REV97591

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 12/2/1998
• Doc Name: WEST ELK MINE TECHNICAL REVISION NO 84 APPLICATION GEOTECHNICAL ADEQUACY SUPPLEMENTAL RESPONSE PERMI
• From: DMG
• To: JIM BURNELL
• Type & Sequence: TR84
• Media Type: D
• Archive: No

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STATE OF COLGiv~vv
DIVISION OF MINERALS AND GEOLOGY
Depanmem of Natural Resources
1313 Sherman Si., Room 215
Denver, Colorado 80203
Phone. [phone]
FAX: p03) 832-8106
DATE: December 2, 1998
TO: Jim Burnell
FROM: Jim Pendleton/
i
RE: West Elk'Mine - Te ical Revision No. 84 Application -
Geotechnical quacy -Supplemental Response
(Permit No: C-80-007)
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DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
dames 5. Lochhead
Executive Director
Michael B. Long
Division Director
On August 14, 1 998, I forwarded a memorandum presenting my geotechnical
adequacy comments regarding Mountain Coal Company's (MCC) TR-84 technical
revision application. TR-84 was filed at the Division's direction to document the
emergency remedial actions taken by MCC to stabilize the massive landslide
occurring beneath its F-Seam surface facilities. MCC's initial submittal represented
a good start. The work accomplished to date appears to be succeeding, although
the landslide has yet to be completely stabilized.
My main geotechnical adequacy concern related to the choice of nomenclature used
by MCC's consultant in assessing the stability of the post-treatment landslide. The
consultant's (Harding Lawson Associates and Barr Engineering .Company) report
implied the landslide was "stable", while documenting continued movement in the
mid and head regions of the landslide mass. I recommended to you that the
Division require MCC to clarify the relative post-treatment improvement of the
landslide's factor of safety (FOS) reported in TR-84, versus the absolute FOS of the
landslide.
MCC has responded by directing Barr Engineering to revise its report. The revisions
carefully distinguish between the documented and projected relative FOS
improvements and the absolute stability of the landslide mass. The Sections of the
report addressing "Stability of Existing Conditions" (§6.0), and "Stability of Long-
Term Conditions (Post-Reclamationl" (§7.0) have been rewritten. In addition, a
detailed supporting discussion has been added as "Appendix F" to the report.
These revisions and additions precisely explain MCC's position that the stability of
the landslide mass has been improved enough by treatments effected to date to
prevent catastrophic failure. Further, they theoretically evaluate additional
improvement in FOS expected to continue to result from past treatments and
additional proposed future stabilization treatment methodologies.