GENERAL45390

• Permit No: C1981025
• IBM Index Class Name: General Documents
• Doc Date: 7/8/1983
• Doc Name: Proposed Decision and Findings of Compliance
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

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However, given the present rate of mine inflows, the extensive area to be
undermined, and the steeply dipping strata within the area, there is only
a low potential for the North Thompson Creek No. 1 and No. 3 Mines to
discharge acidic or toxic waters to surface streams.
Ground water quality in overlying and underlying aquifers may become
degraded upon closure of the mine through vertical communication of
strata caused by faults and fractures. The overlying and underlying
aquifers are currently not put to beneficial use and the potential for
their future utilization is limited by the difficulty in developing water
wells in these strata. Owing to these factors, the mines will not
materially damage the ground water of any water user through vertical
migration of degraded mine waters.
The coal processing wastes from the wash plant are combustible and
acid-forming and potentially toxic. Owing to the nature of these coal
processing wastes, the applicant is presently constructing the coal
refuse pile to minimize exposure of wastes to air, surface water, and
ground water. The exposure to these wastes is being limited through
1) compacting the waste in two-foot lifts, 2) committing to cover the
refuse pile with four feet of non-toxic cover, 3) providing permanent
surface diversion of surface runoff from undisturbed areas around the
pile, 4) collecting and treating all surface drainage flowing over the
pile during construction and reclamation, and 5) benching and sloping the
pile such that erosion and infiltration of the final pile is minimized.
The refuse pile is being constructed on top of thin alluvium of the old
stream channel which will supply drainage of ground water beneath the
pile. The pile is being constructed over the relatively impermeable
Mancos Shale Formation and not over any aquifer. Therefore, the impacts
of the refuse pile on the quality of yround water should be minimized and
should not cause material damage to any yround water currently in use.
Waste water from the coal wash plant is currently recycled back into the
coal washing facility after fines have been settled out in upper and
lower settling ponds. This water recycling system tends to increase the
total dissolved solids in the water through exposure of the water to
fines and through evaporation. The ponds used in this water recycliny
system are unlined and are located on or are hydrologically adjacent to
the North Thompson Creek alluvium. Thus, these ponds pose a potential
for the degradation of the alluvial water quality directly and,
indirectly, the surface water quality of North Thompson Creek.
Alluvial monitoring well D-lA below the refuse pile has a water chemistry
markedly different from that in North Thompson Creek. The high levels of
both total dissolved solids, between 3498 and 3982 mg/l, and sulfates,
between 1900 and 2700 mg/1, indicate the refuse pile sediment pond and
unlined settling ponds may in part impacting the quality of alluvial