2010-04-15_PERMIT FILE - C1994082 (5)

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• collecting and pumping surface and ground water that enter the pit. Sediment ponds are designed for controlling runoff from disturbed areas. All diversions and sediment ponds are designed in accordance with the regulations governing such structures and conform to currently accepted engineering practice. Power distribution at area surface mines such as Yoast, which utilizes high voltage electrical equipment, must be well planned for optimum accessibility. Power for stripping equipment is nomurlly fed from the highwall or undisturbed side of the operation for ease of access and to alleviate congestion in the pit and on the spoil side. Avery important task requiring utilization of the best available engineering techniques is the design of astable postmine land surface. Determination of such factors as spoil swell, stream gradients, postmine land use, spoil character, and foundation materials will affect the design of a land surface representing the approximate original contour. The currently accepted technique is to design a surface with slopes that do not exceed the average premining slope and with a general configuration that approximates the premining surface. Area suface mining is the most efficient method of recovery of a coal resource, especially in areas such as Yoast where the coal is of such a quality that it can be burned "raw", that is, without processing. ,The Wadge Caal seam and a small amount of the Wolf Creek coal seam will be mined to approximately 100 feet in depth (limitation of the stripping equipment) with a resource recovery rate approaching 91 percent. • Table 12-2 illustrates the anticipated acres mined and annual production of coal from October 1996 through the currently proposed life-of-operations. It is highly unlikely that the areas proposed to be mined will be redisturbed at some future date to recover deeper seams. The closest coal seam below the Wadge seam iS the Wolf Creek seam with an interburden thickness of approximatety 150 feet. There is no equipment suited to the terrein at Yoast that could economically remove overburdenfinterburden to such depths. However, there is an area of Wolf Creek coal that is recoverable at depths of less than 100 feet. Over the life of the Yoast Mine, various mining methods, in addition to the dragline, have been tried in order to maximize coal resource conservation and recovery. These methods have included stripping with dozers and scrapers where applicable and attempts to recover deeper coal using angering and/or highwall mining methods. Auger and highwall methods were used with limited success and are no longer part of the mine plan. The past angering and highwall mining methods/plans am addressed in Attachments f2-1 and 12-2, respectively. The remaining recoverable reserve (Wadge and Wolf Creek seams) will be mined with the 650 dragline. The areas mined and the remaining areas to be mined are shown on Exhibit 12-1, Operations Plan-Mining. • PR-02 5 Revised 10/05