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Mr. Jack Henris <br />July 13, 2016 <br />Page 8 <br />m:\min\tc1\_teller\m-1980-244 cc-v\am-11\m-80-244-am-11maincommentr12016-07-13.docx <br />analyses”, but of the 10 cross sections evaluated (reference Table 6-2 and Figure 6- <br />1), only two (WH-3 and GH-4) consider highwall stability near Teller Co Rd 82. <br />Please comment on whether or not these recommendations are intended to satisfy <br />the requirements of Rule 6.5. <br />31. Appendix 5 – Factors of Safety. The implication from this report (Paragraph 1.3.4, Table <br />6-2, and Figure 6-10) is that a factor of safety (FOS) of 1.2 is universally accepted. <br />a. If a slope failure has the potential for off-site impacts or damage to a structure (e.g., <br />Teller Co Rd 82, Squaw Gulch VLF near the North Cresson Mine/Schist Island, and <br />possibly the Mollie Kathleen tourist mine), the minimum FOS presented in DRMS <br />Table 1 (reference Comment No. 20 above, then the Division requires a minimum <br />FOS = 1.3 (assuming strength measurements resulting from multiple tests have been <br />performed; otherwise a minimum FOS of 1.5 is required for critical structures, such <br />as the Globe Hill Pipe zone where Section 1.2.3, p. 1-3 states “shear strength was <br />estimated based on previous experience in similar type materials”). Based on Figure <br />1-1, it appears the higher FOS is required for Sectors 2, 10, 12, 14, and possibly 4. <br />Please confirm the minimum FOS in the vicinity of critical structures is consistent <br />with DRMS Table 1 and include critical structures on Appendix 5 figures. <br />b. The last paragraph on p. 4-9 cites Wiles (2000) suggesting the “coefficient of <br />variation for rockmass strength estimation may be 25 to 35 percent”. Given this <br />variability in an anisotropic fractured system, the Division is concerned that despite <br />the numerous tests performed to estimate rock strength parameters, this expected <br />variability, an FOS of 1.5 may be appropriate. Please provide appropriate rationale <br />if you disagree with the Division requiring a FOS of 1.5 in the vicinity of critical <br />structures (e.g., Co Rd 82, SGVLF). <br />32. Appendix 5 Geotechnical Slope Recommendations, p. 5-8, Section 5.4.1. The report states <br />“Current design interramp angles do not meet the required 80% reliability in Sectors 1, 2, 6 <br />and 7”. <br />a. Please provide a source and rationale for the 80% reliability requirement. <br />b. Is this 80% reliability for slope stability or catch bench functionality? <br />33. Appendix 5 Geotechnical Slope Recommendations, Table 5-1. The table indicates Bench <br />Analysis Sectors 1, 2, 6, and 7 have design angles steeper than the recommended interamp <br />angle. Please explain how this will be corrected or mitigated. <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