2016-09-26_REVISION - M1980244

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 9/26/2016
• Doc Name: Adequacy Review Response
• From: CC+V
• To: DRMS
• Type & Sequence: AM11
• Email Name: TC1
• Media Type: D
• Archive: No

RESPONSE: The ECOSA is now labeled on the revised attached Figures 6-1, 6-25,
and 6-26(Attachment 8). The portion of the ECOSA above section WH-1 does not have
the potential to interact with either Grassy Creek or Teller Co. Road 81. Therefore, CNI
advocates that the western portion of the ECOSA not be classified as critical structure
since it is wholly contained within the mine site and has no potential for interaction with
off-site structures. The final mine plans call for the WHEX mine to be backfilled with
overburden material. Once the pit is backfilled the FOS value will be greater than 1.5
as the slope will be fully buttressed with rock fill material. As such, section WH-I would
only temporarily be permitted to have a FOS value below 1.5, but would have a FOS
greater than 1.5 for long-term reclamation after the WHEX mine is backfilled.
• Show/label the ECOSA on Figures 6-1, 6-25 and 6-26,
RESPONSE. The ECOSA is now labeled on the revised attached Figures 6-1, 6-25,
and 6-26(Attachment 8).
37. Appendix 5 Section 6.3.11, Figures 6-1 and 6-18. Based on Figure 6-1, it appears Section
WH-3 (northeast side of the WHEX mine) may include a portion of Teller Co Rd 82. The
Division considers this road a critical structure and requires the road be shown on Figures
6-1 (in plan view) and 6-30 (in section). Section 6.3.11 references Figures 6-28 and 6-29 for
the WH-3 geology. The reference to Figure 6-28 is incorrect as that is for WH-2. Please
provide the following:
• Assurance that the appropriate FOS at the edge of the Co Rd Right-of-Way is
achievable (reference DRMS Table 1 above),
RESPONSE: See response to question 34 (first bullet point) above.
• Show Teller Co Rd 82 on Figures 6-1, 6-29 and 6-30.
RESPONSE: See response to question 34 (first bullet point) above.
38. Appendix 5 Table 6-2.
• Only four of the 10 cross sections analyzed have an acceptable FOS for global stability.
Please discuss how the mine intends to achieve stable highwalls,keeping in mind FOS
standards listed in DRMS Table 1 are required for at least sections GH-4, WH-1 (both
with respect to CR 82) and WH-3 (respect to ECOSA).
RESPONSE. In order to obtain adequate global slope performance, the interramp
slope design should be modified to the angles and bench configurations listed in Table I-
I of the CNI report. This table combines the recommendations from the bench-scale and
global stability analysis on a sector-by-sector basis.
39. Appendix 5 Figure 6-1. It appears the NW corner of the North Cresson (Globe Hill) mine
intersects Poverty Gulch which appears to be confirmed based on discussions in Volume
IV, Appendix 10 (pp. 8— 11,North Cresson and Poverty Gulch Storm Water Management).
This raises two concerns:
• Although flow is infrequent in Poverty Gulch,the proximity(if the flow is not actually
intercepted) suggests the rock mass may not be accurately described as completely
"drained"as stated in paragraph 6.2.2, Hydrology (p. 6-3). Please analyze a cross
section roughly perpendicular to Section GH-4 through the NW corner of the Globe Hill
pit, assuming saturated conditions.
RESPONSE: The new cross section GH-6 was analyzed under fully saturated
conditions. The resulting critical slip surface had a FOS of 1.43 and is presented in
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