REP35820

• Permit No: C1980001
• IBM Index Class Name: Report
• Doc Date: 8/2/1995
• Doc Name: MOFFAT STABILITY CONCERNS EDNA MINE C-80-001
• From: DMG
• To: JIM PENDLETON
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

iii iiiiiiiiiiiiiiu
999
STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
Date: August 2, 1995
To: Jim Pendleton
From: Kent Gorha~ ~(-iU/
CC: David Berry
Larry Routten /
RE: Moffat Stability Concerns, Edna Mine, #C-80-001,
~"
~~~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Goverrgr
lames 5. Lachhead
Executive Director
Michael g. long
Division Director
As you may recall, I recently discussed with you my concerns about
the stability of the Moffat pit mining area at the Edna Mine.
Since that time I have had the opportunity to research some of the
permit documents, aerial photographs, monitoring data, and past
inspection reports. Based on this review, I believe a problem may
exist and or may develop in the future. i should add that the Edna
mine is closing operations and the opportunity to modify the Moffat
reclamation plan to address any stability concerns will be
approaching soon. in addition to your existing experience and
knowledge of the site, the following information may also be of
interest to you in evaluating the situation.
Please find enclosed photo A. This photo was taken in November of
1990, shortly after mining began in the Moffat area. As you can
see, the Moffat box cut spoil is being placed out of pit on a
previously mined surface. Due to past slides at the Edna mine, it
the record reveals that the Division expressed some valid concerns
that this mining activity could produce conditions which could lead
to instability and mass failure of this area. To alleviate or
address those concerns, the operator employed the services of a
consultant to conduct a study evaluating the stability of this area
given this mining scenario. This is included in the approved
permit, in Volume 7, as the Edna Mine Moffat Area Slope Stability
Analysis. As stated in the introduction, the purpose of this
report is to analyze the stability of the proposed out-of pit spoil
derived from the boxcut in the Moffat area. As shown in figure 2
of this report, the area studied focused only on the slope directly
~~s below the out-of-pit spoil, or the area upon which this spoil would
be placed. Figure 2 reveals that in this specific area, a
downgradient low wall or undisturbed barrier exists. Observation
of photo A focusing on the location of the pit seems to support
that fact.
Photo B was taken in July of 1993 and shows the pit advanced to the
north, moving into the main drainage area for the surrounding area.