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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 aqu'der <br />wells GD-2 and GF6, along with assodabed badcfill wells Go-3 and GF-11. Wells GD-2 and <br />GF-6 are fairly close to mined areas but the steady to gradual rise in water levels observed <br />in these four wells in 2tm3 are mainy due to variation in recharge. The responses in these <br />wells indicated that the present water level will be maintained with precip'~tation that is <br />slightly below normal. These wells are located near the downgradient Goes of D and E pits <br />and/or at the interface of upgradient backfill and the downgradient native QR aquifer. <br />These well locations seem ib be relating to changes in predpibtion with very lithe lag in <br />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. The baddll <br />aquifers are generaly more permeable than the native aquifer- which also allows ground <br />water to flow faster through the bac~ll material resulting in more water in the aquifer at <br />this location. The input of additional water to the native aquifer at the north end (toe) of <br />the mining has decreased the effects mine dewatering has had on water levels in this <br />portion of the aquifer. Water levels in wells GD-2, GD-3, GF6 and GF-11 are thought to be <br />at or above the baseline levels fur this reason. The slightly higher water levels in well Gt}2 <br />in 1998 than those observed in 1986 after six wet years indicates the post-mine levels under <br />the same conditions may be higher. Springs are not expected to develop at the north end <br />of the D and F pits. <br />6-1 <br />