2008-11-07_REVISION - C1996083 ‎(4)‎

• Permit No: C1996083
• IBM Index Class Name: REVISION
• Doc Date: 11/7/2008
• Doc Name: Adequacy Review ‎(Memo)‎
• From: Marcia Talvitie
• To: Joe Dudash
• Type & Sequence: TR56
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver
Colorado 80203 C O L O R A D O
, D IV IS I ON OF
Phone: [phone] RECLAMATION
FAX: [phone] MINING

SAFETY
Bill Ritter, Jr.
Governor
INTEROFFICE MEMORANDUM
Harris D. Sherman
Executive Director
Ronald W. Cattany
Date: 07 November 2008 Divi>ion Director
Natural Resource Trustee
To: Joe Dudash
From: Marcia L. Talvitie, P.E. P4/:?'
Subject: Bowie No. 2 Mine (Permit No. C-1996-083)
Technical Revision No. 56 (TR-56)
Coal Mine Waste Disposal Area - Stability Analysis
Adequacy Review
With its application for TR-56, Bowie Resources, LLC (BRL) is requesting a change in
the allowable side slopes for the Coal Mine Waste Disposal Area No. 2 (CMWDA2).
Previous stability analyses commissioned by BRL had concluded that, in order to achieve
the Division's requisite 1.50 Factor of Safety, the upper portions of CWMDA2 could be
constructed to no steeper than 5H:1 V.
TR-56 presents a follow-up evaluation, conducted for BRL by Buckhorn Geotech, Inc.
(BGI). The report, entitled, "Revised Stability Evaluations for Coal Mine Waste
Disposal Area No. 2", concludes that slopes as steep as 3H:1 V for the upper portions of
CMWDA2 will provide the required Factor of Safety (both during and after construction)
when proper methods of construction are used. The report also recommends that site
conditions continue to be monitored periodically. BGI's conclusion is the result of new
stability analyses based on updated vibrating wire piezometer and inclinometer data
(collected from Nov-2005 through Jul-2008) and on strength testing conducted
previously.
At your request, I have reviewed the report submitted with TR-56. I concur that BGI
successfully demonstrates that CMWDA2 slopes can be safely constructed to 3H:1 V, and
that a minimum Factor of Safety of 1.50 will result, even when using conservative
estimates of site conditions.
Please do not hesitate to contact me with any additional questions you may have
regarding this Technical Revision.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines