2008-03-14_REPORT - C1981010 ‎(5)‎

• Permit No: C1981010
• IBM Index Class Name: REPORT
• Doc Date: 3/14/2008
• Doc Name: 2007 Annual Hydrology Report to Appendix A
• From: Trapper Mining Inc
• To: DRMS
• Annual Report Year: 2007
• Permit Index Doc Type: Hydrology Report
• Email Name: DIH
• Media Type: D
• Archive: No

Pyeatt alluvium. It had demonstrated the same seasonal variations (Figure A-11) as the alluvial P-1
well but has recently been dry.
Water-level elevations for the Johnson Gulch alluvial well J-1 are also presented in
Figure A-11. The J-1 water levels remained steady in 2007.
2.2 GROUND WATER LEVEL ELEVATION (PIEZOMETRIC MAP SIfMMARY)
Hydro-Engineering developed three piezometric maps to show the water level flow
patterns for the QR, HI and 3rd White Sandstone aquifers at Trapper Mine. Water levels from the
Fall of 2007 were used to develop these maps. The third quarter water levels were used because
two levels from the fourth quarter were questionable.
Map No. 2-1 presents the water-level elevations far the QR aquifer. The waxer-level
elevation is presented for the QR wells: GD-2, GF-6 and GP-5 and backfill wells GD-3 and GF-11.
The ground-water flow in the QR aquifer is mainly to the north. Mining has only affected the QR
aquifer close to the D, E, F, G and Z pits by causing drawdowns very near the pit edges. The
installation of backfill wells GD-3 and GF-11 has defined the depressed elevations in the backfill
areas. The wells in this area experienced a gradual water level rise during 2007. The water level
increases in 2007 are likely due to more recharge this last year. The backfill water levels will likely
stabilize lower than the pre-mine levels due to the increased permeability of the backfill aquifer,
which allows the water in the aquifer to be transmitted at a lower gradient. The gradient calculated
for the backfill near D pit is less than 0.05 ft/ft, compared to the undisturbed gradient of 0.12 ft/ft.
The heads in the northern end of the ba:ckfill aquifer will likely recover above the pre-mine level.
Backfill springs are not expected to develop near the northern end of the QR backfill because
backfill water levels would have to recover greater than a few tens of feet to reach the lower land
surface elevations. Table 2-1 of the 1990 Annual Hydrologic Report (Hydro-Engineering, 1991)
Trapper Mining Company 2'8
2007 Annual Report