2008-01-24_GENERAL DOCUMENTS - M1977493

• Permit No: M1977493
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Date: 1/24/2008
• Doc Name: Seismic evaluation
• From: Climax Molybdenum
• To: DRMS
• Media Type: D
• Archive: No

SMITH WILLIAMS CONSULTANTS, INC.
304 Inverness Way South • Suite 490 • Englewood, Colorado 80112-5828
Phone: [phone] • Fax: [phone] • www.goswc.com
January 22, 2008
Catherine A. Clark, P.E.
Chief Engineer
Climax Molybdenum
P.O. BOX 68
Empire, Colorado 80438
Re: Climax 2010 Project
Recommended Seismic Stability Approach
Dear Catherine:
Project 1115
This letter has been prepared by Smith Williams Consultants, Inc. (Smith Williams) for Climax
Molybdenum and provides the proposed technical approach and rationale for evaluating the
seismic stability of the existing Tenmile and Mayflower tailing storage facilities (TSF) for the
Climax 2010 Project. The seismic stability of the TSFs will be evaluated as part of the final
engineering design work and will consider the existing and future TSF configurations.
The proposed approach presented herein to assess the seismic stability of the TSFs is consistent
with the current internationally accepted design philosophy for geotechnical structures such as
dams and other tailing facilities constructed throughout the world. It is proposed that the TSFs
be evaluated for seismic stability under two levels of design earthquake events: the Operating
Basis Earthquake (OBE) for the operational period of the facility and the Maximum Design
Earthquake (MDE) for the post-closure period.
Based on definitions presented in ICOLD (1995) and USACE (1995), the OBE is an earthquake
event that can reasonably be expected to occur within the service life of the project. The
associated performance requirement with an OBE is that the facility will operate with little or no
damage and without interruption of function. The MDE is the maximum level of ground motion
for which a structure is designed or evaluated. The associated performance requirement for an
MDE is that the facility performs without catastrophic failure, such as uncontrolled release,
although severe damage or economic loss maybe tolerated.
The OBE for the Tenmile and Mayflower TSFs will be selected based on the operational life of
the facility and the results of the probabilistic seismic hazards assessment (PSHA) completed for
the site. The MDE will be set equal to the Maximum Credible Earthquake (MCE) (ICOLD,
1995) and will be based on a deterministic assessment for the project site. The parameters for
the OBE and MDE (e.g., peak ground acceleration and return period) will be developed as part
of the detailed design effort and submitted for review pursuant to Rule 7.3.1 (1).
C:\DOCUMENTS AND SETTINGS\roxaneUocal settings\tertiporary intemet files\content.ouUook\a3c4wovg\seismic stability letter.doc