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West Elk Mine <br />Room and Pillar Panels <br />F Seam room and pillar panels generally consisted of 6 to 8 entries driven on 60 to 100 foot <br />centers and with crosscuts on 60 to 120 foot centers. During secondary mining of the room and <br />pillar panels, additional rooms may have been developed on one or both sides of the initial <br />development. Sufficient barrier pillars were left to protect the main entries and bleeder entries (if <br />separate bleeders were utilized). During secondary mining, partial or full pillar extraction was <br />completed, depending on conditions in the panel. <br />Longwall Mining Methods <br />MCC uses longwall mining technology to mine the B and E Seams. Longwall panel layouts <br />consist of gate -roads driven by continuous miners, a longwall face about 1,100 foot wide, and <br />necessary ventilation and conveyor entries, and barrier pillars. <br />After the ventilation and gate -road entries are completed, a longwall set-up or start room is <br />driven at the far end of the panel. Longwall equipment is moved in and assembled. Once <br />equipment is ready, the longwall system mines the panel in a retreat fashion until it reaches the <br />main entry barrier pillar. The equipment is then disassembled and moved to another panel. <br />Longwall Gate -Roads <br />Room and pillar methods are used to develop gate -road entries for the longwall mining <br />equipment. Generally, two to five parallel entries are driven on 100 to 200 foot centers. A three - <br />entry yield abutment design has typically_ been used. The size and configuration of longwall gate <br />pillars is based on the regional geology, and depth of cover. Longwall panel barrier pillars are <br />left to protect main entries and bleeder entries. <br />Bleeder Entries <br />Bleeder entries were developed to ventilate active and previously mined longwall areas until <br />those areas were permanently sealed. Bleeder entries were connected to the main return air <br />ventilation system. In November 2009, the main mine ventilation system for the F seam and <br />southern B seam was converted to a blowing system that includes a "bleederless" ventilation <br />system resulting in each panel being progressively and/or completely sealed upon completion of <br />mining of that panel. <br />Barrier Pillars <br />A barrier pillar is a large block of solid coal left in place to protect active mine workings. Barrier <br />pillars are left between longwall panels and main entries, between submains and longwall panels, <br />or in other areas, as needed. Barrier pillars vary in size, and designs are based primarily on life - <br />expectancy and degree of protection required for the barrier. Design criteria include depth of <br />overburden, horizontal stresses, etc. In all cases, the dimensions of barrier pillars will be <br />adjusted for prevailing conditions, to provide the protection for which they are intended. <br />2.05-8 Rev. 11/04- PRII; 03/06- PRIG; 07/15- MR413 <br />