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• This pillar loading is a worst case analysis, and will be lower in reality due to the formation of a pressure arch above the entries, therefore, a safety factor greater than two is considered to be very acceptable. The mining induced loads onto the main entry pillars due to excavation of the main entries will result in a slight compression of these pillars which will result in negligible subsidence at the surface. Therefore, even with the worst case situation at the greatest depth for the main entry stability, there is no likelihood of damage to surface structures and renewable resource lands as a result of subsidence. PANEL SUBSIDENCE Longwall production panels in the five year mine plan will have gateways driven on advance with production on retreat. Rooms will be advanced in production sections and pillars will be extracted on retreat. During retreat in both mining methods, the roof will be allowed to cave into the gob; the extent of this cave is dependent upon the extraction height which is expected to be a maximum of 10 ft. (Room and Pillar mining never produces full extraction, thus the expected maximum for Room and Pillar will be lower than the longwall panel predictions that have been presented as maximum predicted subsidence). The limit of the upper caving zone is the point when the strata beds do not fracture, but remain intact and their flexure allows bridging between the forward abutment and the consolidated gob. The upper caving limits are not expected to extend beyond 100 ft. above the seam (ten times the extraction height). At the planned mining depth of up to 1,100 ft., there is no likelihood that any cave will extend to surface. Above the upper caving limits there will be a region where bed separa- tion, but no vertical fracturing, wil] occur. The worst case extension of this bed separation is expected to be 300 ft. above the seam (30 times extracted height). Ex. 7-4