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solids. This water would probably be unfit for most domestic and agricultural <br />uses. Drilling of wells to these depths would be uneconomical. There are no <br />known registered (State Engineer's Office) wells in the mine permit area. <br />Owing to these factors, the mines are not materially damaging the ground water of <br />any water user through vertical migration of degraded mine waters, or diminished <br />recharge. <br /> <br />The coal processing wastes from the wash plant are combustible, acid- <br />forming, and potentially toxic. These processing wastes, along with coal mine <br />waste, were placed in a coal refuse pile. This pile was constructed to minimize <br />exposure of wastes to air, surface water, and ground water through (1) compaction <br />of the waste in two-foot lifts, (2) coverage of the refuse pile with non-toxic cover, <br />(3) provision of permanent surface diversion of surface runoff from undisturbed <br />areas around the pile, and (4) benching and sloping the pile such that erosion and <br />infiltration of the final pile is minimized. It was constructed over the relatively <br />impermeable Mancos Shale Formation and not over any aquifer or ground water <br />flow path. With the above construction procedures, the effects of the refuse pile on <br />the quality of ground water should be minimized and should not cause material <br />damage to any ground water currently in use. A sedimentation pond was <br />constructed at the toe of the mine waste pile. The intention of this pond was to <br />perform as a sedimentation pond for surface runoff from the waste pile area, and to <br />collect any spoil spring discharge that might develop. This pond is now permitted <br />for retention as a stock pond, and may collect runoff from the watershed above or <br />be filled by discharge from the mine water treatment system upstream. The refuse <br />pile pond was constructed on top of thin alluvium of the old stream channel. <br />This would likely result in drainage of ground water beneath the embankment. <br />Piezometers were installed in geotechnical investigation holes above, under, <br />below, and upstream of the proposed refuse pile. Piezometer D-lA, placed <br />below, and piezometer D-2A, placed upstream, were reclaimed with the approval <br />of Technical Revision 23 on February 23, 2004. <br /> <br />The water in these two alluvial monitoring wells has water chemistry different <br />from that in North Thompson Creek. Monitoring suggests that there may be <br />some degradation of water quality in the alluvial materials between the mine <br />waste pile and North Thompson Creek from leaching of waste materials. <br />However, it may not be significant as surrounding groundwater has relatively <br />higher conductivity. <br /> <br />During mining operations, waste water from the coal wash plant was recycled back <br />into a coal washing facility after fines settled out in upper and lower settling <br />ponds. This water recycling system increased the total dissolved solids in the <br />water through exposure of the water to fines and through evaporation. The ponds <br />that were used in this water recycling system were unlined and were located on, <br />or were hydrologically adjacent to, the North Thompson Creek alluvium. Thus, <br />these ponds posed a potential for the degradation of the alluvial water quality, and <br />may still be reflected in the higher conductivity of samples from piezometer D- <br />2A. Mining has ceased, the washing facilities have been removed, and the <br /> <br /> <br />15 <br /> <br />