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-26- <br /> Faults and Fractures <br /> 17 <br /> Faults and fractures produce a localized increase in porosity within the <br /> strata cut by them. If the faults and fractures do not become sealed by <br /> clays, they may become conduits for the flow of ground and surface water. <br /> When encountered within the mine, faults and fractures will dewater. The <br /> amount of water flowing into the mine from these sources depends on porocity <br /> and permeability of faults or fractures, and on the open vertical connection <br /> within the faults and fractures between the coal seam and sources of ground <br /> or surface water. <br /> Fault and fracture controlled inflows have been noted and mapped in the U.S. <br /> Steel Corporation Somerset mine application (Exhibit E8-336) and the Western <br /> Slope Carbon Hawk's Nest mine permit application (Exhibit 2.04.7(1) or <br /> W-1006) . Colorado Westmoreland, Inc. has not mapped inflows to date. How- <br /> ever, they have noted inflows in faulted areas. No information is available <br /> on fault and fracture controlled inflows into the Bear mine and Blue Ribbon <br /> mine at present. The Mt. Gunnison No. 1 mine is presently under construction <br /> and has no data on mine inflows. <br /> Dewatering of Coal, Roof and Floor <br /> From information contained in their respective permit applications, water <br /> seeps from the coal, roof and floor upon advance of mining in the B and C <br /> seams of the Somerset mine, the D seam of the Orchard valley mine, and the E <br /> seam of the Hawk's Nest mine and Blue Ribbon mine. This source of mine inflows <br /> dries up one to two weeks after mining an area. The minor amount of water <br /> resulting from dewatering of the coal, roof and floor indicates that the <br /> coals and the overlying and underlying strata in the Mesa Verde Formation have <br /> very low permeabilities. Thus, these strata store and transmit very little <br /> water. Therefore, the impacts of dewatering the coals and the strata immed- <br /> iately above and below the coals within the Mesa Verde Formation will have an <br /> insignificant impact on the hydrologic balance. Also, the very slow rates of <br /> inflow resulting from dewatering strata indicate that these strata will not <br /> transmit significant quantities of water which will result in depletion of <br /> surface water sources. <br /> Subsidence <br /> The impacts of subsidence due to mining can be expected to vary in magnitude <br /> and extent. This variation will result from a combination of numerous <br /> natural phenomenon and from the effects induced by underground mining. Surface <br /> water and groundwater can both be influenced by differences in timing of <br /> mining and the physical environment. It is assumed that all- mining will <br /> result in subsidence at some future point in time, although surface manifes- <br /> tation may require many years to occur. Therefore, control and prediction of <br /> subsidence are critical, necessary measures to be implemented before and <br /> during any mining activity. <br /> Natural phenomena which influence subsidence are: <br /> - Depth of overburden <br /> - Thickness of the coal seam <br />