2017-06-09_REVISION - M1980244

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 6/9/2017
• Doc Name: Adequacy Review Response #2
• From: CC&V
• To: DRMS
• Type & Sequence: TR89
• Email Name: TC1
• Media Type: D
• Archive: No

Technical Memorandum ■
Cripple Creek&Victor Gold Mine ■
SGVLF Stability Evaluation—Nonagglomerated Tailings
NewFields Job No.475.0106.009
1 June 2017
saturated or can soften during shaking. For the SGVLF, none of the materials are considered to
be strain softening.
The PGA used in the current evaluation was based on a review of publically available
information regarding the seismic hazard at the site using the United States Geologic Survey
(USGS) interactive deaggregations tool. The updated PGA was listed 0.11g for the 2,475-year-
return seismic events, respectively. NewFields considers this an appropriate risk level for
closure conditions and the current understanding of the seismic region. The output graphic
from the seismic hazard analysis identifying the PGA, mean earthquake magnitude, and mean
rupture distance is presented in Attachment B.
The current evaluation applied a one-third reduction to the PGA for kh which we consider
reasonable and conservative based on the recommendations of Hynes-Griffin and Franklin
(1984).
3.2 Model Development
Both static and pseudostatic loadings were evaluated for two cross-sections. The first section,
Section A, extends from the top of the VLF southwest to the process solution storage area
(PSSA). The second section, Section B, was chosen along the steepest slope of the VLF. Based
on our understanding of the facility geometry, the slopes were modeled with the following
geometric properties:
A maximum heap elevation of 10,450 feet above mean sea level (amsl);
Elevation at the toe of the heap at 9,450 feet amsl;
Lift heights of 100 feet;
Intermediate bench widths of approximately 130 feet;
5- The bench face angle was considered to be 1.4H:1V (approximate angle of repose);
The overall facility slope (compound slope) was considered to be 2.5H:1V;
Side slopes of the VLF are considered to be 1.6H:1V;
The heap leach material is considered perfectly homogenous;
The facility was modeled with a 540-foot setback from State Highway 67; and
The locations of sections analyzed for the stability assessment are shown on Figure 1.
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