REV89098

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 11/13/1998
• Doc Name: WEST ELK MINE RUN OF MINE EXPANSION PAD DESIGN REVISION MR 256 GEOTECHNICAL ADEQUACY PN C-80-007
• From: DMG
• To: JIM BURNELL
• Type & Sequence: TR87
• Media Type: D
• Archive: No

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STATE OF COLGi~~v
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman 51., Roam 215
Denver, ColoraAo 80207
Phone: U03) 866-3567
FAX: [phone]
DATE: November 13, 1998
TO: Jim Burnell
FROM: Jim Pendleton
_. _,
~.. U.i _
RE: West Elk Mine -Run- -Mine Expansion Pad Dcsign Revision -
M.R;;No. 2~6 - otechnical Adequacy (Permit No: C-80-007)
I~~~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Ramer
Governor
Wme~ S Lochhead
Executive Director
Michael B. Long
Division Dneaor
West Elk Mine received approval to expand their Run-of--Mine coal storage pad as MR No. 240.
In November of this year you determined that Mountain Coal Company had constructed a
portion of the out slope at 1.38H:l.OV, rather than the approved slope gradient of 2.OH:1.OV.
The Division directed MCC to reconfigure [he slope or demonstrate that the slope attained the
required static safety factor of >_ 13. MCC chose to complete a stability analysis of the as-built
steepened out slope.
Barr Engineering Company, consultant to MCC on many of the recent slope stabilization
projects at the West Elk Mine, completed the required analysis. The analysis was completed
using a combination of material properties derived for the original design analysis and material
propehies obtained through additional sampling and laboratory testing. The analysis reflected
the lack of ground water encountered during the construction and related auger investigations of
the foundational vicinity. The stability analysis, which appears to have been conducted in
accordance with acceptable methodology, determined that the steepened out slope has a static
factor of safety of 1.31. As such the as-built oLlt slope is acceptable.
The stability analysis assumes non-saturation of the foundational bedrock and soils, the storage
pad till, and the cut slope bedrock and soils above the pad. Because the safety factor of the out
slope is slightly above the required minimum, it is important that the materials involved remain
unsaturated. For this reason I believe it is appropriate to impose hvo monitoring requirements
Llpon approval oY M.R. - 256.
(1) MCC should install and monitor three (3) piezometers at the crest of the outslope. These
piezometers should be installed to refusal in bedrock. The piezometers should be
monitored to determine if any ground water is present within or beneath the fill slope.
(2) MCC should install slope stability monument profile lines on the out slope of the
expansion to verify [hat the slope is stable. These profile line may include the
piezometers as their upper members. MCC may install simple line -of--sight monuments
similar to [hose previously installed and monitored a[ numerous locations throughout