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West Elk Mine <br />. The purpose of this section is to describe, on a site specific basis, and to quantify, to the extent <br />feasible, the various phenomena that are embodied in this definition. This section provides an <br />inventory of structures and renewable resource lands in the current permit area, which includes the <br />Box Canyon pemut revision area, as well as a subsidence survey analysis, potential subsidence <br />consequences, and the subsidence monitoring and control plan. Table 42 of this section provides a <br />list of symbols and definitions for commonly used terms associated with subsidence and used <br />frequently in this section. <br />Table 42 Definition of Subsidence Terms <br />• <br />• <br />S mbol Defmition Dimensions <br />S Vertical Dis lacement Subsidence) L <br />Sm Maximum Vertical Dis lacement Sm a•t L <br />S/Sa, Ratio of Vertical Displacement to Maximum <br />Vertical Dis lacement L2 <br />Sh Horizontal Dis lacement L <br />t Coal Extraction Thickness L <br />a= Sm/t Subsidence Factor L2 <br /> Subsidence Factor above Chain Pillazs L/L <br />S =a~ •t Maximum Subsidence Above Chain Pillars L <br />d Overburden De th L <br />Sm/d Ratio of maximum vertical displacement'to <br />overburden de th L2 <br />War Critical Extraction Width L/L <br />W/d Mining Width to Overburden De th Ratiq L/L <br />M Tilt Slo e) L/L <br />Mm Maximum Tilt L/I, <br />C Curvature, the reciprocal of Radius of <br />Curvature rad/L (1/L) <br />Cm Maximum Curvature rad/L (12) <br />E Horizontal Strain (+) is Positive, (-) is <br />Ne ative L/L <br />Em Maximum Horizontal Strain L/L <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 />It is essential to understand the distinction between the "Apache Rocks permit revision area", the <br />"Apache Rocks mining area" and the "Box Canyon Pemut Revision Area" and to be aware of the <br />terminology regarding the panels in various azeas. Consequently, the following definitions and Map <br />lA (and Map 1 in Exhibits 60 and 60C) have been prepared. <br />2.05-98 RevisedJw. 1995 PR06;1/96 RN03; Revised May 1999 TR89;RevisedJan./998 PR08;RevisedJan. 1999 PR08;March 2005PR/1 ~~ol <br />.~ <br />'~'J <br />