradient of sediment control ditches. • It is not clear, given the timing of mining and reclamation, how reclaimed areas in the Collom Lite pit will be routed around the temporary spoil pile that will block Collom Gulch. Reclaimed areas in 2016 and beyond in the Collom Lite pit are not shown being diverted around the temporary spoil pile. Discussions with representatives of Colowyo indicate that a sediment pond immediately downgradient of the Collom Lite pit may be proposed. 1. Please review the drainage and sediment control plan over the life of the mine and ensure that all disturbed areas will be routed through the sump/sediment pond system as stated in the permit text narrative under Rule 4. The application remains inadequate. Please review the drainage and sediment control plan over the life of the mine and ensure that all disturbed areas will be routed through the sump/sediment pond system as stated in the permit text narrative under Rule 4. Numerous disturbed areas (topsoil stockpiles excluded) are shown on maps outside of (downgradient) from ditches diverting water through the designed sediment control system. Small areas outside of the primary sediment control system should be addressed as small area exemptions if they will not report to the sump/sediment pond. Please describe in detail, using permit text narrative, maps, cross-sections, and other information as necessary, as to how future reclaimed areas in the Collom Lite pit will be routed around the temporary spoil pile that will block Collom Gulch. Colowyo 's Response: With regard to surface water management for the life of the mine, Exhibit 7, Item 23 Part A has been expanded to address a second timeline scenario that could present a "worst case " loading on the sediment ponds system. This is the condition that will occur in approximately year 2017 when the Collom Lite Pit box cut has been fully developed, the spoil pile is partially constructed and blocks the main drainage, and portions of the Collom X pit are at post-mining topography and in the early stages of reclamation. Under this alternate scenario there are disturbed areas close to the sediment ponds, but a significant portion of the watershed is intercepted by the active pit and by the area immediately above the spoil pile. The SEDCAD modeling included in the expanded Exhibit 7Item 23 shows the system will continue to meet the effluent standards. As discussed in context of a similar comment below dealing with areas that do not report to the sediment pond system, there remain no large areas that do not report to the sediment pond system. As shown on Exh. 7, Item 23, Figure A2, the footprint of the spoil pile in Section 25 has been pulled back to remove the two wings on the northern end that previously lapped over and beyond the ridgeline. The entire spoil pile is surrounded by a perimeter ditch that directs all runofffrom the spoil pile into the downstream sediment control ponds. Colowyo has been