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 45
Design Depth
Mining Height (ft)
of Cover (ft)
4
4.5
5
5.5
6
6.5
7
8
9
10
11
1 12
13
100
39
44
48
53
58
63
68
77
87
96
106
116
125
130
44
47
50
53
58
63
68
77
87
96
106
116
125
160
49
53
56
59
62
65
68
77
87
96
106
116
125
190
55
58
62
66
69
73
76
82
88
96
106
116
125
220
59
64
68
72
75
79
83
90
97
103
110
116
125
250
64
69
73
77
82
86
90
97
105
112
119
126
133
280
69
73
78j
83
87
92
96
105
113
121
129
136
144
310
75
79
83
88
93
98
103
112
120
129
137
146
154
340
81
85
90
94
99
104
109
119
128
137
146
155
164
370
86
92
96
101
105
110
115
125
135
145
155
164
174
400
92
98
103
108
113
118
122
132
142
153
163
173
183
430
98
104
110
115
121
126
131
140
150
161
171
182
193
460
1031
1101
128
134
139
149
1591
169
1801
191
202
Goal Strength (psi) 9UU Mining Width (ft) 11.5U
`Pillar widths in italics have width -to- height ratios of 0.8
240
180
L
U
C
x
o_
Q
120
a
e
60
20
15
0
Q
10 a
e
5
0 0
50 100 150 200 250 300 350 400 450 500
DEPTH OF COVER (ft)
No. Web Pillars 19
Figure 31a. Web Pillar Design Chart —West Pit, F and E Seams
Agapito Associates, Inc.
Mining
Height
(ft)
-+ 4
4.5
5
5.5
6
6.5
7
8
9
—+— 10
-� 11
12
13
I —
' —
-- �-
I
20
15
0
Q
10 a
e
5
0 0
50 100 150 200 250 300 350 400 450 500
DEPTH OF COVER (ft)
No. Web Pillars 19
Figure 31a. Web Pillar Design Chart —West Pit, F and E Seams
Agapito Associates, Inc.
Mining
Height
(ft)
-+ 4
4.5
5
5.5
6
6.5
7
8
9
—+— 10
-� 11
12
13