GENERAL52614

• Permit No: C1981044
• IBM Index Class Name: General Documents
• Doc Date: 4/24/1987
• Doc Name: Proposed Decision & Findings of Compliance for PR1
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

mentioned, this longwalling will undoubtedly result in some surface subsidence
and there might be fracturing of the overburden which could promote discharge
of overlying aquifers into the mines. This fracturing might even extend
upward to the level of the Twentymile sandstone. The area being longwalled in
the No. 5 and No. 6 Mines during the first five years, however, lies near the
southern outcrop pf the Twentymile sandstone where the aquifer is relatively
unsaturated or has little head. Given this fact and the stratigraphic
separation of the aquifer from the mining level, no significant impact on the
quantity of water in the Twentymile sandstone should occur. The applicant
estimated that under "worst case conditions" a water level decline of 60'
might occur in the Lux well, reportedly completed in the Twentymile sandstone
approximately one mile from the area of surface subsidence. Although the
chemical quality of the water furnished by the Lux well is not incompatible
with that sampled elsewhere in the area from the Twentymile sandstone, it is
not considered likely that the Lux well with its location and reported depth,
actually reaches the level of the Twentymile aquifer.
The White sandstone lies approximately 500' above the Twentymile sandstone and
that much more removed from the effects of Eagle No. 5 and No. 6 mining.
Little of the current extent of the No. 5 Mine underlies the White sandstone;
none of the proposed future operations is the No. 5 Mine will do so. The area
of the No. 6 Mine is not predicted to reach below the White sandstone until
after the first five years. Since no impact of the Eagle No. 5 mining on the
quantity of water in the White sandstone has been demonstrated in the past,
none is forecast for the future. No water supply wells are currently
completed in the White sandstone in the permit or adjacent areas.
Proposed future operations in the Empire No. 5 and No. 6 Mines are not
projected under the Yampa River alluvium during the first five year permit
term. Portions of the existing No. 5 Mine, however, already extend under the
Yampa River alluvium in the area downstream from the confluence of the Yampa
River with the Williams Fork River. There is infl ow into the underlying No. 5
Mine in this area, both from general sources as well as from known fault
zones. There should, however, be no impact on the quantity of water in the
Yampa River alluvium from this inflow. While there is no present monitoring
of the water levels in the Yampa River alluvium to demonstrate this, there has
been no impact of this inflow on the quantity of water in the White and
Twentymile sandstones which have been monitored and which lie between the
level of the No. 5 mining artd the alluvium. Furthermore, whatever the source
of the mine inflow, this water is returned to the local surface
stream/alluvial systems from the mine by way of the permitted discharge into
the Williams Fork River.
The Eagle No. 5 Mine also presently extends under the Williams Fork River and
associated alluvium. Portions of the No. 6 141ne will underlie the Williams
Fork River and alluvium in this same area. Yery little seepage is now
reported to occur in the No. 5 Mine workings in this part of the operation.
As a result, very little from an alluvial source is expected in the No. 6 Mine
which will be situated directly below the No. 5. Water levels in the Williams
Fork alluvium, while showing seasonal variations in the permit area, have
actually demonstrated a tendency to rise over the long term.
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