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6.0 OBSERVED IMPACTS ON THE HYDROLOGIC SYSTEMS <br />OF THE TRAPPER MINE <br />6.1 GROUND WATER <br />Water -level changes in the last few years for the QR aquifer had been mainly due to natural <br />increases in the recharge rate but declined some in 2012 due to less recharge. Water -level changes <br />were observed in QR aquifer wells GD -2 and GF -6, along with associated backfill wells GD -3 and <br />GF -11. Water levels in wells GD -2 and GD -3 declined in 2006 and these declines are thought to be <br />due to some deep exploration drilling in this area. Water levels rose in 2008 and 2009, with some <br />additional rise in 2011 and 2012 in well GD -2. A gradual decline in water level in GD -3 was <br />observed in 2012. Additional monitoring with time is needed to determine the significance of the <br />decline in wells GD -2 and GD -3. Wells GD -2 and GF -6 are fairly close to mined areas, steady water <br />levels in 2012 were observed in well GF -6. The 2012 responses in well GF -11 indicated that water <br />levels declined due to the decrease in precipitation in 2012. These wells are located near the <br />downgradient toe of D and E pits and/or at the interface of upgradient backfill and the downgradient <br />native QR aquifer. These well locations seem to be relating to changes in precipitation with very <br />little lag in time. <br />Upgradient mining can cause water -level rises in wells downgradient of the mining by <br />allowing ground water to flow to the downgradient end of mine quicker. The backfill aquifers are <br />generally more permeable than the native aquifer which also allows ground water to flow faster <br />through the backfill material resulting in more water in the aquifer at this location. The input of <br />additional water to the native aquifer at the north end (toe) of the mine has decreased the effects <br />mine dewatering has had on water levels in this portion of the aquifer. Water levels in wells GF -6 <br />and GF -11 are thought to be at or above the baseline levels for this reason. The slightly higher water <br />levels in well GD -2 in 1998 than those observed in 1986 after six wet years indicates the post -mine <br />Trapper Mining Company 6 -1 <br />2012 Annual Report <br />