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system, with water (reverse circulation) being used as the circulation media. Supplemental water, for drilling and
<br />to adjust the density of the drilling medium, may be supplied, as needed, by hauling water from a nearby location
<br />where TCC's holds valid existing water rights. The cuttings will be placed in 115 x 425 x 10 foot, four cell, lined
<br />temporary cuttings pit excavated within the shaft pad adjacent to the shaft excavation. The cuttings pit will be lined
<br />with a nominal 30 -mil PVC flexible membrane liner having a permeability of _10 -12 cm/sec.
<br />The cutting head will be 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 the
<br />hole and is tensioned to adjust the cutting weight on the head and to keep the drill pipe straight. The cutting head
<br />moves the water from near the center of the head and discharges it at the periphery of the head. This water then flows
<br />down around the cutters and washes the cuttings towards the pick -up pipe in the center of the head. The drill pipe's
<br />upward flow is activated by compressed air injected down the center of the drill pipe. Rock cuttings are moved by the
<br />circulation of the water down the hole, across the shaft bottom and up the drill pipe to the surface collection pit.
<br />Within the collection pit, the rock cuttings are separated or settled out and the water is allowed to drain back or is
<br />pumped back into the hole for re -use. The cuttings volume will be approximately 12,500 cy.
<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 -foot inside diameter
<br />using a hydrostatic steel liner. The steel liner sections will be pre- fabricated off -site, hauled to the site and field
<br />welded in 30 -50 foot joints. The liner will be floated into place. This is accomplished by securing a steel bulkhead
<br />to the bottom joint and leaving the excavated hole full of water while the liner is being lowered into place. By
<br />calculating the buoyancy of the liner, and adding water to the capped liner column, as needed, the liner is easily and
<br />safely lowered into position. Once the liner is in place, a nominal 9 -inch thick grout seal will be pumped between
<br />the strata and liner. The grouted steel liner will serve to isolate the Twentymile Sandstone from the Wadge
<br />Overburden. As previously noted, TCC plans to pressure grout the Twentymile Sandstone to minimize seepage to
<br />the shaft. This will help assure that, after final closure, groundwater from this unit will be confined and not seep
<br />down the inside of the shaft.
<br />Upon completion of shaft drilling and steel liner installation for both shafts, the cuttings pit will be dewatered.
<br />Excess water will be hauled to the Area 1 Pit, and the remainder will be allowed to evaporate. After dewatering the
<br />cuttings pit and allowing the cuttings to consolidate and dry-out, the collection pit and cutting materials will be
<br />covered with stockpiled materials from the shaft collar excavation, graded and revegetated with a temporary cover.
<br />A sign(s) will be posted designating the temporary mine development waste pit. The cuttings and shaft collar
<br />excavation materials will be utilized to re -fill the shafts during eventual reclamation of the shaft installation.
<br />As shown on Map 23, additional entries will be driven from the 18 -Left gate -road to the north to connect with the
<br />two ventilation shafts. The entries will be driven in the same manner as is used in TCC's development work, i.e.
<br />continuous miners and shuttle cars.
<br />Following completion of shaft boring and casing operations and removal of the drilling equipment from the site,
<br />emergency hoist equipment, consisting of an escape capsule, hoist derrick, hoist drive unit, control equipment and
<br />18 x 24 foot pre- fabricated metal hoist house, and a pre- fabricated propane -fired shaft heater and ducting will be
<br />erected/installed on the previously constructed intake shaft concrete pad. The shaft heater will be connected to a
<br />propane supply tank, mounted on prefabricated concrete saddles, and a buried electrical cable. A chain -link
<br />security fence with a locked gate will be constructed to enclose the intake shaft and emergency hoist installation.
<br />Similarly, a fan enclosure (fan shroud), silencer, and electrical control building will be erected on the previously
<br />constructed exhaust shaft concrete pad, and the fan, fan drive motor, and electrical control, monitoring, and
<br />communication systems will be installed. It is presently anticipated that the 400 hp, 90,000 cubic -foot per minute
<br />Robinson Fan and associated equipment will be relocated to the 18 -Left Ventilation Shaft from the EMD
<br />Ventilation Shaft location. In order to comply with new Mine Atmosphere Control (MAC) regulations, the cased
<br />nitrogen injection borehole will be connected to one or more manifolded pipe systems underground which will
<br />connect to sealed gob areas. At the surface, an 8 -foot diameter culvert manhole may be installed around the cased
<br />borehole(s) as a well -head, with appropriate grounding and lightning protection to meet MSHA requirements. The
<br />fixed pipeline(s) will connect at the surface to a portable skid - mounted nitrogen generator, which will operate in
<br />conjunction with associated portable compressors and controls. Required power for this installation will be
<br />provided by dropline from the existing 18 -Left Substation.
<br />MR10 -249 2.05-45.18 11 /01 /10
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