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Mr. Jack Henris <br />July 13, 2016 <br />Page 11 <br />m:\min\tc1\_teller\m-1980-244 cc-v\am-11\m-80-244-am-11maincommentr12016-07-13.docx <br />failure under the ECOSA and statements in the Hydrogeochemistry Evaluation (Vol <br />II, paragraph 3.6.6) “under high infiltration conditions, some of the infiltrating <br />precipitation water will flow along the surface of the boulder till, and emerge at the <br />northern downhill tow [sic] of the ECOSA” suggest a likelihood of a saturated <br />colluvium. Please factor this into the slope stability analyses. <br />41. Appendix 6, p. 4, Bedrock. The assumed φ (friction angle) and cohesion values are 45 <br />degrees and 5,000 psf (~35 psi), respectively. Based on a comparison of Drawing C-7, <br />District Geology (Vol. I) and the ECOSA location on Figure 2 (amended AM-11) the <br />possible bedrock underlying the ECOSA is phonolite, feldspar bearing – plagioclase <br />phonolite, and/or Cripple Creek lapilli breccia. A comparison of mean strengths in Table <br />6-1 of Appendix 5 (Vol. III) suggest the cohesion value used is conservative (i.e., less than <br />that obtained from testing), but the 45 degree friction angle is much higher than the highest <br />mean value (for RQD = 90%) in Table 6-1. The level of uncertainty for this particular <br />bedrock material suggests the use of strength parameters in the medium range (e.g., RQD = <br />50 %) and FOS from DRMS Table 1 for “Generalized, Assumed, or Single Test Strength <br />Measurements”. Please use consistent strength parameters or further justify the use of 45 <br />degrees and 5,000 psf. <br />42. Appendix 6, Paragraph 2.4, Stability Evaluation Results. The ECOSA is an engineered <br />environmental protection facility (EPF). The analyses for Sections 1 and 2 (considered <br />critical structures) need to be re-evaluated based on Comment Nos. 40 and 41 above. The <br />Section 3 (non-critical structure as slope failure would not be expected to directly have an <br />offsite impact) pseudo‐static analysis, resulted in a FOS of 1.0. This is unacceptable for <br />during operations or after reclamation. The Division will not approve an increase in the <br />height of the ECOSA if appropriate FOS’s (based on DRMS Table 1) cannot be <br />achieved. <br />43. Appendix 6, Figure 5, Section 3. Please explain why the east slope is steeper (2.5H:1V) <br />than during operations (2.9H:1V). <br />44. Appendix 7, Table 2 – Runoff Coefficients. This table indicates 100 percent runoff from <br />precipitation for areas that are actively being leached or lined, but with no ore covering the <br />liner. This is a very reasonable assumption, but it is unclear where runoff peak flows are <br />directed such that they are controlled and contained within the VLF. Please explain how <br />the runoff from the 100-year, 24-hour precipitation event is controlled and contained within <br />the VLF. <br />45. Appendix 7, PSSA Capacity and Pumping Rates. The first paragraph states “Minimum <br />operating volumes were not provided for PSSA 5 of the Arequa Gulch site or for the Squaw <br />Valley PSSA”. Why were these values not provided? <br />46. Appendix 7, PSSA Capacity and Pumping Rates. The last paragraph states “As a criterion <br />for evaluating adequacy of storage in each facility, five feet of freeboard was required to be <br />maintained in each PSSA”. Does this five feet of freeboard correspond to the maximum 80