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and drilling fluids are generally re-circulated. Shaft boring and casing of the approximate 20' diameter <br />ventilation shaft aze conducted as separate operations. Asurface-mounted drive unit is used to tum a <br />rotary cutting head attached to a shaft extending from the surface through the pilot hole, and a hoist on the <br />temporary headframe is used to maintain continuous upwazd pressure on the cutter head. As boring <br />progresses, the cuttings aze dropped down the shaft bore and aze recovered, transported, and placed in <br />mined-out azeas underground. An alternate to transporting the cuttings to mined-out azeas will be to <br />slurry them into the EMD sump. An underground line will be installed and the cuttings slurried to the <br />EMD and pumped behind the seals in 7, 9 or 10 Right. If the underground development waste cuttings are <br />not placed underground they will be transported to the surface via the existing conveyance system and <br />then will be stored south of the old pit. The cuttings volume will be approximately 21,000 cy (16,862 cy <br />swelled by 25%). The cuttings will dischazge off of the existing rock belt where they will be loaded into <br />trucks and hauled to the previously approved overburden storage area (see Map 24 for locations). This <br />overburden storage area is in a previously disturbed site and within TCC's existing sediment control <br />system. The overburden storage azea is located on a gentle slope to the south of pit 1 (old pit). These <br />cuttings were mixed with coal during conveyance from the mine and therefore will be washed to recover <br />the coal. It is anticipated the cuttings and coal will comprise 5 - 10% of the monthly volume of low <br />quality coal processed through the wash plant. The cuttings will then be part of the refuse stream coming <br />from the plant. The fines generated during the washing process of the cuttings/coal will be discharged <br />underground as part of the thickener underflow. The course segment will be placed in the refuse pile. <br />Given the fact that the fines from the cuttings/coal will be processed through the plant and the fines <br />disposed of underground in the thickener underflow it is not necessary to conduct a geotechnical analysis <br />of the material going to the refuse pile. The fine segment was the reason for committing to conducting a <br />geotechnical analysis, but they no longer will be placed in the refuse pile. <br />TCC has washed some of the cuttings from the ventilation shaft boring but has found it not to be very <br />efficient. Based on this TCC is planning to haul the remainder of the borings, unless they contain <br />significant amounts of coal, to the refuse pile for disposal. A geotechnical analysis of the cuttings was <br />performed by NWCC and a copy of the reports is presented in Exhibit 25a-2. It demonstrates that the <br />cuttings can be placed in the refuse pile without impacting its stability. <br />Once the cutter head breaks through to the surface within the shaft collar, the cutter head, drive unit, and <br />temporary headframe will be disassembled and removed from the site. A permanent shaft casing <br />consisting of steel ring beams and liner plate will be placed and the annulus between the liner and the <br />shaft bore will be cemented in segments after boring operations progressed to the surface. <br />The cement shaft liner will serve to isolate the Twentymile Sandstone from the Wadge Overburden. <br />Additionally, it is planned to pressure grout the Twentymile Sandstone to prevent seepage from it into the <br />shaft. This will further ensure that after final closure the water in this unit will be confined and not seep <br />down on the inside of the shaft. Following completion of shaft boring and casing operations and removal <br />of equipment from the site, the fan enclosure (fan shroud) and electrical control building will be erected <br />on either the previously constructed or new concrete pads and the fan, fan drive motor, and electrical <br />control, monitoring, and communication systems will be installed. Average pad thickness will be 2' and <br />total pad surface area will be approximately 3100sf. The installed axial-vane exhausting ventilation fan <br />has a capacity of 800,000 cfin with a 3000 hp drive motor. A fence will be constructed to enclose the fan <br />installation. Following commissioning, the shaft pad site and access road will be cleaned-up and surface <br />areas graded and dressed <br />In addition to the main vent shaft, up to two additional holes will be cased to allow for power drops and <br />other ancillary uses into the mine. If two holes are cased they will have an intemal nominal diameter of 4 <br />and 8 inches, and if only one hole is cased it will have a nominal internal diameter of 13". When the holes <br />MR 03-182 2.05-45.2 02/25/03 <br />