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C-1981-010 PR-06 <br />2nd Engineering Adequacy Review <br />02 July 2009 <br />Page 2 of 4 <br />Please provide a description of the benching activities proposed for the steeper side <br />slopes that exist within the Horse Gulch Fill area. <br />Response: The AAI Horse Gulch Fill Stability Analysis report has been revised to <br />include a description of benching activities proposed for the steeper side slopes that <br />exist within the Horse Gulch Fill Area (page 26 and Figure 29). <br />Item resolved - no further action is required. <br />4.09.1(11) - Inspection - The AAI Report on the HG Fill discusses inspection of <br />construction of that fill and the underdrain, but inspections are not mentioned in either the <br />K-Pit Buttress stability analysis or within the permit test. <br />Please provide specific information within the pages of the Permit that thoroughly <br />addresses the requirements of Section 4.09.1(H) regarding inspection of construction of <br />the Horse Gulch and K-Pit Buttress Fills. <br />Response: The inspection of fills is now addressed on pages 3-40b and 3-40c. In <br />addition, Section 5.0 Construction Inspection has been added to AAI's K-Pit Buttress <br />Fill Stability Analysis. <br />Item resolved - no further action is required. <br />4.09.1(14) requires that the foundation and abutments of the fill shall be stable under all <br />conditions of construction and operation. Maps have been provided which depict the <br />mining plan and post-mining topography, and the method of construction of each fill is <br />described, e.g. dragline and/or truck dump. Very little information has been provided <br />regarding the anticipated phasing (including length of time required) for the dragline <br />portion of HG Fill to be constructed, or construction of K-Pit Buttress, or construction of <br />the remainder of the HG Fill. <br />Please provide additional detail about the timeline and phasing of the construction of the <br />HG Fill, in particular, including a discussion of the stability of the fill under all <br />conditions of construction and operation. <br />Response: Section 4.4 of AAI's Horse Gulch Fill Stability Analysis report has been <br />revised to include discussions of phasing of the construction of the Horse Gulch Fill <br />and fill stability during construction and operation. <br />Item resolved - no further action is required. <br />4. 4.09.2(2)(d) requires that in constructing the underdrains, no more than 10 percent of the <br />rock may be less than 12 inches in size and no single rock may be larger than 25 percent <br />of the width of the drain. Figure 24 and the Appendix A Horse Gulch Underdrain detail <br />of the AAI report indicate that no more than 10 percent of the rock will be less than 10 <br />inches in size.