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 11

Agapito Associates, Inc.

Figure 4a. Web Pillar Design Chart—Collom C3/C5 Seam
Design
Depth of Cover, ft 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11
130 51 54 58 63 68 72 77 82 87 92 96 101 106
160 58 61 64 67 70 73 77 82 87 92 96 101 106
190 64 68 71 75 78 81 85 88 91 94 97 101 106
220 70 74 78 82 85 89 93 96 100 103 107 110 113
250 75 80 84 88 92 97 101 104 108 112 116 120 123
280 81 85 90 95 99 104 108 112 116 121 125 129 133
310 86 91 96 101 106 111 115 120 124 129 133 138 142
340 94 98 102 107 112 117 122 127 132 137 142 146 151
370 101 105 110 115 119 124 129 135 140 145 150 155 160
400 108 113 118 123 128 132 137 142 147 153 158 163 169
430 114 120 126 131 137 142 147 152 156 161 166 172 177
460 121 128 134 140 145 151 156 162 167 172 177 182 187
490 128 135 142 148 154 160 166 172 178 183 189 194 199
Coal strength, psi 900 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
48
60
72
84
96
108
120
132
144
156
168
180
192
204
216
130 160 190 220 250 280 310 340 370 400 430 460 490 REQUIRED WEB PILLAR WIDTH, ftREQUIRED WEB PILLAR WIDTH, in DEPTH OF COVER, ft
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
10.5
11
Mining
Height,
ft