2012-08-03_PERMIT FILE - C1981012 ‎(4)‎

• Permit No: C1981012
• IBM Index Class Name: Permit File
• Doc Date: 8/3/2012
• Doc Name: Design Recommendations for the Proposed West Portal Development Waste Rock Disposal Area ‎(DWDA)‎
• Section_Exhibit Name: Exhibit 43
• Media Type: D
• Archive: No

April 16, 2012 Page 9
maximum dry density as determined by the standard proctor (ASTM D698) and to within f2%
of the optimum moisture content.
Table 4. Summary of Laboratory Direct Shear and Unconfined Compressive Strength
Test Results
Sample
Sample
Peak Strength
Residual Strength
ID
Depth
Friction, V
Cohesion, c
Friction, cp
Cohesion, c UCS
(ft bgs)
(degrees)
(psf)
(degrees)
(psf) (psi)
BH -38
5.5
12
680
-
- -
BH -38
15.5
21
0
20
0 -
BH -40
6.25
9
1,675
11
1,155 -
BH -40
11.25
-
-
-
- 4,750
BH -41
6
22
215
19
255 -
DWR
Stockpile
17
510
17
445 -
5.0 COMPUTER -AIDED MODELING AND ANALYSIS
As presently envisioned, the proposed DWDA near the West Portal has a maximum base
(ground surface) width and length of approximately 400 ft by 720 ft, respectively. The toe of the
embankment is at an elevation 7,620 ft and the crest elevation is at an elevation of 7,710 ft.
Since the ground surface slopes moderately to the north, the maximum section or thickness of
development waste rock would be approximately 90 ft. Side slopes of 3(horizontal
[H]):1(vertical [V]), 2.5(H):1(V) and 2(H):1(V) were considered and these geometries were
modeled using Geo- Slope's Slope /W software to evaluate various DWDA slope configurations.
Waste rock and foundation material properties were established by evaluating the
laboratory data determined from testing samples obtained from the geotechnical investigation.
Material properties used in our analysis are summarized in Table 5. The values of properties
presented in Table 5 are considered to be realistic, yet conservative, estimates of the materials
present at the site.
Table 5. Summary of Material Properties Used for Slope Stability Analysis
Results of the computer modeling analysis are summarized in Table 6. Analyses in
support of the stability factors summarized in Table 6 are presented in Figures 2 through 7.
4 Geo -Slope International (2009), GeoStudio 2007, Version 7.14, April 20.
Agapito Associates, Inc.
Shear Strength
Material
Material Description
Density, y
Friction, 9
Cohesion, c
(lbs /ft3)
(degrees)
(lbs /ft')
Waste rock
Silty, clayey GRAVEL (GW)
103.0
17
400
Clayey alluvium
Sandy CLAY (CL)
132.0
10
1,600
Sandy alluvium
Clayey SAND (SC)
105.0
22
200
Bedrock
Medium -grain sandstone
140.0
34
500
Results of the computer modeling analysis are summarized in Table 6. Analyses in
support of the stability factors summarized in Table 6 are presented in Figures 2 through 7.
4 Geo -Slope International (2009), GeoStudio 2007, Version 7.14, April 20.
Agapito Associates, Inc.