PERMFILE71827

• Permit No: C1981010
• IBM Index Class Name: Permit File
• Doc Date: 3/18/1991
• Doc Name: 1990 Annual Hydrologic Report
• Section_Exhibit Name: Appendix W 1990 Report Section 2.5
• Media Type: D
• Archive: No

The water levels in the three GE wells has become steady in
• 1990 which is thought to be due to the greater time since
dewatering stopped at the adjacent operation: It may also be
partly attributed to lower recharge rates and/or the mine
dewatering that started in the C pit in 1988.
Levels in the backfill areas are depressed and are likely not
to ever recover to pre-mine levels. Map 2-1 shows that the levels
in the backfill and downgradient aquifers are close. Well pairs
GD3-GD2 and GF11-GF6 present water levels that are very close in
water-level elevation for the backfill and downgradient QR aquifer
well. The mining is significantly increasing the permeability of
the mined aquifers which is a benefit relative to potential yields
from the aquifer. The increased permeability will likely not allow
water levels to recover to their pre-mine levels in the backfill
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will be above their pre-mine level. Water levels in the native
aquifer downgradient of the mining will likely stabilize above
their pre-mine levels.
The conductivity of water in backfill wells GD3, GF5 and GF11
are fairly similar to those in the native aquifers in these areas.
Conductivity of water from GF5 is probably 1.5 times the pre-mine
value. Conductivity in water from backfill well GF7 is much higher
than the naturally observed concentrations and will probably be
higher for several years before returtting to pre-mine
concentrations. Major constituent concentration in water in this
well are still increasing but seem to be .approaching their maximum
. levels. The water quality in QR wells GD2 and GF6 have not been
affected by the upgradient mining in this zone. The conductivity
6-2