PERMFILE115389

• Permit No: M2001046
• IBM Index Class Name: Permit File
• Doc Date: 6/3/2002
• Doc Name: Geotechnical Review
• From: Al Amundson
• To: Tony Waldron
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman SL, Room 215
Denver, Colorado 80203 DIVISION O F
Phone: [phone] /bl 1 l~l l: RA 1. $
FAX: [phone] &
Memo Geol.ocv
R E C L A M A T I O N
To: Mr. Tony W aldron
~
0 MININ G•SAi ETA
From: AI Amundson, P.E.
/i(
\
" \
June 3, 2002 col °~a°~
Subject: Nix Pit M-2001-046 Geotechnical Review Gres E. walcner
Executive Director
I have completed a limited review of the assumptions and slope stability analysis (SSA) perfor~ p;r`e nor
by Ms Danielle Volpe, P.E. of Banks and Gesso on the subject pit and find the SSA to be adequate
for the assumptions and conditions specified. The conditions being accepted by the Division of
Minerals and Geology (DMG) are as specified in 3.1.5 (7) of the rules: 3:1 slopes from 5 feet above
to 10 feet below water level, and 2:1 slopes from 10 feet below water level to the bottom of the
excavation. The excavation is proposed to extend to no closer than 25 feet from the county roads
and the power lines. These slopes are to be mined, not backfilled. If backfilling becomes necessary,
a plan for de-watering and placement of compacted fill shall be presented to DMG, including a
stability analysis for de-watering of the pit.
Method:
Values listed in the Banks and Gesso SSA were entered into the Galena Slope Stability program,
including an appropriate seisimic acceleration (K=0.025). The Galena program yielded results
approximating those presented by Banks and Gesso, corrected for the seismic acceleration.
Limitations:
DMG Inspectors should verify that slopes aze being mined appropriately, especially as the
excavation approaches the 25 foot buffer to man-made structures, and inspect for tension cracks or
slumping of the bank. In the event cracking or slumping occurs with mining, the DMG must be
notified and the stability of the system re-evaluated.
If cracking or slumping occurs within the 25 foot buffer, DMG must be notified, mining is to cease
or move to an azea outside the statutory 200 foot setback and an investigation conducted. Slope
stability must be demonstrated prior to mining continuing in the area between 25 and 200 feet from
the man-made structures.
The operator is cautioned that all disturbance, topsoil stripping and equipment operation must occur
within the mine permit boundazies.