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Doc Date:1 211 112 0 0 1 <br /> <br />• <br />~~~ 4.10 COAL PROCESSING WASTE BANKS <br />4.10.1 GENERAL REQUIREMENTS <br />III IIIIIIIIIIIIIIII <br />sss <br />• <br />This section outlines the general performance standards required for <br />construction of coal processing waste banks within the permit area. <br />Specific requirements include: foundation design, material placement and <br />compaction, protection of hydrologic systems, general drainage <br />requirements, prevention of spontaneous combustion, general construction <br />specifications and inspection requirements. <br />The coal seams mined at the Southfield operations (Red Arrow and Jack <br />O'Lantern) contain substantial amounts of impurities such as sandstones, <br />shales and other rock or mineral matter which occur as inclusions or <br />partings within the mining zone. In order to produce a clean, high <br />quality coal product, raw coal produced within the mine is washed in the <br />coal processing facility shown on the Mine Surface Facilities Map, (Map <br />18) and described in Section 2.05.3, Operation Plan - Permit Area. This <br />facility uses gravity, differential settling, and centrifugal separation <br />techniques to separate impurities within the raw coal from the clean coal <br />product. These impurities, which amount to approximately 35 percent of <br />total mine production, are disposed of in accordance with the standards <br />outlined in this section in the permanent coal refuse stockpile shown on <br />the Mine Area Surface Facilities Map, (Map 18) and described in Section <br />2.05.3, Operation Plan - Permit Area. <br />The coal refuse pile was initially designed for Dorchester in 1980 and <br />1981 by Geo Testing Laboratories, Inc., a Colorado Springs based <br />geotechnical consulting firm. Subsequently, in response to increased coal <br />production and resulting increases in refuse disposal volumes, the <br />facility was reevaluated and re-designed by Rocky Mountain Geotechnical <br />(RMG), another Colorado Springs based geotechnical consulting firm. The <br />RMG report concluded that, with establishment of proper subdrainage, <br />placement of dewatered and mixed coarse and fine refuse in lifts no <br />greater than three (3) feet in thickness, and adequate surface drainage, <br />4.10-1 <br />