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

precipitation during this period. The water level in well GP-4 has also recovered to pre-mine levels
but observed variable levels in 2005 through 2007. The large decline in the fourth quarter should
not be given any significance until additional monitoring supports this value.
Well GMP-1 (Figure A-9) is completed in the HI aquifer to monitor ground-water
conditions downgradient of the ash disposal site immediately south in A pit. Water levels became
steady in 2001 and stayed fairly steady the last six years with a small increase in 2006 and 2007.
Figure A-10 atso presents water levels for the well COY (alluvium). Water levels at the
COY well overall rose in 2007 likely due to an increase in recharge. The unconfined alluvial
aquifer generally responds gradually to recharge changes. The 2007 water-level elevations are
similar to the natural high water levels in 1985 and 1986.
Well GP-5 is completed in the QR aquifer. GP-5 is immediately downgradient of A pit.
Water-level data. is tabulated in Table A-1 in Appendix A. Figure A-11 presents the water level
versus time plot, showing a rising trend for the last two years during the period of above normal
precipitation which was preceded by fairly steady levels during the below normal precipitation
period. These responses are interpreted to be due to a decrease in recharge followed by an increase
in recharge during the Last three years. These water levels show no response to the higher
precipitation in 2005 while a good response in shown to the higher 2006 and 2007 precipitation.
This data indicates a one yeaz lag in the water level responses in well GP-5 to precipitation. These
responses indicate that the mining from the QR seams, which is nearest in the F pit mining that
began in 1997, has not significantly affected water levels in well GP-S.
Figure A-11 presents the change in water-level elevation for alluvial well P-l, located in
the Pyeatt drainage north of the PA. This data demonstrates classic seasonal responses, highs in
winterJspring and lows in late summerffall. Overall the water levels were similaz in 2007 with a
gradual decline. Well P-3 is completed in the Lewis Shale outcrop, which is in contact with the
Trapper Mining Company 2-7
2007 Annual Report