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 49
Design Depth
of Cover (ft)
Mining Height
(ft)
4
4.25
4.5
4.75
5
5.25
5.5
5.75
6
1 6.25
6.5
6.75
7
100
6.8
6.9
7.1
7.3
7.4
7.5
7.7
7.9
8.1
8.2
8.4
8.6
8.8
125
8.9
9.2
9.4
9.6
9.8
10.1
10.3
10.5
10.6
10.8
11.0
11.2
11.3
150
11.2
11.5
11.8
12.0
12.3
12.6
12.9
13.1
13.4
13.6
13.9
14.1
14.3
175
13.4
13.7
14.1
14.5
14.8
15.2
15.5
15.8
16.1
16.4
16.7
17.0
17.3
200
15.6
16.0
16.5
16.9
17.3
17.7
18.1
18.5
18.9
19.3
19.6
20.0
20.3
225
17.8
18.3
18.9
19.4
19.9
20.3
20.8
21.2
21.7
22.1
22.5
23.0
23.4
250
20.0
20.7
21.2
21.8
22.4
22.9
23.5
24.0
24.5
25.0
25.5
25.9
26.4
275
22.3
23.0
23.6
24.3
24.9
25.5
26.1
26.7
27.3
27.8
28.4
28.9
29.5
300
24.5
25.3
26.0
26.7
27.4
28.1
28.8
29.4
30.1
30.7
31.3
31.9
32.5
325
26.8
27.6
28.4
29.2
30.0
30.7
31.4
32.2
32.9
33.6
34.2
34.9
35.6
350
29.0
29.9
30.8
31.7
32.5
33.3
34.1
34.9
35.7
36.4
37.2
37.9
38.6
375
31.2
32.2
33.2
34.1
35.0
35.9
36.8
37.7
38.5
39.3
40.1
40.9
41.7
400
33.5
34.6
35.6
36.6
37.6
38.5
39.5
40.4
41.31
42.2
43.1
43.9
44.7
Coal Strength (psi) 651 Mining Width (ft) 11.bU
'Pillar widths in italics have width -to- height ratios of 0.8
45
40
35
0
a: 30
J
J
a
25
a
8 20
5
W
10
VQ
1�
5
50 100 150 200 250 300 350 400 450
DEPTH OF COVER (ft)
No. Web Pillars 1y
Figure 32b. Barrier Pillar Design Chart -West Pit, D2 Seam
Agapito Associates, Inc.
Mining
Height
(ft)
4
4.25
mac- 4.5
-4.75
5
5.25
5.5
t� 5.75
6
- 0 6.25
6.5
6.75
7