2013-01-10_REVISION - M1982131

• Permit No: M1982131
• IBM Index Class Name: REVISION
• Doc Date: 1/10/2013
• Doc Name: REVIEW OF SLOPE STABILITY ANALYSIS
• From: DRMS
• To: OPERATOR
• Type & Sequence: TR1
• Email Name: PSH
• Media Type: D
• Archive: No

DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE:
January 10, 2013
TO: Carrie Herbolsheim r, PE
Applegate Grouygnc.
FROM: Peter Hays
STATE OF COLORADO
RE: Review of Slope Stability Analysis, Bucklen Equipment Company Pit, Bucklen Pit,
File No. M- 1982 -131, Technical Revision No. 1
COLORADO
D I V I S I O N O F
RECLAMATION
MINING
— &—
SAE ETY
John W. Hickenlooper
Governor
Mike King
Executive Director
Loretta Pineda
Director
The Division of Reclamation, Mining and Safety (DRMS) staff has reviewed the stability analysis dated
November 29, 2012, included with the Bucklen Pit adequacy response letter dated December 18, 2012 for
technical revision no. 1.
The stability analysis was conducted by Applegate Group, Inc. (Applegate) on two different conditions,
one for the mining condition, during which slopes were excavated at a 1H:1V grade and one for the
reclamation condition, during which the embankment backfill will be placed at no steeper than a 3H:1V
grade. The calculations were performed using the XSTABL slope stability software. The report states the
soil parameters used for the analysis were based on values used in the past for slope stability calculations
and guidelines in the USBR publication "Design of Small Dams ".
The soil parameters used by Applegate in the stability analysis differ considerably from the DRMS
requirements for temporary pit slopes and the accepted geotechnical standards. A copy of the DRMS
requirements and standard soil properties for stability analyses when no laboratory strength tests were
performed on the on -site soils is included for reference.
Using Clover Technology's Galena v5.02 slope stability software, the DRMS conducted further analysis of
the cross sections for the Bucklen Pit. The following list describes the information and methodology used
by the Division to analyze slope stability for the proposed slope configurations:
1. Mine highwalls were modeled at 1H:1V slopes and reclaimed slopes were modeled at 3H:1V.
2. Residual soil strength parameters were used for the upper 2.5 feet of weathered bedrock in the
slope analysis.
3. Factor of Safety must be greater than 1.0.
4. Groundwater level on the mined profile was input to portray site dewatering.
5. Laboratory strength tests were not performed on soils from the site. The soil strength parameters
used were based on typical values for the anticipated soils and Applegate provided soil values.
6. The scenarios were modeled with general sections developed by Applegate for the stability
analysis.
Office of Office of
Mined Land Reclamation
Denver • Grand Junction • Durango Active and Inactive Mines