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Subsidence fractures that develop over mine workings have the potential <br /> to dewater natural springs and wetlands in the West Elk permit area. The <br /> permit application explains that the risk of such depletion is significantly <br /> reduced by the overburden thickness of greater than 280 ft. and the <br /> resistance to fracturing of interbedded fine-grained units that would <br /> deform ductiley(bending), rather than brittley (fracturing). Monitoring <br /> of springs since before the mine was developed has not detected impacts <br /> from mining. This monitoring will continue. <br /> The operator predicts overall ground water/surface water balance will not <br /> be significantly affected if mine inflows are much greater than predicted <br /> because mine inflows will ultimately be discharged back to the North <br /> Fork of the Gunnison. <br /> i. Refuse Material Disposal Impacts on Groundwater - <br /> Lower Refuse Disposal Area—Coal mine waste will be disposed <br /> in the Lower Refuse Disposal and Refuse Pile Expansion sites. <br /> The lower refuse pile is permitted for permanent disposal of 1.09 <br /> million cubic yards of mine development waste and sediment <br /> pond cleanout material. The refuse pile expansion is designed to <br /> hold 1.38 million tons of material over a life of 9.4 years. The <br /> Refuse Pile Expansion is discussed in Permit volume IOB. An <br /> Upper Refuse Disposal Area has also been approved for <br /> construction, and has not been built. MCC has verbally indicated <br /> this pile will not be needed. Stipulation#7 requires MCC to <br /> complete a geotechnical investigation prior to constructing Upper <br /> Refuse Pile. <br /> To date, refuse piles have not impacted the groundwater zone <br /> near Sylvester Gulch. Because of the low permeability of the <br /> colluvial soils and the lack of a groundwater table near the <br /> surface in the colluvium, no impacts on groundwater are <br /> anticipated. Water monitoring near the site of the soil stockpiles <br /> and waste piles, other water quality monitoring stations on <br /> Sylvester Gulch, and sites above and below the mine on the North <br /> Fork of the Gunnison, provide data on impacts of this refuse <br /> stockpile. The wells in the colluvium in the vicinity of the refuse <br /> piles have been mostly dry since 2000 or yielded insufficient <br /> water to provide an analysis. <br /> A leachate study of the F-seam refuse was conducted and <br /> included in the application for the permanent refuse disposal site <br /> in Exhibit 51 of the permit application. In addition, the effects of <br /> B-seam refuse on leachate were also evaluated and can be found <br /> in Exhibit 56. The permeability contrast found in the pile will <br /> cause most of the leachate to perch within the refuse pile and <br /> above the native soils. A shallow water mound will probably <br /> 44 <br />