Laserfiche WebLink
mining proved successful, it did not provide the needed productivity gains and quality <br />• needed to make this mine profitable. All mining activities in the C-Seam have ceased, <br />retreat mining has been completed and all mining machinery recovered. There are no <br />plans to reinitiate mining at the North or South Portal. <br />Subsidence and Ground Control <br />Figure 5-3 shows the overburden, creek channels, subsidence protection zones <br />and the extent of mining relative to the C seam. The subsidence protection zones are <br />based upon a 12° angle of draw as required in TR-06. For all depths up to 400 feet of <br />overburden, a protection zone 200 feet wide will be adequate. The Jerry Creek <br />drainage reaches a maximum of 400 feet at the Federal Lease boundary. The Coal <br />Creek drainage generally is less than 300 feet of overburden with most of the area <br />about 200 feet. The outline of the 200 foot subsidence protection zone is shown on <br />Figure 5-3. No further extraction is planned for the C-Seam. <br />Table 12-4 indicates the factors of safety for various pillar dimensions while <br />mining in the C seam. The results are based upon strength analysis completed by the <br />University of West Virginia on two blocks of coal that were cut into five samples. The <br />results of the uniaxial compressive strength tests yield a range of 587 to 3,705 psi. <br />The average strength of the coal was of 1,820 psi. The pillar sizes were analyzed <br />using the computer program ARMPS, developed by the U. S. Bureau of Mines. Safety <br />factors varied from 4.6 for 70 feet by 80 feet with 400 feet of cover to 0.87 for 50 foot <br />by 50 foot with 1,000 feet of cover. The cover in the creek channels is less than 500 <br />feet in all areas to be undermined. Based upon the analysis of the coal and <br />dimensions of the pillars there should be no subsidence resulting from the C-Seam <br />mining. <br />Mining Hydrologv <br />• The hydrologic impact from mining the C seam should be negligible. Historically, <br />water has been pumped from the mine to Discharge Point 004. The source of the <br />Volume 3 Tab 12 12-5 5/00 <br />