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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 are mainly due to <br /> natural variations in the recharge rate. Water-level changes were observed in QR aquifer <br /> wells GD-2 and GF-6, along with associated backfill wells GD-3 and GF-11. Wells GD-2 and <br /> GF-6 are fairly close to mined areas but the 1999 gradual water-level decline observed in <br /> these four wells is mainly due to a decline in recharge. The increased recharge due to <br /> higher precipitation over the prior years had caused water-level increases and gradual <br /> water-level declines have occurred with the lower precipitation rates the last two years. <br /> These wells are located near the downgradient toes of D and E pits and/or at the interface <br /> of upgradient backfill and the downgradient native QR aquifer. These well locations seem <br /> -• to be relating to changes in precipitation with very little lag in time. <br /> Upgradient mining can cause water-level rises in wells downgradient of the mining <br /> by allowing ground water to flow to the downgradient end of mining quicker. Also, the <br /> backfill aquifers are generally more permeable than the native aquifer which also allows <br /> ground water to flow faster through the backfill material resulting in more water in the <br /> aquifer at this location. The input of additional water to the native aquifer at the north end <br /> (toe) of the mining has decreased the effects mine dewatering has had on water levels in <br /> this portion of the aquifer. Water levels in wells GD-2, GD-3, GF-6 and GF-11 are thought <br /> to be at or above the baseline levels for this reason. The slightly higher water levels in <br /> well GD-2 in 1998 than those observed in 1986 after six wet years indicates the post-mine <br /> levels under the same conditions may be higher. Springs are not expected to develop at <br /> • the north end of the D and F pits. <br /> 6-1 <br />