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West Elk Mine <br />South of Divide Minint? Area -The mining area encompasses the E Seam longwall panels <br />located primarily in Sections 32, 33, and 34 of Township 13 South, Range 90 West of the 6th <br />Principal Meridian, and Sections 3, 4, and S of Township 14 South, Range 90 West of the <br />6th Principal Meridian. The panels are identi£ed as El through E9. <br />South of Divide Permit Revision Area -The permit revision area is indicated by the <br />regulatory 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 <br />occur; the length of the panel must also be greater than, or equal to, critical panel width for <br />maximum subsidence to occur. Critical width (Wer) commonly ranges from 1.0 to 1.4 times <br />the overburden depth {d). <br />Subcritical Mining Width -The width of a mining panel less than critical width (i.e., less <br />than 1.0 to 1.4d). <br />Supercritical Mining Width -The width of a mining panel greater than critical width. <br />• <br />Table 42 <br />Definition of Subsidence Terms <br />S mbol Definition Dimensions <br />S VetticalDis lacement Subsidence L <br />Sm Maximum Vertical Di lacement S,~ a~t L <br />S/S,~ Ratio of Vertical Displacement to Maximum Vertical <br />Dis lacement L2 <br />Sh Horizontal Di lacement L <br />t Coal Extraction Thickness L <br />a S [ Subsidence Factor L2 <br /> Subsidence Factor above Chain Pillars L2 <br />S - •[ Maximum Subsidence Above Chain Pillars L <br />d Overburden D th L <br />S,e/d Ratio of maximum vertical dis lacement to overburden d th L2 <br />W Critical Extraction Width L/L <br />W/d Minin Width to Overburden ih Ratio L2 <br />M Tilt Sloe L2 <br />M Maximum Tilt L2 <br />C Curvature, the reci mcal of Radius of Curvature nul/L 1/L, <br /> Maximum Curvature rad/L t/L <br />E Horizontal Strain (+) is Positive, (-) is Negative L2 <br />Em Maximum Horizontal Strain L2 <br />~ Angle of Draw Degrees <br />B Break An a De ees <br /> Angel ofMajor Influence Degrees <br />r Radius of Ma or Influence L <br />The focus of Exhibit 60B is on the South of Divide Mining Area. It is not feasible to quantify <br />subsidence by reference strictly to the Permit Revision Area; to the contrary, it is necessary to <br />• evaluate the relevant panels in their entirety. Exhibit 60 addresses subsidence in the Apache <br />Rocks and Box Canyon mining areas. Since mining activities are continuing in these areas, <br />1.05-94 RevisedJ~me 2005 PRIG <br />