PERMFILE134752

• Permit No: M2000087
• IBM Index Class Name: Permit File
• Doc Date: 9/19/2000
• Doc Name: MEMO SECOND STABILITY ANALYSIS FOR MILLIKEN PIT APPLICATION M-2000-087
• From: DMG
• To: TOM SCHREINER
• Media Type: D
• Archive: No

~ III IIIIIIIIIIIII III ~
STATE OF
COLORADO
DIVISION OF MINERALS AND GEOLOGY
Depanmenf of Natural Resources
1313 Sherman SL, Roam 215
D I V I S I O N O F
Denver, Colorado 80203
Phone: [phone] MINERAL S
FAX: [phone] &
GEOLOGY
RECLAMATION
MINING•SAFETY
MEMO Bill Ovens
Grnernor
DATE: September 19, 2000 ereti F. walcner
TO: Tom Schreiner E+eculrve Direcmr
Cr. Carl B. Mount

FROM: Christina Kamnikar~ Mi~nael B. wog
Division DueUOr
RE: Second Stability Analysis for Milliken Pit application, #M-2000-087
Rocky Mountain Consultants adequately responded to my concerns regarding missing information in the
stability analysis. After reviewing their newest submittal, I was able to determine [hat a safety factor of 1.48
could be obtained under the conditions outlined in their geotechnical modeling example. However, I believe
[he following limitations should still be put on their setback request.
1) The slurry wall must remain 3.8" thick, since this is the thickness modeled for in the analysis. Any other
changes in the dimensions should necessitate a new analysis of the slope stability.
2) The 20' clearance on the non-mined side of the slurry wall should be committed to around the perimeter,
to allow for adequate constmction area consistent with this project's specifications.
3) While the preliminary analysis indicates that mining 65' deep, at an angle of 2H:1 V, with a 20' setback
from the lip of the excavation before the placement of the slurry wall, does guarantee a minimum factor of
safety of I.S, DMG would like to recommend that a setback from the toe of the embankment be
committed to, rather than a setback from the edge of the excavation. This allows the Operator to mine at
any angle which is convenient for the operation, instead of forcing the excavation to comply with [he strict
grade requirement above. If this course of action is taken, DMG would require a minimum setback from
the toe of the excavation of 1 17 feet before the slurry wall is constructed.
If you have any further questions, please feel free to contact me at [phone].
C.L. Kamnikar
Cc: Carl B. Mount, DMG
Allen Sorenson, DMG