2012-08-31_PERMIT FILE - C1981012 ‎(2)‎

• Permit No: C1981012
• IBM Index Class Name: Permit File
• Doc Date: 8/31/2012
• Doc Name: Development Waste Disposal Area ‎(DWDA)‎ #2 Slope Stability Evaluations
• Section_Exhibit Name: Exhibit 37‎(1)‎ Development Waste Disposal Area ‎(DWDA)‎
• Media Type: D
• Archive: No

Mr. Daniel Hernandez
May 25, 2012
Page 3
The computer program Slope /W (GeoStudio 2007) was utilized to evaluate the DWDA
slope configuration. Material properties assigned to the waste rock and underlying alluvium
were consistent with properties used in the previous stability analysis (AAI 201 0)2 with the
exception of the internal friction angle assigned to the waste rock. Previously reported waste
rock internal friction of 37 degrees ( °) was considered to be relatively high and therefore, for
conservatism, this value was reduced to 30 °. Table 1 summarizes the material properties used in
the analysis.
Table 1. Summary of Material Properties Used for Slope Stability Analysis
Material Unit Weight, r Internal Friction, y Cohesion, c
(Ibs /ft3) (degrees) (Ibs /ft)
Waste rock 110 30 460
Alluvium (subgrade) 90 38 760
Results of the computer modeling analysis area are summarized in Table 2. Analyses in
support of the stability factors summarized in Table 2 are presented in Figures 2 through 5.
Table 2. Stability Factors for Various DWDA Slope Conditions
Recommendations
Based on the material properties used and the subsequent computer -aided modeling and
analysis, AAI recommends that DWDA #2 be constructed to the criteria in Table 3.
Several factors including foundation preparation, surface and subsurface water drainage,
and coal waste rock placement, affect the stability and performance of the waste pile. The
following recommendations are provided to fulfill assumptions made in the stability analysis and
are necessary to ensure an adequate safety margin is maintained: II
I Geo -Slope International (2009), GeoStudio 2007, Version 7.1.4, April 20. II
2 Agapito Associates, Inc. (2010), "Design Recommendations for the Development Waste Disposal Area, New Elk
Mine, Weston, Colorado," report prepared for Cline Mining Corporation, September, 13 pp.
Agapito Associates, Inc.
TR 66 Page E 37 -4 Revised 5/25/2012
Side Slope
Groundwater (Phreatic)
Stability
Figure
Configuration
Location
Factor
2
2.0(H): 1.0(V)
At existing ground surface
2.3
3
2.0(H): 1.0(V)
5 ft above ground surface
2.3
4
2.0(H):1.0(V)
10 ft above ground surface
2.1
5
2.0(H):1.0(V)
20 ft above ground surface
1.9
Recommendations
Based on the material properties used and the subsequent computer -aided modeling and
analysis, AAI recommends that DWDA #2 be constructed to the criteria in Table 3.
Several factors including foundation preparation, surface and subsurface water drainage,
and coal waste rock placement, affect the stability and performance of the waste pile. The
following recommendations are provided to fulfill assumptions made in the stability analysis and
are necessary to ensure an adequate safety margin is maintained: II
I Geo -Slope International (2009), GeoStudio 2007, Version 7.1.4, April 20. II
2 Agapito Associates, Inc. (2010), "Design Recommendations for the Development Waste Disposal Area, New Elk
Mine, Weston, Colorado," report prepared for Cline Mining Corporation, September, 13 pp.
Agapito Associates, Inc.
TR 66 Page E 37 -4 Revised 5/25/2012