REV91274

• Permit No: M1980244
• IBM Index Class Name: Revision
• Doc Date: 11/25/1998
• Doc Name: CC&VG CRESSON PROJECT GEOTECHNICAL FINDINGS AUGUST 1998 AMENDMENT 7 APPLICATION PN M-80-244
• From: DMG
• To: BERHAN KEFFELEW
• Type & Sequence: AM7
• Media Type: D
• Archive: No

• • iii iiniiiiiiiu iii
STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman 8r., Room 215
Denver, Colorado 80?03
Phone: [phone]
FAx: [phone]
DATE:
TO:
FROM:
RE:
Seismicity
Novcntber 25, 1998
Berhan Keffelerv
Jim Pendleton
CCCQC
Augu
~~~~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
~ James 5. Lochhead
' Executive Diceuor
~// ~ Michael B. Long
Division Director
- Geotechnical Findings -
~Cmendment No. 7 Application
(Permit No: M-80-244)
CC&VG requested that a revised Peak Ground Acceleration (PGA) coefficient be accepted by the
Division for use by CC&VG in preparing future pseudo-static stability analyses at the Cresson project
The Division reviewed the seismogenic analysis prepared by Golder Associates The Division also
obtained the services of Dr. W Pat Rogers, retired of the Colorado Geological Survey, to complete an
evaluation of the Golder report. As a res«It of these evaluations, the Division will accept thr, revised 0.088
PGA for application to structures a[ the Cresson project classified as "standard" under the terminology of
the Unitied Building Code (UBC) seismic design regulations. However, for application to strictures
classifed as "essential" or "hazardous" structures under the terminology of the I;BC scisl;uc design
regulations, the Division will require [hat [he currently approved PGA of 0.148 be used m conrple[ing
pseudo-static stability analyses. Roads, mine highwalls, overburden storage structures, diserion
structures, and the valley leach facility after detoxification, are examples of UBC classified "standard"
structures. In the opinion of the Division, the valley leach facility prior ro detoxification is an example of
a UBC classified "hazardous" structure.
CC&V disagrees with the Division's characterization of the valley leactl facility as "hazardous" Further,
CC&V suggests that because [he valley heap leach is a "non-occupied earthworks structure", located in a
rural area, with extensive buffer area to prohibit public access, [ha[ the structure is not "hazardous".
CC&V has expressed a wish to pursue the appropriateness of the Division's decision regarding UBC
classification of the operation valley leach facility outside the framework of Amertdmertt No. 7. CC&V
tttay readdress [Iris topic at their discretion.
Valley Leach Facility Phase III Expansion
C&VG proposed to increase the maximum ore depth from 320 feet to 504 fee[, with overall 1.6H:1.OV
sideslope in all areas around the perimeter of the valley leach facility with [he exception of the area up
gradient of the Pltase II Toe Berm which area will remain at a 2.SH:I.OV sideslope. Tltis expansion itas
been developed to increase the capacity of the valley leach facility to a total of approximately 115,000,000