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maintain continuous upwazd pressure on the cutter head. As boring progressed, the cuttings were dropped <br />down the shaft bore and are recovered, transported, and placed in mined-out aeeas underground. An <br />altema[ive to transporting the cuttings to mined-out areas was included, which involved slurrying them <br />into the EMD sump, For this option, an underground line would be installed and the cuttings slurried to <br />the EMD and pumped behind the seals in ?-, 9- or 30-Right. Any underground development waste <br />cuttings not placed underground were transported to the surface via the existing conveyance system and <br />stored south and east of the Area 1 Pit. The overall cuttings volume was approximately 21,000 CY <br />(16,862 CY swelled by 25 percent). <br />Any excess cuttings discharged from the existing rack belt, where they were loaded into trucks and hauled <br />to the previously approved overburden storage area (see Map 24 for locations). This overburden storage <br />area is in a previausly disturbed area and within TCC's existing sediment control system. The averburden <br />storage area is located an a gentle slope to the south of the Area 1 Pit, These cuttings mixed with coal <br />during conveyance from the mine and therefore were typically washed to recover the coal. The cuttings <br />and coal comprised an estimated 5-10 percent of the monthly volume of low quality coal processed <br />through the wash-plant. The cuttings then became pan of the refuse stream coming from the plant. The <br />fines generated during the washing process of the cuttings/coal were discharged underground as part of <br />the thickener underflow. The couzse fraction was placed in the refuse pile. Given the fact that the fines <br />from the cuttingslcoal were processed through the plant and the fines disposed of underground in the <br />thickener underflow, it was not necessary to conduct a geotechnical analysis of the material going to the <br />refuse pile. The fine fraction was the reason for committing to conducting a geotechnical analysis, but <br />they no longer will be placed in the refuse pile. <br />TCC test-washed some of the cuttings from the ventilation shaft boring but found it not to be very <br />efficient. Based on this, TCC generally hauled the remainder of the borings, unless they contain <br />significant amounts of coal, to the refuse pile for disposal. A geotechnicaI analysis of the cuttings was <br />performed by NWCC and a copy of the resulting report is presented in Exhibit 25a-2. It demonstrates that <br />the cuttings can be placed in the refuse pile without adversely impacting stability, <br />Once the cutter-head broke-through to the surface within the shaft collaz, the cutter-head, drive unit, and <br />temporary headframe were disassembled and removed from the site. A permanent sha8 casing consisting <br />of steel ring-beams and liner-plate was placed, and the annulus between the liner and the shaft bore was <br />cemented in segments. <br />The cement shaft Liner serves to isolate the Twentymile Sandstone from the Wedge Overburden. <br />Additionally, the Twentymile Sandstone was pressure-grouted to prevent seepage into the shaft. This <br />provides further assurance that, after final closure, the water in this unit wll2 he confined and not seep <br />down on the inside of the shaft. Following completion of shaft boring and casing operations and removal <br />of equipment from the site, the fan enclosure (fan shroud) and electrical control building were erected on <br />the previously constructed concrete pads, and the fan, fan drive motor, and electrical control, monitoring, <br />and communication systems were installed. Average pad thiclasess is 2 feet and total pad surface area is <br />approximately 3100sf. The insta}led axial-vane exhausting ventilation fan has a capacity of 800,000 efm <br />with a 3,000 hp drive motor. A fence was constructed to enclose the fan installaGan. Following <br />commissioning, the shaft pad site and access road were cleaned-up and surface areas graded and dressed. <br />In additian to the main vent shaft, up to two additional holes were cased to allow for power drops and <br />other ancillary uses into the mine. The two holes were cased to an internal nominal diameter of 4 and S <br />inches, One of the cased holes was used as a pressure relieflaccumulator for the production mine water <br />system System pressure relief and back-up were designed to prevent any surface discharge of production <br />mine water, however, a catastraphic failure of both primary and back-up pressure relief valves resulted in <br />a discharge in mid-2005. A manual ball valve was installed at that time to seal the casing and prevent any <br />future discharge, if suitable system pressure relief controls can be installed to assure that no discharge <br />will occur, the manual valve may be removed ar replaced with afail-safe valve that would allow for free <br />Thos-ss 2.os-as.2 cane/os <br />