2014-04-25_PERMIT FILE - C1982056A (3)

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located on a gentle slope to the south of the Area 1 Pit. These cuttings mixed with coal during conveyance from the mine and therefore were typically washed to recover the coal. The cuttings and coal comprised an estimated 5 -10 percent of the monthly volume of low quality coal processed through the wash - plant. The cuttings then became part of the refuse stream coming from the plant. The fines generated during the washing process of the cuttings /coal were discharged underground as part of the thickener underflow. The course fraction was placed in the refuse pile. Given the fact that the fines from the cuttings /coal were processed through the plant and the fines disposed of underground in the thickener underflow, it was not necessary to conduct a geotechnical analysis of the material going to the refuse pile. The fine fraction was the reason for committing to conducting a geotechnical analysis, but they no longer will be placed in the refuse pile. TCC test - washed some of the cuttings from the ventilation shaft boring but found it not to be very efficient. Based on this, TCC generally hauled the remainder of the borings, unless they contain significant amounts of coal, to the refuse pile for disposal. A geotechnical analysis of the cuttings was performed by NWCC and a copy of the resulting report is presented in Exhibit 25a -2. It demonstrates that the cuttings can be placed in the refuse pile without adversely impacting stability. Once the cutter -head broke - through to the surface within the shaft collar, the cutter -head, drive unit, and temporary headframe were disassembled and removed from the site. A permanent shaft casing consisting of steel ring -beams and liner -plate was placed, and the annulus between the liner and the shaft bore was cemented in segments. The cement shaft liner serves to isolate the Twentymile Sandstone from the Wadge Overburden. Additionally, the Twentymile Sandstone was pressure - grouted to prevent seepage into the shaft, providing further assurance that, after final closure, the water in this unit will be confined and not seep down on the inside of the shaft. Following completion of shaft boring and casing operations and removal of equipment from the site, the fan enclosure (fan shroud) and electrical control building were erected on the previously constructed concrete pads, and the fan, fan drive motor, and electrical control, monitoring, and communication systems were installed. Average pad thickness is 2 feet and total pad surface area is approximately 3100sf. The installed axial -vane exhausting ventilation fan has a capacity of 800,000 cfm with a 3,000 hp drive motor. A fence was constructed to enclose the fan installation. Following commissioning, the shaft pad site and access road were cleaned -up and surface areas graded and dressed. In addition to the main vent shaft, up to two additional holes were cased to allow for power drops and other ancillary uses into the mine. The two holes were cased to an internal nominal diameter of 4 and 8 inches. One of the cased holes was used as a pressure relief /accumulator for the production mine water system. System pressure relief and back -up were designed to prevent any surface discharge of production mine water, however, a catastrophic failure of both primary and back -up pressure relief valves resulted in a discharge in mid -2005. A manual ball valve was installed at that time to seal the casing and prevent any future discharge. If suitable system pressure relief controls can be installed to assure that no discharge will occur, the manual valve may be removed or replaced with a fail -safe valve that would allow for free movement of air in the pressure relief /accumulator pipe but prevent fluid discharge, at some point in the future. So long as no discharge is anticipated or occurs, the provisions of Rule 4.05.2 are not applicable. The 4 -inch cased borehole has been disconnected from the mine water system, and will be used as a rock -dust drop borehole. TC proposes to install an additional rock -dust tank over this existing borehole to supply rock -dust for rock - dusting of the main entries and adjacent mine working areas. The proposed rock -dust tank installation is within the existing NWM Ventilation Fan surface disturbance area, and will involve no new or incremental disturbance. The NWM Rock -Dust Tank Installation will consist of a re -used rock -dust tank from the Empire Mine property, which will be mounted on four 24 -inch diameter poured concrete piers extending approximately 22 feet below ground level; a 5 x 5 x 1 foot concrete pad with baghouse dust collector unit; a connection to the existing borehole; required electrical and control equipment, and 3 new powerpoles for a 280 -foot distribution line that will tie -in to the existing NWM Substation (Primary Substation 12). The additional rock -dust tank installation can be readily accessed from the NWM Ventilation Fan pad area and the existing NWM /6MN Light -Use Road. Drainage for the existing NWM Ventilation Fan Installation is controlled by an existing Small -Area Exemption, and the proposed rock -dust tank installation will not modify the drainage configuration or requirements. MR10 -247 2.05 -45.2 09/24/10