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Mr. Lee Sampson <br /> April 23, 2021 <br /> Page 5 <br /> Design Mining Height, ft <br /> Depth of Cover, ft 6 7.25 8.5 9.75 11 12.25 13.5 14.75 16 1 17.251 18.5 119.75 21 <br /> 100 72 87 102 117 132 147 162 177 1921 2071 2221 237 252 <br /> 140 72 87 102 117 132 147 162 177 1921 207 222 237 252 <br /> 180 72 87 102 117 132 147 162 177 1921 207 222 237 252 <br /> 220 78 87 102 117 132 147 162 177 1921 207 222 237 252 <br /> 260 92 99 106 117 132 147 162 177 192 207 222 237 252 <br /> 300 105 116 122 130 138 147 162 177 192 207 222 237 252 <br /> 340 115 128 140 151 158 166 174 183 192 207 222 237 252 <br /> 380 127 141 154 167 180 192 201 209 216 225 234 243 252 <br /> 420 139 154 169 183 198 212 226 240 252 261 270 278 287 <br /> 460 151 168 184 199 216 232 248 264 279 294 309 324 334 <br /> 500 162 181 200 217 234 252 270 288 305 323 340 357 374 <br /> 540 174 195 215 234 253 272 292 312 332 351 371 390 409 <br /> 580 185 208 230 251 272 292 314 336 358 380 402 423 445 <br /> Coal strength, psi 900 Mining width, ft 11.50 No. web pillars 19 <br /> Pillar widths in italics have width-to-height ratios of 1.0 <br /> 456 38 <br /> 432 36 <br /> 408 34 <br /> Mining <br /> 384 32 Height, <br /> ft <br /> 360 30 <br /> t 6 <br /> 336 + 28 <br /> - 7.25 <br /> p 312 26 0 <br /> + 8.5 <br /> Q 288 24 Q +9.75 <br /> J + J <br /> 0. <br /> J <br /> m 264 fi 22 a — 11 <br /> W CIO <br /> LU 20 12.25 <br /> 8 13.5 <br /> 216 — 18 W41 _ <br /> D —F 14.75 <br /> 192 - + 16 0 <br /> + 16 <br /> 168 7111171111711117111171 <br /> 14 t 17.25 <br /> 144 12 —18.5 <br /> 120 Id10 19.75 <br /> 96 - 8 21 <br /> 72 6 <br /> 100 140 180 220 260 300 340 380 420 460 500 540 580 <br /> DEPTH OF COVER,ft <br /> Figure 2a. Web Pillar Design Chart—South Taylor G78 Seam <br /> Agapito Associates, Inc. <br />