REV96117

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 1/10/1997
• Doc Name: MOUNTAIN COAL CO TR-78 SUPPLEMENTAL LOWER REFUSE PILE STABILITY ADDENDUM 2
• From: DMG
• To: MIKE BOULAY
• Type & Sequence: TR78
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OE MINERALS AND GEOLOGY
Department of Natural Resources
I J 13 Sherman 51., Roont 215
Denver, Colorado 80203
Phone: (3031 R66-3567
FAX: U031 832-8106
DATE: January 10, 1997
TO: Mike Boulay
FROM: Jim Pendleton
~~~~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
lames 5. Lnchhead
Evecmive Director
Michael B. Long
Division Director
RE: Mountain C al Co any - TR-78 - Supplemental
Lower Refuse ile - Stability Addendum #2
(Permit No: C-80-007)
In response to my third set of adequacy comments, dated November 1,
1996, Mountain Coal Company (MCC) commissioned Harding Lawson
Associates (HLA) to revise their amended stability analysis of the
West Elk mine's Lower Refuse Pile reconfiguration. Their second
revised analysis applied an amended perched water table assumption
to their earlier configuration. The soil material strength
parameters and distributions were unchanged, with the amendment of
the perched saturated zone. In completing this analysis, HLA used
the U.S. Army Corps of Engineers "Hydrologic Evaluation of Landfill
Performance (HELP) analytical software to model the perched water
table development within the pile. HELP was developed by the Corps
for the EPA and is considered the definitive analytical software
for such perched water table predictive modeling.
The modeled perched water table configurations appear to have been
appropriately completed. As in the earlier analysis, three
critical cross sections were analyzed. As in the earlier analysis
the waste material was modeled using the worst case assumption,
that of the 10°s fines material. Profile 3 (the east facing slope)
was determined under the projected perched water table
configuration to have a static slope safety factor of 1.65.
The second supplemental submittal has satisfied my earlier concerns
regarding stability of the Lower Refuse Pile at the West Elk Coal
Mine. MCC may continue to place refuse on the remaining portions
of the LRP in accordance with the proposed configuration.
cc: David Berry
Susan McCannon
doe: M:\COAL\JAP\MCCLRP3.SAN
JP/jP