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RESPONSE. The 80 percent catch-bench reliability is for catch bench functionality <br /> only (not for global slope stability). Normally, catch bench reliability is designed <br /> anywhere from 50 to 90 percent depending on site-specific operation requirements. The <br /> catch bench reliability does not affect the global slope FOS. <br /> 33. Appendix 5 Geotechnical Slope Recommendations, Table 5-1. <br /> • The table indicates Bench Analysis Sectors 1, 2, 6, and 7 have design angles steeper <br /> than the recommended interramp angle. Please explain how this will be corrected or <br /> mitigated. <br /> RESPONSE. In order to obtain adequate catch-bench performance the interramp slope <br /> design should be modified to the angles and bench configurations listed in Table 1-1 in <br /> the CNI report. This table combines the recommendations from the bench-scale and <br /> global stability analysis on a sector-by-sector basis. <br /> 34. Appendix 5 Section 6.3, Global Stability Analysis Results (p. 6-4).This paragraph states a <br /> FOS of 1.2 is appropriate.As stated above in Comment Nos. 20 and 31 where critical <br /> structures are involved, an FOS of at least 1.3 (for high confidence strength parameters)and <br /> 1.5 (for low confidence strength parameters, i.e., "coefficient of variation for rockmass <br /> strength estimation may be 25 to 35 percent"). Please provide: <br /> • Analyses showing adequate FOS (per DRMS Table 1 above)exists to the edge of <br /> Right-of-Way for Teller Co Rd 82, <br /> RESPONSE. Teller Co. Road 82, ECOSA, SGVLF, and the Mollie Kathleen tourist <br /> mine has been added to an updated Figure 6-1 (Attachment 8). Cross sections WH-3 <br /> and GH-4 are in ideal locations to analyze potential interaction between the proposed <br /> mine slopes and Teller Co. Road 82. Teller Co. Road 82 has been added to Figures 6- <br /> 17, 6-18, 6-29, and 6-30 (Attachment 8). <br /> Section GH-4 is on the northeast wall of the proposed Globe Hill area of the WHEX <br /> mine. Teller Co. Road 82 is located approximately 150 feet behind the designed crest <br /> of the slope as can be seen in Figures 6-17 and 6-18(Attachment 8). Two different <br /> failure mechanisms were analyzed, as described below: <br /> -The critical slip surface which goes from the toe to crest of the slope has a FOS <br /> of 1.52. This is greater than the criterion of 1.5 for failure mechanisms that <br /> may interact with critical structures. <br /> •A second failure mechanism was analyzed beneath the ramp near the toe of <br /> the slope in the altered Globe Hill pipe material. This lower failure mechanism <br /> has a FOS of 0.96 with the 03-17-2015 NA mine design. CNI recommends <br /> that the interramp slope angle below the ramp be reduced to 40 degrees in <br /> order to obtain a FOS of 1.20 for the lower failure mechanism. We believe that <br /> a FOS criterion of 1.20 is appropriate for this failure mechanism since it does <br /> not interact with any critical structures and is wholly contained within the <br /> mining area. <br /> Section WH-3 is on the northeast wall of the WHEX mine. Teller Co. Road 82 is <br /> located approximately 200 feet behind the designed crest of the slope as can be seen in <br /> Figures 6-29 and 6-30(Attachment 8). The critical slip surface has a FOS of 1.84, <br /> which is greater than the criterion of 1.5 for failure mechanisms that may interact with <br /> critical structures. <br /> Page 15 of 30 <br />