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• o Modifications to hydrologic and subsidence monitoring plans <br />based upon observed trends to date <br />o Comprehensive updating and organization of permit materials <br />o Modification of the design post-mining topography to reduce <br />material handling requirements and enhance post-mining <br />drainage. <br />Except as specifically applicable, these changes do not significantly <br />effect EFCI's current operating methods and practices. The direction and <br />extent of future mining advance has been modified, however, current day- <br />to-day mining, processing, loadout and related operations will continue <br />without significant change. <br />As discussed in Section 2.04.6, Geology Description, the Southfield Mine <br />• is located in an area of gently sloping sedimentary deposits which are <br />overlain by colluvial/alluvial materials resulting from erosion and mass <br />wasting of the Pre-Cambrian Wet Mountain uplift to the west. The <br />sedimentary deposits have been tilted by the uplift and are truncated <br />along the southwestern margin of the permit area by the Wet Mountain <br />fault. Eleven known coal seams exist in this area although only three <br />(3), the Manley, Jack O'Lantern and Red Arrow seams have been identified <br />as being economically recoverable under current market conditions. <br />In order to provide a quality coal product which meets customer <br />specifications and applicable government regulations for sulfur dioxide <br />emissions, EFCI must blend production from the relatively high sulfur Red <br />Arrow seam with low sulfur production from the Jack O'Lantern seam. <br />Mining sequence, rate of advance and related production volumes are <br />governed primarily by these blending considerations. <br />EFCI currently mines the Jack O'Lantern and Red Arrow seams using room and <br />• pillar underground mining methods. Other economically minable seams occur <br />in this area, however most of these seams have been previously mined by <br />underground operations which occurred during the interval from 1935 <br />through 1955. <br />2.05-3 <br />