2022-01-27_PERMIT FILE - C1981019 ‎(7)‎

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 1/27/2022
• Doc Name: Addendum Collom and South Taylor Highwall Mining Geotechnical Design
• Section_Exhibit Name: Volume 20 Exhibit 27 Item 7
• Media Type: D
• Archive: No

Mr. Lee Sampson
December 7, 2021
Page 8

Agapito Associates, Inc.

Figure 3a. Web Pillar Design Chart—Collom B2/B3 Seam
Design
Depth of Cover, ft 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9
110 49 53 58 62 66 70 73 77 81 84 87 91 94
130 55 59 64 68 73 77 81 85 89 93 97 101 104
150 62 66 70 74 79 84 89 93 98 102 106 110 114
170 68 73 78 82 86 91 96 101 106 110 115 120 124
190 74 80 85 90 95 99 104 108 113 119 124 129 134
210 80 86 92 98 103 108 113 118 122 127 132 137 143
230 86 93 99 106 112 117 123 128 133 138 143 148 152
250 91 99 106 113 120 126 132 138 144 149 155 160 165
270 97 105 113 121 128 135 142 148 154 161 166 172 178
290 103 112 120 128 136 144 151 158 165 172 178 185 191
310 108 118 127 136 144 152 160 168 175 183 190 197 204
330 113 124 134 143 152 161 170 178 186 194 202 209 217
350 119 130 140 150 160 170 179 188 196 205 213 221 229
Coal strength, psi 495 Mining width, ft 11.50 No. web pillars 19
Pillar widths in italics have width-to-height ratios of 0.8
Mining Height, ft
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
48
60
72
84
96
108
120
132
144
156
168
180
192
204
216
228
240
110 130 150 170 190 210 230 250 270 290 310 330 350 REQUIRED WEB PILLAR WIDTH, ftREQUIRED WEB PILLAR WIDTH, in DEPTH OF COVER, ft
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
Mining
Height,
ft