2010-06-04_PERMIT FILE - C1982056A (9)

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The cutting head is rotated from the surface by the drill pipe, which also serves as a conduit to transfer cuttings from the shaft bottom to the surface collection pit. The drill pipe also serves to suspend the drilling assembly in the hole and is tensioned to adjust the cutting weight on the head and to keep the drill pipe straight. The cutting head moves the water from near the center of the head and discharges it at the periphery of the head. This water then flows down around the cutters and washes the cuttings towards the pick -up pipe in the center of the head. The drill pipe's upward flow is activated by compressed air injected down the center of the drill pipe. Rock cuttings are moved by the circulation of the water down the hole, across the shaft bottom and up the drill pipe to the surface collection pit. Within the collection pit, the rock cuttings are separated or settled out and the water is allowed to drain back or is pumped back into the hole for re -use. The cuttings volume will be approximately 1,650 CY (2,475 CY when swelled by 50 percent). Upon completion of the shaft excavation and steel liner installation, the cuttings pit was dewatered. All water was hauled to the old pit to the south of TCC's overland conveyor. After allowing the cuttings to consolidate and dry-out, the collection pit and cutting materials were covered with stockpiled materials from the shaft collar excavation, graded and revegetated with a temporary cover. A sign(s) was posted designating the temporary mine development waste pit. The cuttings and shaft collar excavation materials will be utilized to re -fill the shaft during eventual reclamation of the facility. Once the cutter head reaches the coal seam, the cutter head will be disassembled and removed from the A -leg derrick. Using the same A -leg derrick, the excavated shaft will then be lined to a nominal 6 -foot inside diameter using a hydrostatic steel liner. The steel liners will be pre- fabricated off -site, hauled to the site and field welded in 40 -foot joints. The liner will be floated into place. This is accomplished by securing a steel bulkhead to the bottom joint and leaving the excavated hole full of water while the liner is being lowered into place. By calculating the exact buoyancy of the liner, and adding water to the inside diameter as needed, the liner is easily and safely lowered into position. Once the liner is in place, a nominal 9 -inch thick grout seal will be pumped between the strata and liner to hold it in place. The grouted steel liner will serve to isolate the Twentymile Sandstone from the Wadge Overburden. As previously noted, TCC plans to pressure -grout the Twentymile Sandstone to minimize seepage to the shaft. This will help assure that, after final closure, groundwater from this unit will be confined and not seep down the inside of the shaft. Following completion of shaft boring and casing operations and removal of equipment from the site, the emergency hoist equipment will be erected on either the previously constructed or a new concrete pad. Average pad thickness will be 1 -2 feet, and total pad surface area will be approximately 800 sf. A fence will be constructed to enclose the surface collar and emergency hoist installation. A pre- fabricated propane -fired shaft heater and ducting will be installed on the existing concrete collar structure and connected to a skid- mounted propane tank and a buried electrical cable. Two additional powerpoles on the shaft pad will support a drop -line from the nearby Yampa Valley Electric Association power distribution line. Following commissioning, the shaft pad site and access road will be cleaned -up and surface areas graded and dressed. In order to minimize potential environmental and aesthetic impacts associated with the 18 -Right ventilation shaft and emergency hoist installation, surface drainage at the shaft site will be handled by two (2) up- gradient diversion ditches, two (2) down - gradient drainage ditches, the use of 20 -inch diameter sediment logs around the lower portion of the topsoil stockpile, the use of Curlex single net ( Curlex 1) erosion control blankets over seeded cut and fill slopes, the combination of a rock filter (2 -ft rock berm) and grass filter, and gravel surfacing under an SAE (Refer to Exhibit 8T for SAE detail). Drainage from the other topsoil stockpiles will be addressed by upslope diversion ditches to route upgradient run -on around the piles, silt fence or wattles at the downslope toe of the piles, and rock check dams where the upslope drainage meets the designed road ditches. The limited road drainage will be handled by a designed road ditch and drainage structures. Active use areas will be graveled to control dust and drainage, other disturbed areas (including topsoil stockpiles) will be stabilized with temporary vegetation, and any structures will be painted in neutral earth -tone colors to blend with the natural surroundings. As shown on Map 23, additional entries will be driven at the back of the 18 -Right gate road to the east to connect with the ventilation shaft. These entries will be needed to maximize the efficiency of the ventilation system. The entries will be driven in the same manner as is used in TCC's development work, i.e. continuous miners and shuttle cars. TR09 -66 2.05-45.6 02/17/09