2021-05-27_PERMIT FILE - C1981019 ‎(10)‎

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 5/27/2021
• Doc Name: Geotechnical Stability Report For Highwall Mining At the Colowyo Coal Mine
• Section_Exhibit Name: Exhibit 23, Item 1
• Media Type: D
• Archive: No

March 21, 2014
Page 52
Design Depth
Mining Height
(ft)
of Cover (ft)
4
4.25
4.5
4.75
5
5.25
5.5
5.75
6
6.25
6.5
6.75
7
100
5.5
5.7
5.9
6.1
6.2
6.4
6.6
6.7
6.9
7.0
7.2
7.3
7.5
120
7.0
7.2
7.3
7.5
7.6
7.8
7.9
8.1
8.3
8.4
8.6
8.8
9.0
140
8.5
8.7
8.9
9.1
9.3
9.5
9.7
9.9
10.0
10.2
10.4
10.5
10.7
160
10.0
10.2
10.5
10.8
11.0
11.2
11.5
11.7
11.9
12.1
12.3
12.5
12.7
180
11.5
11.8
12.1
12.4
12.7
13.0
13.2
13.5
13.8
14.0
14.2
14.5
14.7
200
13.0
13.4
13.7
14.1
14.4
14.7
15.0
15.3
15.6
15.9
16.2
16.5
16.8
220
14.5
14.9
15.3
15.7
16.1
16.5
16.8
17.2
17.5
17.8
18.2
18.5
18.8
240
16.0
16.5
16.9
17.4
17.8
18.2
18.6
19.0
19.4
19.8
20.1
20.5
20.8
260
17.5
18.1
18.6
19.0
19.5
20.0
20.4
20.9
21.3
21.7
22.1
22.5
22.9
280
19.1
19.6
20.2
20.7
21.2
21.7
22.2
22.7
23.2
23.6
24.1
24.5
25.0
300
20.6
21.2
21.8
22.4
23.0
23.5
24.0
24.6
25.1
25.6
26.1
26.6
27.0
320
22.1
22.8
23.4
24.1
24.7
25.3
25.9
26.4
27.0
27.5
28.1
28.6
29.1
340
23.6
24.4
25.1
25.7
26.4
27.0
27.7
28.3
28.9
29.5
30.0
30.6
31.2
Coal Strength (psi) 871 Mining Width (ft) 11.50
'Pillar widths in italics have width -to- height ratios of 0.8
35
30
0 25
3
Q
J
J_
CL 20
n
r
!n
f
5
10
F�
50 100 150 200 250 300 350
DEPTH OF COVER (ft)
No. Web Pillars 19
Figure 33b. Barrier Pillar Design Chart -West Pit, C Seam
Agapito Associates, Inc.
Mining
Height
(ft)
-+ -4
4.25
mac- 4.5
-4.75
5
5.25
5.5
-f - 5.75
6
�- 6.25
6.5
6.75
7