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A 48' by 24' concrete T-shaped pad will then be poured to accommodate the drilling and casing equipment. <br />Specialized blind drilling equipment in the form of an A-leg derrick will be used to drill the pilot hole and <br />excavate the shaft. A nominal 17-I/2" pilot hole will then be drilled to an approximate depth of 1,000' and <br />surveyed to determine vertical shafr deviation and location underground for mine entry tie-ins. The pilot hole <br />will then be reamed to a nominal diameter of 7.5' to accommodate the final steel liner. The reaming technique <br />utilizes an inverted disc cutter equipped hemispherical raise bore head to cut the rock. During the drilling of the <br />pilot hole and the 7.5' diameter excavation, all cuttings will be removed from the excavation using an airlift <br />system, with water (reverse circulation) being the circulation media. The cuttings will be placed in a 200' x <br />100' x 10' deep, lined temporary mine development waste pit excavated within the shaft pad adjacent to the <br />shaft excavation, as shown on Map I W. The cuttings pit will be lined with a nominal 30-mil PVC flexible <br />membrane liner having a permeability of~10-72 cm/sec. <br />The cutting head is rotated from the surface by the drill pipe, which also serves as a conduit to transfer cuttings <br />from the shaft bottom to the surface collection pit. The drill pipe also serves to suspend the drilling assembly in <br />the hole and is tensioned to adjust the cutting weight on the head and to keep the drill pipe straight. The cutting <br />head moves the water from near the center of the head and discharges it at the periphery of the head. This water <br />then flows down around the cutters and washes the cuttings towards the pick-up pipe in the center of the head. <br />The drill pipe's upward flow is activated by compressed air injected down the center of the drill pipe. Rock <br />cuttings are moved by the circulation of the water down the hole, across the shaft bottom and up the drill pipe to <br />the surface collection pit. Within the collection pit, the rock cuttings are separated or settled out and the water is <br />allowed to drain back or is pumped back into the hole for re-use. <br />The cuttings volume will be approximately 1,650 cy (2,475 cy when swelled by 50 percent). Upon completion <br />of the shaft excavation and steel liner installation, the cuttings pit will be dewatered. All water will be hauled to <br />the old pit to the south of TCC's overland conveyor. The collection pit and cutting materials will then be <br />covered with previously placed materials from the shaft collar excavation, graded and revegetated with a <br />temporary cover. A sign(s) will be posted designating the temporary mine development waste pit. The cuttings <br />and shaft collar excavation materials will be utilized to re-fill the shaft during eventual reclamation of the <br />facility. <br />Once the cutter head reaches the coal seam, the cutter head will be disassembled and removed from the A-leg <br />derrick. Using the same A-leg derrick, the excavated shaft will then be lined to a nominal 6' inside diameter <br />using a hydrostatic steel liner. The steel liners will be pre-fabricated off site, hauled to the site and field welded <br />in 40' joints. The liner will be floated into place. This is accomplished by securing a steel bulkhead to the <br />bottom joint and leaving the excavated hole full of water while the liner is being lowered into place. By <br />calculating the exact buoyancy of the liner, and adding water to the inside diameter as needed, the liner is easily <br />and safely lowered into position. Once the liner is in place, a nominal 9" thick grout seal will be pumped <br />between the strata and liner to hold it in place. <br />The grouted steel liner will serve to isolate the Twentymile Sandstone from the Wadge Overburden. As noted <br />above, it is planned to pressure grout the Twentymile Sandstone to prevent seepage from it into the shaft. This <br />will further assure that after final closure the water in this unit will be confined and not seep down on the inside <br />of the shaft. Following completion of shaft boring and casing operations and removal of equipment from the <br />site, the emergency hoist equipment will be erected on either the previously constructed or a new concrete pad. <br />Average pad thickness will be 1-2' and total pad surface area will be approximately 800 FtZ. A fence will be <br />constructed to enclose the surface collar and emergency hoist installation. Following commissioning, the shafr <br />pad site and access road will be cleaned-up and surface areas graded and dressed. <br />In order [o minimize potential environmental and aesthetic impacts associated with the 18 Right ventilation shaft <br />and emergency hoist installation, surface drainage at the shafr site will be handled by two (2) up-gradient <br />diversion ditches, two (2) down-gradient drainage ditches, the use of 20-inch diameter sediment logs around the <br />lower portion of the topsoil stockpile, the use of Curlex single net (Curlex I) erosion control blankets over <br />seeded cut and fill slopes, the combination of a rock filter (2-ft rock berm) and grass filter, and gravel surfacing <br />under an SAE (Refer to Exhibit 8T for SAE detail). The limited road drainage will be handled by designed a <br />design road ditch and drainage structures. Active use areas will be graveled to control dust and drainage, other <br />MROS-192 2.05-45.5 03/22/05 <br />