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- •j• x/81/1992 1: 27:O1PM H4DR0 307-266-6597 P2 <br />to the mining of this area. The water-level elevation at the <br />backfill aquifers are thought to be below pre-mine conditions, <br />except for close to the northern end of the mining. The <br />downgradient aquifers, in general, are thought to recover to above <br />pre-mine conditions due to the release of water upgredient vie the <br />higher transmitting ability of the backfill aquifers. The <br />permeability of the backfill at well GF-11 is approximately 7 times <br />the value downgradient in the native aquifer. <br />Response to D. 2. <br />The drier conditions comments should be referred to in <br />relation to the drier conditions for the past Few years relative to <br />the wetter conditions of the previous several years. The use of <br />the word "drought" may not be appropriate, where only 3 of the lest <br />Y years are below the average conditions. hells that were <br />initially constructed in the early 1980's rosy contain water levels <br />that are above the pre-mine conditions. This Factor needs to be <br />taken into account when trying to determine if mining has had an <br />impact on the water-level elevation of the aquifers. <br />Response to D. 3. <br />lJater-level elevations in alluvial well J-1 vary only a small <br />amount on a seasonal basis. It is very likely that the mining <br />upgredient of this alluvial system has released ground water from <br />upgredient and has increased the subsurface recharge to the <br />alluvial ground water system in this area. If this is the case, <br />then mining has substained the ground water levels in the Johnson <br />alluvial aquifer. The alluvial system in Flume Gulch has varied <br />much greater over the lest few years due to the wetter end drier <br />conditions and not so much due to seasonal conditions. IJater <br />levels have declined for the last several years in the Coy and GC-3 <br />wells, except for the 1991 water levels that did show an increase <br />in water level in upgredient well GC-3 but continued to gradually <br />decline in the Coy well. The recharge during 1991 must not have <br />been large enough to increase water levels in the Coy well but was <br />large enough to decrease the rate of decline in water levels in <br />this portion of the alluvium. <br />Response to D.S. <br />The Lewis Shale near well P-3 is hydrologically connected to <br />the Pyeatt alluvial ground water system. During the wetter years, <br />the Pyeatt alluvial system continually discharged to the stream <br />and, therefore, maintained a relatively constant water-level <br />elevation in the alluvial ground water system. Therefore, even <br />during the drier portion of the year, cater levels did not decline <br />very much in the alluvium during the mid-1980's. Since the surface <br />flow in the Pyeatt drainage has stopped for the last several years, <br />except for runoff events, alluvial and Lewis Shale water levels <br />fluctuate during the year due to the use of the alluvial ground <br />water. <br />Response to D. 6. <br />lJater levels in the GE series of wells rapidly declined in <br />1978. These water levels stayed low for several years, with water <br />levels rising at a fairly rapid rate in 1966 through 1988. Mining <br />in the Trapper Mine, A pit, started in May of 1977 and in July of <br />