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Primary Method of Construction — Blind Drilling — The potential exists to complete either one 48 -inch shaft or two <br />30 -inch shafts. Prior to blind drilling, a shaft collar(s), up to 8 -foot in diameter will be excavated to competent <br />rock, at a depth of approximately 60 feet. Material from the collar excavation will be placed within and on either <br />end of the cuttings pit. Surface casing up to 7 feet in diameter (inside) and large enough to accept the shaft casing <br />and drilling tools will be installed in the shaft collar(s). This surface casing will be either steel casing grouted in- <br />place or cast -in -place concrete. Maximum 18 -inch diameter auger holes will be advanced into competent material, <br />and reinforced concrete piers will be poured to anchor the shaft pads and any other significant structures. It is <br />anticipated that up to 10 anchor piers may be required. A "T" shaped concrete pad will be poured to accommodate <br />the drilling and casing equipment for the ventilation intake shaft. Average thickness for the reinforced concrete pad <br />will be 2 feet, and the pad will be a maximum of 770 square feet. Specialized blind drilling equipment consisting <br />of an A -leg derrick, drive motor, and drill -string handling components will be installed on the shaft pad and used to <br />drill the pilot hole(s) and, complete shaft drilling. <br />A nominal pilot hole(s) of up to 17.5 -inch diameter will be drilled for the shaft(s) to an approximate depth of 1,200 <br />feet and surveyed to determine vertical shaft deviation and location underground for mine entry tie -ins. The pilot <br />hole(s) will then be reamed to a nominal diameter of either 3.5 feet or 5.5 feet to accommodate the final steel <br />liner(s). The reaming technique utilizes an inverted disc cutter equipped hemispherical raise -bore head, to cut the <br />rock. During drilling of the pilot hole(s) and reaming of the final shaft bore(s), all cuttings will be removed using <br />an airlift system, with water (reverse circulation) being used as the circulation media. Supplemental water for <br />drilling, and to adjust the density of the drilling medium, may be supplied as needed, by hauling water from a <br />nearby location where TCC's holds valid existing water rights. The cuttings will be placed in 70 x 100 x 8 foot <br />lined temporary cuttings pit excavated within the shaft pad adjacent to the shaft excavation. The cuttings pit will be <br />lined with a nominal 30 -mil PVC flexible membrane liner having a permeability of _10 -12 cm/sec. Within the <br />cuttings pit, the rock cuttings are separated or settled out and the water is allowed to drain back or is pumped back <br />into the drillhole for re -use. The maximum collar excavation and cuttings volume will be approximately 1,200 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(s) will then be lined to a nominal 2.5- or 4 -foot inside <br />diameter using a hydrostatic steel liner(s). The steel liner sections will be pre - fabricated off -site, hauled to the site <br />and field welded in 30 -50 foot joints. The liner(s) will be floated into place. Once the liner(s) is in place, a <br />nominal 6- to 9 -inch thick grout seal will be pumped between the strata and liner(s). The grouted steel liner(s) will <br />serve to isolate the Twentymile Sandstone from the Wadge Overburden. <br />Upon completion of shaft drilling and steel liner installation for the shaft(s), 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 15 -Left gate -road to the south to connect with the <br />ventilation shaft(s). The entries will be driven in the same manner as used in TLC's development work, i.e. <br />continuous miners and shuttle cars. <br />Following commissioning, the shaft pad site and light -use road will be cleaned -up and surface areas graded and <br />stabilized by seeding with the temporary seed mixture. An 8.625 -inch (outside) diameter pipe will be connected to <br />the wall of the shaft liner for use as a rock -dust drop. The new 15LT Rock -Dust Installation will consist of a new <br />rock -dust tank, which will be mounted on four poured concrete piers; a connection to the rock -dust drop pipe; <br />required electrical and control equipment; and a dust collection system. A security fence with locked gate and <br />appropriate signage will be installed around the shaft opening to limit access to authorized personnel. <br />When these facilities are no longer needed to support ongoing or future mining and related operations, reclamation <br />will involve removal of surface structures and facilities, demolition of concrete foundations and pads, disposal of <br />concrete debris in the shafts, replacement of cuttings from the temporary cuttings pit in the shaft, plugging and <br />sealing of the shaft in accordance with applicable State Engineer requirements, grading of disturbance areas to <br />blend with the surrounding terrain, soil material replacement, and reseeding with the permanent Rangeland <br />revegetation seed mixture. <br />MR12 -260 2.05-45.25 04/12/12 <br />