REV07535

• Permit No: M1980244
• IBM Index Class Name: Revision
• Doc Date: 8/6/1998
• Doc Name: PAD 1 SLOPE STABILITY EVALUATION
• From: GOLDER ASSOCIATES INC
• To: CRIPPLE CREEK & VICTOR GOLD MINING CO
• Type & Sequence: TR27
• Media Type: D
• Archive: No

Golder Associates Inc. • III I II I II I II IIII III • ~~M~~
44 Union Boulevard. Suite 300 999 /'~~ ptr
Lakewootl, CO USA 80228 Wl~i..i
' Telephone [phone] c ~S.Ot+t ar ~`as+
Fax [phone] ~.aa~
' July 23, 1998 Our Ref.: 983-2348.160
' Cripple Creek & Victor Gold Mining Company
' 2755 State Highway 67 RECEIVED
P.O. Box 191
Victor, Colorado 80860
' AUG 6198
Attention: Mr. Ron Roberts
' DIV. OF MINERALS
RE: PAD NO. 1 SLOPE STABILITY EVALUATION 8 GEOLOGY
Dear Mr. Roberts,
' The Cripple Creek & Victor Gold Mining Company (CC&V) has asked Golder Associates
' Inc. (Golder) to evaluate the impact of revising the ore sideslopes on the stability of
existing Phase I and II valley leach facilities for Pad No. 1. This letter report summarizes
the stability analysis for overall sideslopes of 1.6H:1V and a maximum ore depth of
' 320 feet.
STABILITY
' Slope stability was evaluated according to Spencer's Method for wedge-shaped failures. The
method of analysis considers potential failure masses as rigid bodies divided into adjacent
' regions or "slices," separated by vertical boundary planes and is based on the principle of
limit equilibrium; i.e., the method calculates the shear strengths which would be required to
just maintain equilibrium, and then calculates a "factor of safety" (FOS) by dividing the
' available shear strength by the required shear strength. Consequently, the FOS indicates the
ratio by which the available shear strength exceeds, or falls short of, that required to maintain
equilibrium. Therefore, a FOS in excess of 1.0 indicates stability and those less than 1.0
' indicate instability, while the greater the rnathematical difference between a FOS and 1.0, the
larger the "margin of safety" (for a FOS in excess of 1.0), or the more extreme the likelihood
' of failure (for a FOS less than 1.0).
For this study, stability analyses were conducted using XSTABL, a commercially available
computer program, with input parameters as presented in this report. For each failure mode,
the XSTABL critical surface search routine was used to determine the least stable failure
surface. The program automatically iterates through a variety of potential failure surfaces,
' calculates the FOS for static and pseudo-static conditions for each surface according to
Janbu's Simplified Method, and selects the surface with the minimum FOS, commonly
referred to as the critical surface. The FOS of this critical surface was then evaluated
' according to Spencer's Method. Static analyses were conducted with no applied horizontal
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