REP42889

• Permit No: C1981022
• IBM Index Class Name: Report
• Doc Date: 1/10/1997
• Doc Name: COAL MINE WASTE BANK DESIGN FOR THE SANBORN CREEK MINE PN C-81-022
• From: DMG
• To: BILL CARTER
• Permit Index Doc Type: Waste Pile/Fill Report
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Depanmem of Natural Resources
1317 Sherman St., Room 215
Denver, Calorario 80203
Phone: [phone]
F.4X: 1303) 832-8) Ob
DATE
January 10, 1997
~~~~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
T0:
Bill Carter
lames S. Lxhhead
Eaec uove Director
Michael B. Lonq
Divivon Direcbr
FROM
RE
Jim Pendleton
"Coal Mine~~e Bank Design
Creek Mine" (Permit No:
for the Sanborn
C-81-022)
I have completed a preliminary review of the geotechnical aspects of the
design analysis prepared for Oxbow by WESTEC, which you forwarded to
my attention. During our visit to the proposed waste pile site last fall, I
indicated my willingness to preliminarily review the document, in an
effort to expedite the process.
Design Report & Stability Analysis
WESTEC has done a good job of preparing the design documents and the
accompanying stability analysis. A combination of laboratory analysis and
field blow count conversion was used to develop material strength
properties for the waste and three materials encountered within the site
foundation. All of the analytical techniques and field observations appear
appropriate. The stability analyses, performed for both rotational and
planar failure scenarios project a minimum static slope safety factor of
2.1 for the circular failure mode and 2.3 for planar failure. Corresponding
pseudo static factors of safety are 1.5 for the circular case and 1.8 for
the planar case. As such these safety factors easily satisfy the
requirements of our regulations.
My review of the design report and analysis discerned only one concern.
During our reconnaissance of the site last fall, I mentioned a concern