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<br />factors such as compaction and strength of the roof rock, tectonic <br />stresses and configuration of the surface. <br />Western Fuels has selected 300 feet as the minimum overburden thickness <br />to ensure a dependable, controllable longwall system. <br />3. The Williams Fork formation has several coal seams of various <br />thiclmesses. The D Seam, which will be mined during the first permit <br />term, la overlaid by the E coal seam. The interburden thickness between <br />these tyro seams averages 12 feet, however, In certain areas this <br />interval is lass than 4 feet thick. <br />Thin beds oP roof rock overlaid by weak zones of coal can create a <br />serious roof control problem. Although this unfavorable roof condition <br />will be controllable on the longwall face it may be impossible to <br />contain in the gate roads. This problem is created by the pressure wave <br />which precedes the longwall face. This pressure can cause separation of <br />the strata and collapse of the rock interval unless the interburden is <br />of adequate thickness or unless it can be bolted to an overlying compact <br />stratum. <br />Western Fuels has decided that in order to ensure an adequate inherenE <br />bearing capacity the interval between the D and overlying E Seam should <br />not be less than 7 feet in areas planned for loagwall mining. <br />U Mining Method Decision <br />The above criteria governed the selection of the mining system for the permit <br />term 1981-1989 as shown on Map Ne. 119. The areas close to the outcrop on the <br />south of the mixing area were unsuitable for longirall mining due to the low <br />overburden height. Areas on the east and north of the permit area designated by <br />RPI, APII and RPIII were excluded from longwall mining because the rock interval <br />between the D and E Seams is less than 7 Peet thick. In addition, parts of Room <br />and Pillar Areas II and III have a total seam thickmess less than five feet. <br />Western Fuels has designed a mining plan Which will give the highest resource <br />recovery in the safest and most economical manner. <br />MINE FACILITIES <br />DETAILED DESIGN AND ROOTING INFORMATION SHOULD HE PROVIDED FOR THAT PORTION OF <br />THE OVERLAND COAL CONVERYOR TO BE LOCATED WITHIN THE PERMIT AREA. <br />Details on the overland conveyor from the "D" Portal Area to the railroad <br />loadout area are shown on Maps 103-118. <br />C 1 <br />J <br />10.80 13 <br />