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<br />and had a limited storage capacity (i.e., limited thickness and areal <br />extent). The water flowing from these fractures most likely <br />originated from overlying perched aquifers in lenticular sandstones <br />and from the fractures themselves. <br />The pulling of coal pillars within the mine may produce subsidence <br />at some point. The subsidence may impact the overlying <br />water-bearing strata with the Mesaverde formation. However, no <br />overlying strata are used for water supplies and no significant spring <br />flows to date have been observed emanating from these strata. The <br />potential future use of the lenticular sandstones for water supplies is <br />limited by: 1) the steepness ofthe stream valley slopes, 2) the depth <br />of drilling, 3) the low well yields which are expected from the tight, <br />fine-grained sandstones, and 4) the limited recharge areas of <br />lenticular sandstones. The Blue Ribbon Mine will not affect the <br />quality of water in the overlying strata. <br />The E coal seam is not an aquifer. The mine workings were dry, <br />except in a few areas of fracturing. <br />Impacts from Coal Mine Waste Disposal on Groundwater. During 1984 <br />and 1985, the mine bench at the Blue Ribbon Mine was stabilized by <br />rebuilding the mine bench with an engineered fill of underground coal <br />mine waste. This material was obtained from Mountain Coal <br />Company's West Elk Mine. Rock underdrains were placed in and under <br />the coal mine waste to channel spring water and seepage from the coal <br />mine waste fill. During 1986, it is estimated that the underdrains <br />discharged 1.37 acre-feet. In subsequent years, the flow has generally <br />decreased. During 1991, the underdrains discharged 0.035 acre-feet. <br />The conductivity of the discharge from the north underdrain has ranged <br />from 1,600 to 3,100 umhos/cm. The conductivity ofthe discharge from <br />the south underdrain has ranged from 3,300 to 5,300 umhos/cm. The <br />middle underdrain has never discharged. <br />The disposal of mine waste exposed fresh surfaces of saline shales and <br />sandstone for leaching by water infiltration from rainfall and snowmelt, <br />thus influencing the quality of subsurface flow. <br />The salt pickup rate depends heavily upon the local hydrology. A study <br />done by McWhorter and Rowe in 1976 suggests that total salt pickup <br />can be estimated from saturated spoil analyses and a knowledge of the <br />local hydrology of mine waste disposal area. This model would provide <br />a method of evaluating the impacts of mine waste disposal on water <br />quality. <br />The permeability contrast found in the pile will cause most of the <br />leachate water to perch within the refuse pile and above the native <br />soils. A shallow water mound will build within the pile and cause the <br />23 <br />