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• All exploration drillholes completed by EFCI within the Southfield permit <br />area are either completed as monitoring wells or sealed following <br />completion of drilling, sampling and logging. Well completion and sealing <br />methods are described in Sections 2.02, Coal Exploration, 2.05.4, <br />Reclamation Plan, and 4.07, Sealing of Drilled Holes and Underground <br />Openings. <br />EFCI's planned underground mining operations will result in some <br />groundwater inflows both from the stratigraphic units disturbed by mining <br />and from abandoned underground mine workings where the separation interval <br />is minimal allowing subsidence fracturing to provide an effective <br />hydrologic connection. As mining proceeds, these groundwater inflows will <br />result in a localized reduction in the piezometric surface. A localized <br />cone of depression will develop, with continued groundwater inflows until <br />some point in time after mining operations cease, the mine workings fill <br />with water, and the piezometric surface stabilizes. <br />• Underground mining operations will expose coal, floor, and roof materials <br />to oxidation and increased leaching as mining is completed and active <br />working areas are abandoned. Natural caving will result in substantial <br />quantities of broken coal and roof material which will also be exposed to <br />oxidation and leaching as these areas flood from continuous mine seepage. <br />It is anticipated that increased groundwater contact with these oxidized <br />materials will result in a shift in groundwater chemistry toward a sodium <br />sulfate water type, and increases in pH and the concentration of TDS and <br />certain mineral constituents including iron and manganese. <br />Mitigation of these potential impacts of the underground mining operations <br />will be limited .to development and disturbance of the minimum area <br />necessary to provide for effective coal extraction as previously noted in <br />Section 2.05.3, Operations Plan - Permit Area. EFCI, to the extent <br />operationally practical, keeps all development except ramping and <br />overcasts in the minable coal seams. Further, the dimensions of mine <br />. openings are constrained both by the thickness of the minable coal seams <br />and by practical ground control considerations. While there will <br />undoubtedly be some impacts on groundwater quality, these impacts will <br />2.05.6-22 <br />