REP24039

• Permit No: C1992080
• IBM Index Class Name: Report
• Doc Date: 10/23/1996
• Doc Name: SLOPE STABILITY ANALYSIS SANDSTONE SLOPE CARBON JUNCTION MINE PN C-82-54
• From: DMG
• To: HARRY RANNEY
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

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999
STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Deparhnenl of Natural Resources
1713 Sherman 51.. Room 215
Denver, Culurddu 80201
Phone: U03) 866-3567
FAX: [phone]
DATE: October 23, 1996
TO: Harry Ranney
FROM: Jim Pendleton
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RE: Slope Stab~ity An~Iysis - Sandstone Slope
Carbon Ju tion ine (Permit No: C-82-054)
II~~~
DEPARTMENT OF
NATURAL
RESOURCE
Roy Romer
Governor
lames S. Lochhead
Executive Director
wtichael 8. Long
Division Director
I have reviewed the slope stability analysis completed by Lambert
& Associates, Inc., consultant to the Carbon Junction Mine, which
you forwarded to my attention. This analysis evaluates the
predicted slope stability of a four foot thick soil mantle applied
to the existing sandstone dip slope exposed at the Carbon Junction
Mine. This dip slope, which dips at 25 to 30 degrees from
horizontal, is the remnant seam floor exposed by the removal of the
resource coal seam.
Lambert & Associates performed an infinite slope mathematical
analysis of the proposed treatment. While this is a relatively
simplistic approach to stability analysis, it is appropriate for
the situation at hand. Lambert and Associates' analysis concludes
that the four foot thick soil mantle will remain stable, if it
remains dry. If, however, the soil were to become moistened, it
will fail ("slump"). I agree with their conclusion. Since
experience leads me to suspect that this mantle of topsoil will
eventually be moistened, I conclude it will eventually fail. I
also find their choice of analytical methodology to be appropriate
for the proposed reclamation activity.
Frankly, this is the most asinine reclamation proposal it has been
my pleasure to review in my past 16 years and nine months with the
Division. The existing sandstone dip slope is stable. It is also
reminiscent of the natural "flatiron"-like sandstone dip slopes in
the immediate valley surroundings. To attempt to artificially
place a thin mantle of valuable soil resource on this slope will
accomplish no benefit to the reclaimed environment. The mantle
will fail during the first spring melt or torrential thunder storm.
When it fails, it will probably cause a portion of the soil
resource to be lost. It may also subject the downslope area to
additional sediment production. Conceivably, it might also
represent a risk to human health and safety.