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,~FEB.2~J.2002 5~44PM <br />TWENTYMILE CORL ENVIRONMENTRL <br />N0.475 <br />P.6 <br />previously disturbed site and within TCC's existing sediment control system, The overburden storage area is <br />located on a gentle slope to the south of the pit I. They will be used in the final regarding of the surface facilities <br />area. Once the cutter head breaks through to the surface within the shaft collaz, the cutter head, drive unit, and <br />temporary headfrune will be disassembled and removed from the site. A permanent shaft casing <br />consisting of steel ring besets aad liner plate will be placed and the annulus hetween the liner and the shaft bore <br />will be cemented in segments after boring operations progressed to the surface. <br />The cement shaft liner will serve to isolate the Twentymile Sandstone from the Wedge Overburden. Additionally, it <br />is planned to pressure grout the Twentymile Sandstone to prevent seepage from it into the shaft. This will further <br />ensure that after final closure the water in this unit will be confined and not seep down an the inside of the shaft. <br />Following completion of shaft boring and casing operations and removal of equipment from the site, the fan <br />enclosure (fan shroud) and electrical control building will be erected on either the previously constructed or new <br />concrete pads aad the fan, fan drive motor, and electrical control, monitoring, and communication systems will be <br />installed. Avorage pad thickness will be 2' and total pad surface area will be approximately 3100sf, The installed <br />axial-vane exhausting ventilation fen has a capacity of 800,000 cfm with a 3000 by drive motor. A fence will be <br />constructed to enclose the fan installation. Following commissioning, the shaft pad site and access road will be <br />cleaned-up and surface areas graded and dressed <br />Concurrent with road construction a power distribution line will be extended from the existing substation to the <br />pad.mounted transformer at the shaft site. The power distribution line ie approximately 3,600' long with a total of <br />12 power poles. <br />In order to minimize potential environmental and aesthetic impacts associated with the NW Mains ventilation shaft <br />and fan installation, surface drainage at the shaft site will be handled by an upgradient diversion ditch, perimeter <br />banns, and gravel surfacing under an SAB, the limited road drainage will ba handled by designed drainage <br />structures, active use areas are graveled to control dust and drainage, other disturbed areas (including topsoil <br />stockpiles) will he stabilized with temporary vegetation, and structures will be painted in neutral earth-tone colors <br />to blend with the natural surroundings. <br />As shown on Map 23, additional entries will be driven to the north from the ventilation shaft site. These emries will <br />be Headed to maximize the efl7cieacy of the ventilation system. The entries will be driven in the same manner as is <br />used in TCC's development worly f,e, continuous miners and shuttle care, <br />No. 7 North Escape 8baft [Section 20. TSN. I2$6Vhi <br />'A 1,066 foot escape borehole shaft was constructed into #7 entry ofNortb Maine to allow emergency evacuation of <br />ersnnnel from the development sections of the 9 Right and 10 Right gateroads. The construction of the shag <br />tilized raise drilling techniques. It is anticipated that the escape shaft will be utilized for approximately ten years. <br />e site is shown on Figure 23, General Location of Escape Shaft, <br />e drilling of the shaft resulted in minimal surface disturbance. A drill pad approximately 200' x 200' was <br />constructed at the resulting site is 1,450 CY of cut and 611. Available topsoil was salvaged and stockpiled for <br />~ture reclamation of the site immediately northeast of the drilled pad. Approximately 18°' of topsoil derived from <br />ochetapa Loam is available for salvaging (222 CY). Casing and other drilling sgpplies were stockpiled on the <br />bore) ole pad. <br />After topsoil removal, two mud pits with dimensions of 10' x 10' x 7.5' were dug adjacent to the drill hole. <br />Drilling fluids and cuttings ware discharged into the adjacent pits, allowing settling In one pit with water decanting <br />into the adjacent pit, Drilling muds were used during the course of drilling rho surface collaz and pilot hole. The <br />surf~Ce coAar was approximately 5.0 feet in diameter, and the pilot hole was 11 inches in diameter, <br />MR 02-176 2.05-45.2 02/20/02 <br />