Laserfiche WebLink
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 liner(s). <br />The reaming technique utilizes an inverted disc cutter equipped hemispherical raise -bore head, to cut the rock. During <br />drilling of the pilot hole(s) and reaming of the final shaft bore(s), all cuttings will be removed using an airlift system, <br />with water (reverse circulation) being used as the circulation media. Supplemental water for drilling, and to adjust the <br />density of the drilling medium, may be supplied as needed, by hauling water from a nearby location where TCC's <br />holds valid existing water rights. The cuttings will be placed in 70 x 100 x 8 foot lined temporary cuttings pit <br />excavated within the shaft pad adjacent to the shaft excavation. The cuttings pit will be lined with a nominal 30 -mil <br />PVC flexible membrane liner having a permeability of _10-12 cm/sec. Within the cuttings pit, the rock cuttings are <br />separated or settled out and the water is allowed to drain back or is pumped back into the drillhole for re -use. The <br />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 TCC'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 />16 -Left Utility Borehole (TR11-78, MR12-260) <br />TC proposes to complete a new utility borehole, to be located over the 16 -Left (16LT) gateroads in the Western <br />Mining District (WMD). The utility borehole will initially serve as a conduit to transfer concrete from the surface <br />to the underground workings to provide supplemental support for an area where elevated geologic stresses were <br />encountered in the previous longwall panel. Subsequent to this initial use, it is anticipated that the borehole will be <br />retained and utilized as a supplemental utility borehole for transfer of concrete, gravel, or other materials to the <br />underground workings for use in the WMD. The proposed facilities will be accessed from the paved County Road <br />(RCR27), using the existing access for the 17 -Left Concrete Borehole (MRI 1-253), with a new light -use road to the <br />borehole pad location, as shown on Map 24 (4/4) and Figure 49Z -F1. <br />MR14-283 2.05-45.24 10/30/14 <br />