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will be reestablished sooner than would otherwise have been the case. <br />Subsidence effects include fracturing of the material overlying the coal for a <br />distance of 30 to 40 feet due to caving of the roof material and surface subsidence <br />and possible development of tension cracks on the surface due to differential <br />settling. Observed ground water inflows during mining have been approximately <br />50 gpm. In fractured azeas, increased flows of 100 to 300 gpm may be <br />encountered for a short period of time. These flows will diminish as equilibrium <br />is reestablished. Due to the low transmissivities of the aquifers, if caving should <br />create a hydraulic connection from the mine to an aquifer within 30 to 40 feet of <br />the coal, the additional inflow will be minimal. It is not probable that fracturing <br />from the mine to the surface will occur as a result of subsidence and cause the <br />flow of surface water to the mine. <br />Subsequent to completion of mining, the ground water will slowly reestablish its <br />pre-mining water levels. Due to the caving of the roof materials into the mine, an <br />azea of increased permeability will exist within the mine that will act as a "sump <br />area" until equilibrium is established. However, due to the small quantity of <br />water in the aquifers being dischazged to the White River and its tributaries, the <br />lack of ground water usage in the azea, and the poor quality of ground water, <br />potential impacts to flow in the White River will be very minor. <br />It could be possible for water to dischazge from the portals once the mine <br />workings have become completely flooded. The portals aze updip in the mine <br />and drainage will tend to move down the dip of the mine and coal seam, thereby <br />increasing the time to flood the workings; however, it is uncertain if the drainage <br />out of the mine area through the coal seam will exceed the drainage into the mine <br />from overlying strata. If outflow does not exceed inflow, some dischazge from <br />the portals may occur. The permittee has proposed backfilling of the portals and <br />construction of bulkheads upon closure of the mine, minimizing the possibility <br />for dischazge of water. <br />In the northern sections of the mine plan azea is a lazge coal refuse disposal azea. <br />Drill hole data indicate that there is no ground water within 44 feet of the ground <br />surface in the disposal azea, and rechazge to ground water in the Mesaverde <br />Group is minimal. Infiltration of water through the refuse pile will be minimized <br />by covering the compacted refuse with 30 to 48 inches of the best available non- <br />toxic material. Impacts to the ground water system aze not expected to be <br />significant due to the relatively impermeable nature of the refuse and the low <br />water table. <br />The development and reclamation of the cuts and fills in the portal areas should <br />have no impact on the bedrock aquifer system. Recharge of the aquifers does not <br />occur in these areas due to surface water control systems, so possible degradation <br />of the ground water by infltrating waters is unlikely. The fill material itself is <br />_ _ generally of suitable quality as a topsoil substitute except for SAR values which - - <br />34 <br />