REV96947

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 6/14/1994
• Doc Name: WEST ELK MINE ADEQUACY REVIEW TR 69 LONE PINE GULCH VENTILATION FAN BENCH PN C-80-007
• From: DMG
• To: CHRISTINE JOHNSTON
• Type & Sequence: TR69
• Media Type: D
• Archive: No

Memo to Christine Johnston
Mountain Coal T.R. 69 Adequacy
page 2
each of these instances Mountain Coal has had to submit proposed
technical revisions to treat and repair the stability problems. In
some instances, such as the conveyor, repeated treatments have been
necessitated. As Mountain Coal has observed in every instance,
these remedial treatments have been expensive :•
Mountain Coal's T.R. 69 application contains a stability analysis
prepared by Envirocon, Inc., consultant to Mountain Coal. The
analysis applies standard methodology to evaluate the likelihood of
a rotational failure in the immediate vicinity of the fan bench and
the fan bench faceup. The analysis uses strength values previously
determined at the site. No reference is given to allow me to
determine where and when the samples were obtained or what
methodology was applied in determining their mechanical parameters.
None-the-less, the strength parameters chosen appear representative
for the materials encountered in the bore holes and modeled in the
analysis. That is to say, representative values for unsheared
samples of these earthen materials. The modeled bedrock
configuration suggests an excavated foundational benched pocket in
stable bedrock. Unfortunately none of these assumptions appear to
be appropriate for the chosen site.
As a portion of my review I examined our stereographic aerial
photography of Lone Pine Gulch. Specifically, I examined
photography obtained in 1980, 1982 and 1993. My examination
discerned topographic artifacts which I interpret to be indicative
of repeated, shallow and deep-seated slope failures (landsliding)
throughout the majority of the northeast facing slope of Lone Pine
Gulch. In the immediate vicinity of the proposed ventilation fan
facility the imagery suggests a large prehistoric landslide complex
has been the scene of more modern historic landsliding. The
coincidental bench and hollow landform in which Mountain Coal
proposes to place the ventilation fan and attendant facilities
appears to be the result of a moderately-sized modern rotational
landslide. The appearance of the landslide body suggest its
probably less than fifty years old. I have attached a sketch of
the aerial photo landslide landform boundaries.
Simply stated, the proposed site for the ventilation fan
installation appears unsuited for the proposed use. I suspect that
at the least the facility will be plagued by recurrent operational
problems as progressive "slope and foundational adjustments" occur.
Large fans and their gyroscopic high RPM electric motors do not
respond well to abrupt changes in attitude. Larger landslides or
rockfalls could render the fan and its portal and shaft inoperable,
representing a significant safety threat to mine manpower.
Finally, appropriate reclamation of the site, including elimination
of the fan bench highwall at a minimum, may be infeasible.