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Development mining consists of 20 foot wide panel entries located at 70 foot <br /> centers leaving a 50 foot by 50 foot pillar and resulting in an extraction ratio <br /> of approximately 50 percent. Due to bad roof conditions above the "C" seam, Bear <br /> Coal Company was unable to accomplish any high extraction retreat mining within <br /> the "C' seam mine. Therefore, all the mining shown on the "C" seam mine plan <br /> (see Figure 2 ) remains at an extraction ratio of 50 percent. An extraction <br /> height on the order of six feet was typical throughout the "C" seam. <br /> Bear Coal Company also anticipates performing development mining within the <br /> "B" seam using the same 20 foot wide entries on 70 foot centers for a development <br /> mining extraction ratio of 50 percent. As has been mentioned previously, the <br /> inteiburden between the "B" and "C" seams is quite thin with only 35 to 40 feet <br /> of interburden anticipated. Bear Coal Company proposes to carefully columni.ze <br /> all entries and pillars in order to minimize the development of any dangerous <br /> roof stresses in the interburden above the "B" seam. Details of these mining <br /> methods and roof control, however, are beyond the scrape of this report. Bear <br /> Coal Company expects roof conditions above the "B" seam to be significantly <br /> improved aver those encountered above the "C" seam and would anticipate <br /> performing high extraction mining upon retreat. Bear anticipates an in panel <br /> extraction ratio after retreat on the order of 65 percent. Bear expects a <br /> typical extraction height within the "B" seam to be on the order of eight feet. <br /> Coal mining in the North Fork valley is associated with the clastic <br /> sediments of the Mesa Verde formation. 'These sediments were derived from distant <br /> western sources principally from the erosion of the Sevier Orogenic Belt in Utah. <br /> The sediments were transported eastward and were deposited on the western margin <br /> of the western interior Cretaceous seaway. Although there are no significant <br /> faults or folds mapped in the area, the coal seam does "roll" or exhibit some <br /> minor structure. Most of this type of structure is related to differential <br />