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West Elk Mrne <br />. The Box Canyon pemut revision azea encompasses the remainder of the Box Canyon lease tract. Only <br />B Seam mining is planned in this area. <br />West Flatiron Mining Area -- This azea is designated on Map lA and includes extensions of longwall <br />panels 18A, 18, and 19. <br />South of Divide Mining Area -The mining area encompasses the E Seam longwall panels located <br />primarily in Sections 32, 33, and 34 of Township 13 South, Range 90 West of the 6th Principal <br />Meridian, and Sections 3, 4, and 5 of Township 14 South, Range 90 West of the 6th Principal <br />Meridian. The panels are identified as E 1 through E9. <br />South of Divide Permit Revision Area -The permit revision area is indicated by the regulatory <br />boundary added to the mine permit, as shown on Map lA. <br />Critical Mining Width -The width of a mining panel necessary for maximum subsidence to occur; <br />the length of the panel must also be greater than, or equal to, critical panel width for maximum <br />subsidence to occur. Critical width (Wer) commonly ranges from 1.0 to 1.4 times the overburden <br />depth (d). <br />Subcritical Mining Width -The width of a mining panel less than critical width (i.e., less than 1.0 to <br />1.4d). <br />Supercritical Mining Width -The width of a mining panel greater than critical width. <br /> <br /> <br />Table 42 <br />Definition of Subsidence Terms <br />S mbol Definition Dimensions <br />S Vertical Dis lacement Subsidence L <br />S,~ Maximum Vertical Di lacement S =a~[ L <br />S/S,~ Ratio of Vertical Displacement to Maximum Vertical <br />Dis lacement L/I. <br />Sh Horizontal Dis lacement L <br />t Coal Extraction Thickness L <br />a- S t Subsidence Factor L2 <br /> Subsidence Factor above Chain Pillars L2 <br />S = a Maximum Subsidence Above Chain Pillars L <br />d Overburclen D th L <br />S d Ratio of maximum vertical dis lacement to overburden d th L/L <br />W Critical Extraction Width L/L <br />W/d Minin Width to Overburden D th Ratio L2 <br />M Tilt Sloe L2 <br />Mm Maximum Tilt L2 <br />C Curvature, the reci rocal of Radius of Curvature rad/I. 1/L <br />C Maximum Curvature rad/I. 12 <br />E Horizontal Strain (+) is Positive, (-) is Negative L/L <br />Em Maximum Horizontal Strain L2 <br />~ Angle of Draw Degrees <br />B Break An le De ees <br /> Angel of Major Influence Degrees <br />r Radius of Major Influence L <br />1.05-l OS Revised Juue 2005 PRIG, Rev. March 2006; Rev. Apri11006 PR70; May 1006 PRIG <br />