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Fourth Adequacy Response 112(d)-1 Application, Amended CN-01 <br />Wildcat Mining Corporation May Day Idaho Mine Complex <br />bottom width in Figure 1. Please make corrections such that the design calculations are <br />consistent with the design drawing. Also clarify on the drawing (Figure 1) whether the <br />proposed contours are finished grade (i.e., top of riprap) or subgrade (i.e., top of <br />excavated surface on which the filter fabric is to be placed). <br />Comments: Figure 1 has been redrafted to provide specification clarity. <br />10. It appears from Figure 1 that the invert of the proposed channel is approximately 10 feet <br />higher than the low spot on the Chief Adit bench. This is not acceptable. The <br />reclamation drainage channel invert should match the pre-disturbance invert elevation. <br />This will prevent a failure of the berm on the north side of the channel from allowing <br />runoff to report to the adit and/or the scour of bench material; and reduce the potential for <br />the outfall of the reclaimed channel from head cutting upstream. <br />Comments: Figure 1 has been redrafted to provide clarity. <br />11. Figure 1 does not show the existing natural upstream channel invert or centerline. Please <br />add this to the drawing so the Division can evaluate the alignment between existing and <br />proposed channel bottoms. The drawing should also indicate the extent of disturbance. <br />Comments: A field survey will be required to address this comment. <br />12. The section presented in Figure 2 indicates there is an adverse gradient from Station 0+00 <br />to about 0+20 where ponding will occur. The reclaimed channel should not be allowed to <br />pond unless it can be demonstrated that this was the natural condition prior to the <br />disturbance. <br />Comments: Figure 1 has been redrafted to provide clarity. <br />13. The section from Station -0+80 to 1+07.07 shows a slope of approximately 1.611:1 V (or <br />60 percent). This suggests this is material placed at angle of repose and likely mine <br />waste. Again, the proposed invert should match the pre-disturbed channel invert or the <br />applicant needs to demonstrate to DRMS that this was the pre-disturbance channel slope. <br />DRMS will require protecting this steep section (if it was naturally this steep) unless it <br />can be demonstrated to be non-erodible material, such as bedrock. If the channel was this <br />steep and non-erodible, an energy dissipation structure is required at the bottom, which is <br />not shown on Figure 2. Please extend the section line to meet the natural undisturbed <br />channel invert. <br />Comments: Figure 1 has been redrafted to provide clarity. <br />14. Standard drafting convention for section lines is that the prime (') A - A' appears on the <br />right end of the line in order to make it clear from which direction the viewer is observing <br />the section. <br />Comment: Comment noted. <br />6/6/2011 <br />14