2009-05-29_REVISION - C1996083 ‎(10)‎

• Permit No: C1996083
• IBM Index Class Name: REVISION
• Doc Date: 5/29/2009
• Doc Name: Adequacy Comments ‎(Geotechnical)‎ Memo
• From: Marcia Talvitie
• To: Joe Dudash
• Type & Sequence: TR61
• Email Name: JJD
• 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
Phone: [phone]
FAX: [phone]
COLORADO
D I V I S I O N OF
RECLAMATION
MINING
SAFETY
Bill Ritter, Jr.
INTEROFFICE MEMORANDUM Governor
Harris D. Sherman
Executive Director
Date: 29 May 2009 Ronald W. Cattany
Division Director
Natural Resource Trustee
To: Joe Dudash
From: Marcia L. Talviti?,P.E.
Subject: Bowie No. 2 Mine (Permit No. C-1996-083)
TR-61 - Coal Refuse Pile Slope Inclination
Adequacy Comments (Geotechnical)
The application for TR-61 was prepared to update the permit application package to
reflect a steepened slope configuration for Coal Mine Waste Disposal Area #2
(CMWDA2) that was previously approved under TR-56. With TR-56, the operator
successfully demonstrated [in a report prepared by Buckhom Geotech, Inc. (BGI)] that
slopes as steep as 3H:1 V for the upper portions of CMWDA2 will provide a Factor of
Safety of 1.50 when proper methods of construction are used and site conditions are
periodically monitored.
In its review for TR-56, the Division listed several items that the upcoming technical
revision application (TR-61) would be expected to address. Those items are each
repeated below ("OC", for "Original Comment"), followed by an evaluation of the
current TR-61 application ("NC", for "New Comment").
Vibrating Wire Piezometers
OC: Five instruments were originally installed in four separate holes in 2005; two of
the piezometers (in two holes) later ceased to function. Pore pressure data from the
remaining three piezometers were utilized to develop assumptions for use in the
stability evaluation. In Section 6.0 (Page 14 of 15), BGI recommends on-going
monitoring of piezometers as construction of CMWDA2 progresses.
Please describe the proposed on-going piezometric monitoring plan, including the
locations of any new piezometers to be placed, any anticipated modification of
existing piezometers, and the proposed monitoring frequency.
Office of Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines