PERMFILE64489

• Permit No: M2003091
• IBM Index Class Name: Permit File
• Doc Date: 9/17/2004
• Doc Name: Adequacy Review #3
• From: DMG
• To: LaFarge West Inc
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY /
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
September 17, 2004
Mr. Eric Reckentine
Lafazge West, Inc.
1400 West 64`~ Ave.
Denver, CO 80221
RE: Lafazge West, Inc., Application No. M-2003-091
Duckworth Pit; Adequacy Review #3
Deaz Mr. Reckentine,
COLORADO
D I V I S I O N O F
MINERALS
GEOLOGY
RECLAMATION•N IN ING
SAFETY•SCIENCE
Bill Owens
Governor
Russell George
Executive Director
Ronald W. Cottony
Division Director
Natural Resource Trustee
The Division received Lafazge's adequacy response on September 1, 2004 for the Duckworth Pit
New 112 Application, File Number M-2003-091. The Division of Minerals and Geology
(Division) is required to make an approval or denial recommendation no later than October 27,
2004, therefore, your response to the following adequacy review concerns should be submitted to
the Division as soon as possible.
The Division previously asked Lafarge to demonstrate topsoil piles stored on site would be stable
in their current configuration if an adequate buffer distance was not established. Lafazge
responded by changing the mining slope from O.Sh:ly to 1.Sh:ly and stating that an angle of
repose equal or less than 1.5:1 achieves a safety greater than 1. However, Lafarge did not
provide a slope stability analysis to demonstrate that the angle of repose would achieve a static
safety factor greater than 1. The Division previously provided Lafarge with the following
options regazding placement of the topsoil piles:
• Demonstrate that topsoil piles will be stable under the proposed mining conditions using
a stability slope analysis (according to the map, the topsoil pile is on the top edge of the
mining limits),
• Maintain a set back distance at 2 times the depth of the pit (in this case a 20' deep pit
would need a 40' setback distance) and revise the maps to reflect this buffer,
• Revise the mining and reclamation plan to include sloping, benching or terracing and
including a slope stability analysis, or
• Relocate the topsoil pile to a more stable location, and revise the maps accordingly.
Lafarge has not provided a mining offset distance from the toe of the topsoil pile to the edge of
the pit, nor has Lafazge demonstrated that the pile will be stable at the edge of the 1.Sh:ly pit.
Please address this issue prior to fmal approval of the Duckworth 112 Application. In addition,
please explain how the highwalls will be reduced and reclaimed in areas where topsoil is stored.
Office of
Mined Land Reclamation
Office of
Active and Inactive Mines
Colorado
Geological Survey