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A shaft collar was excavated to an approximate 20- to 22-foot diameter to competent rock at a depth of <br />approximately 20-25 feet. Material from the collar excavation was placed within the waste disposal pit. A <br />surface casing approximately 12-18 feet in diameter (inside) and large enough to accept the shaft casing <br />and conventional drilling and mucking tools was installed in the shaft collar. This surface casing is cast-in- <br />place concrete. A nominal 25- by 25-foot by 4- to 6-foot thick concrete pad was then poured to <br />!accommodate the winches, drilling, mucking and casing equipraient, and headframe. Specialized drilling <br />and mucking equipment in the form of a hoist, headframe, backleg foundation, and muck dumping system <br />was used to excavate the shaft. An additional concrete pad(s); nominal size of 40 by 100 feet by 2 feet <br />thick, was poured to accommodate the hoisting winch, transformers, distribution boxes, operator consoles, <br />surrounding building, and other miscellaneous equipment. <br />Shaft excavation was completed as a progressive cyclic operation, with each excavation cycle consisting of <br />four basic operations; drilling, blasting, mucking, and concrete lining. Drilling involved the use of one or <br />more pneumatic shaft jumbo drills nested in a multiple-deck woik stage. Blasting was completed using <br />permissible stick powder and electric detonators. The blasted shaft material was mucked using in-shaft <br />pneumatic muckers and a nominal 3-4 yard hoisting bucket. The shaft cuttings were placed by a wheel- <br />loader in a 14-foot deep, lined temporary mine development waste pit excavated within the shaft pad, <br />adjacent to the shaft excavation, as shown on Maps EX16E-M1 and M2. The cuttings pit is lined with a ' <br />nominal 30-mil PVC flexible membrane liner having a permeability of -10~1z cm/sec: The PVC liner is <br />covered with approximately6-8 inches of pit-run material to protect the liner. <br />The shaft concrete lining was placed in nominal 20- to 30-foot lifts in cycle with the drilling and mucking <br />operation, using acurb-ring and slip-form assembly. During excavation, the shaft work area was ventilated <br />using ventilation ducting and a permissible surface fan. Once the blind sink excavation reached the coal <br />seam, the work stage was removed and disassembled. <br />The cuttings volume generated by shaft sinking operations is approximately 15,126 cubic yards (22,690 <br />cubic yards when swelled by 50 percent, based on 20-foot diameter and 1,300-foot depth). If drainage of <br />water from the excavated material resulted in any significant accumulation of water in the cuttings pit, the <br />water was pumped to a water tanker to maintain essentially dry conditions in the pit. Upon completion of <br />the shaft excavation and concrete liner installation, any minor water accumulation in the cuttings pit were <br />allowed to dry-out, and the collection pit and cutting materials were then be covered with previously <br />placed materials from the shaft collar excavation, graded, and revegetated with a temporary cover. A <br />sign(s) was posted designating the temporary mine development waste pit. The cuttings and shaft collar <br />excavation materials will be utilized to re-fill the shaft during eventual reclamation of the facility. <br />The cement liner serves to isolate the Twentymile Sandstone from the Wadge Overburden. As noted <br />above, apre-grout program is not required in a conventional blind sink. A probe-hole is typically carried <br />down the hole as the shaft is excavated. Water is grouted off from within the excavated shaft as it is <br />encountered. This further assures that, after final closure, the water in this unit is confined and will not <br />seep down on the inside of the shaft. Following completion of shaft excavation and cement lining <br />operations, and removal of equipment from the site, an escape elevator will be installed within the shaft. <br />As an alternate escape method, an emergency hoisting system may be erected in lieu of [he escape elevator <br />on either the previously constructed or a new concrete pad. A fence was constructed to enclose the surface <br />collar and escape elevator/emergency hoist installation. <br />Undereround Utilities Project Components: <br />Concurrent with road construction, a 69-KV power distribution line was extended from the existing <br />substation at the Northwest Mains fan location to apad-mounted transformer at the 6-Main North shaft <br />site. The power distribution line is approximately 3,130 feet long with a total of approximately 14 <br />MR06-212 2.05 - 45.6d 10/31/06 <br />