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Revised 11/85 <br />• Subsidence Information <br />Subsidence Effect on Renewable Resources. The effect of surface <br />subsidence on renewable resources will be minimal. Maximum surface <br />subsidence will be six (6) feet or less depending on the thickness of <br />coal extracted below a given area. Subsidence will be area type <br />subsidence rather than chimney or sink hole type subsidence. Subsidence <br />will occur in two (2) phases. <br />The effect of surface subsidence on renewable resources will be minimal. <br />Maximum surface subsidence will be six (6) feet or less depending on the <br />thickness of coal extracted below a given area. Subsidence will be area <br />type subsidence rather than chimney or sink hole type subsidence. <br />Subsidence may occur in two (2) phases. <br />The first subsidence phase may occur shortly after mining under an area. <br />Settling, if any, will occur after the pillar retreat line passes <br />• through an area. This dynamic phase will be transitory. Surface cracks <br />will appear and a noticeable difference in surface elevation will be <br />evident. The magnitude of surface cracking will be dependent on the <br />depth of overburden in an area. Cracking will be greatest in areas of <br />less overburden. Given the relatively high cover above the Bear Coal <br />Company operations, settling will be minimal. <br />The second phase will begin when mining is completed in an area. The <br />surface will slowly establish an equilibrium condition. Subsidence <br />will extend beyond the mining limit and equalize over the area. <br />It is not possible to precisely predict the maximum lateral extent of <br />subsidence. For steeply dipping coal seams (15° to 35°), the angle of <br />draw has been measured to be as much as 45°. For flat coal seams, the <br />angle of draw has been measured to be 20°. It is assumed that 45° is <br />the maximum lateral extent of subsidence but it is not anticipated that <br />• this will occur. The Geology/Hydrology Map (Map 6) shows the <br />anticipated extent of subsidence, utilizing the angle of draw of <br />approximately 25°. Subsidence will be very slight at the maximum extent <br />and increase toward the center of the mined area. <br />_pp_ <br />