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 46
Design Depth
of Cover (ft)
Mining Height (ft)
4 T
4.5
5
5.5
6
6.5
7
8
9
10
11
12
13
100
5.5
5.8
6.1
6.5
6.8
7.1
7.4
7.9
8.4
8.9
9.4
9.9
10.4
130
7.6
7.9
8.3
8.6
8.9
9.2
9.5
10.3
10.9
11.6
12.2
12.8
13.4
160
9.8
10.3
10.8
11.2
11.6
12.0
12.4
13.1
13.8
14.3
15.0
15.8
16.5
190
12.0
12.6
13.3
13.8
14.4
14.9
15.4
16.3
17.2
18.0
18.7
19.4
20.1
220
14.2
15.0
15.81
16.5
17.1
17.8
18.4
19.5
20.6
21.6
22.5
23.4
24.3
250
16.5
17.4
18.3
19.1
19.9
20.7
21.4
22.8
24.1
25.3
26.4
27.5
28.5
280
18.7
19.8
20.8
21.8
22.7
23.6
24.4
26.1
27.6
29.0
30.3
31.6
32.8
310
20.9
22.2
23.3
24.5
25.5
26.5
27.5
29.3
31.0
32.7
34.2
35.7
37.1
340
23.2
24.6
25.9
27.1
28.3
29.4
30.5
32.6
34.6
36.4
38.1
39.8
41.4
370
25.4
27.0
28.4
29.8
31.1
32.4
33.6
35.9
38.1
40.1
42.0
43.9
45.7
400
27.7
29.4
31.0
32.5
33.9
35.3
36.6
39.2
41.6
43.8
46.0
48.0
50.0
430
29.9
31.8
33.5
35.2
36.7
38.2
39.7
42.5
45.1
47.6
49.9
52.2
54.3
460
32.21
34.2
36.01
37.8
39.5
41.2
42.8
45.8
48.6
51.3
53.91
56.3
58.7
Coal Strength (psi) 900 Mining Width (ft) 11.50
'Pillar widths in italics have width -to- height ratios of 0.8
60
50
w
x
0 40
3
Q
J
_J
a 30
g
�a
20
5
10
0
50 100 150 200 250 300 350 400 450 500
DEPTH OF COVER (ft)
No. Web Pillars 19
Figure 31b. Barrier Pillar Design Chart -West Pit, F and E Seams
Agapito Associates, Inc.
Mining
Height
(ft)
�- 4
4.5
-x- 5
-5.5
6
6.5
7
-- 8
9
-� 10
11
12
13