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<br /> <br /> <br /> <br /> 16 <br />be released from the mine portals. Recharge of deep aquifers into the Piceance <br />Creek structural basin might be diminished (due to loss of hydraulic head <br />above the mines), but pooled mine water becomes a source of recharge to all <br />hydraulically-connected seams of lower piezeometric levels. Such is not likely at <br />the North Thompson Creek Mines. Piezeometric surfaces of ground water about <br />the mined areas are higher than the mine portals. There is likely little, if any, <br />recharge into these aquifers from the flooded mines. If there is any, such water <br />would be carried to great depths and undoubtedly becomes quite high in dissolved <br />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 TR-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.