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likely recovered in the spoil spring discharges <br />Disturbed areas of the Oak Creek drainage have been, for the most part, reclaimed, and <br />sedimentation ponds have been removed. There is no post-mining condition that would deplete <br />runoff from these aeeas from pre-mining conditions. Flows in Oak Creek are not monitored. <br />An impact to surface water quality was anticipated in Trout Creek. The amount vas anticipated <br />to vary significantly, and is greatly dependent upon flows (seasonal and irrigatio~t calls) in Trout <br />Creek as vaziations in spoil spring flows are more moderated. TDS values were expected to rise <br />as high as 1,186 mg/1 at some time during the mining and postmining era at the E'sdna Mine (PAP, <br />page 2.SA-7). However, an annual average of 196 mg/1 is anticipated on page 4.fi-61(a) of the <br />PAP. The operator is asked to review this section of the PAP. <br />Sulfate concentrations were expected to reach an upper limit of approximately 842 mg/1(PAP <br />page 2.SB-3) in Trout Creek. Monitoring station TR-D is below mining activity on Trout Creek. <br />TDS values reported for TR-D ranged from 170 to 950 mg/1 during the 2004 water year. Sulfate <br />concentration ranged from 110 to 590 mg/1 at this surface water monitoring site. A summary <br />statement that all values for TDS in Trout Creek are consistent with the probable hydrologic <br />consequences projections is made on page 9 of the AHR. This review validates thhis statement, <br />and also finds that sulfate concentrations were within the anticipated range. <br />An impact to alluvial groundwater of Trout Creek was anticipated. TDS in alluvial materials was <br />expected to rise to 2000 - 3000 mg/1(PAP page 2.5-97). Alluvial groundwater i:~ monitored at <br />three stations, TR-1.5 above mining, TR-3 at the northern limit of mining (downstream), and TR- <br />4approximately amile below mining. TDS values in alluvial monitoring well TR-1.5 ranged <br />from 4210 to 4620 during the 2004 water yeaz. High TDS values in TR-1.5 have been noted for a <br />number of years, and they continue to rise. There is only speculation (in the PAP) for high and <br />rising TDS values in TR-1.5. TDS values in TR-3 ranged from 430 to 860 mg/1, and in TR-4 <br />from 460 to 960 mg/1. Impacts to alluvial groundwater of Trout Creek are within those predicted. <br />No impact to alluvial groundwater in Oak Creek was anticipated (PAP page 2.5-95b), and no <br />groundwater monitoring was conducted. <br />No probable hydrologic consequence was predicted in the PAP for bedrock groundwater. <br />Bedrock aquifers that abut spoil backfill probably are too impermeable to transmit any significant <br />amount of leachate. Those bedrock units in close proximity to the floor of the pit: are exposed (or <br />covered with a shallow mantle) below the pit and above Trout Creek. However, .a monitoring <br />station (an existing, privately-owned well) was established in the Trout Creek Sandstone (a unit <br />some 150 feet or more below the pit floor) directly downdip of mining activity. Pvlonitoring from <br />1995 indicates that TDS values have remained consistent in a range from 440 to 840 mg/1, with <br />no apparent rising trend. Monitoring at this station was not (due to equipment problems - no <br />power) accomplished during the 2004 water yeaz (brought to the attention of the operator). <br />CWQCCR 31 <br />Page 6 <br />