GENERAL34630

• Permit No: C1981025
• IBM Index Class Name: General Documents
• Doc Date: 7/28/2003
• Doc Name: Proposed Decision & Findings of Compliance For RN4
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

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