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2. The proposed mining operations would not cause material damage to the quantity and <br />quality of surface and ground water that supply the alluvial valley floors. The affected azea <br />of proposed PR-07 does not underlie any AVF (see Map 15 of the approved PAP and map <br />23B of the PR-07 application). <br />The only significant degradation of stream water from TCC's mining operations has been <br />caused by pumping of underground mine water into Fish Creek and Foidel Creek. Data in <br />TCC's annual hydrology reports document this degradation. Pumping occurs at two sites, <br />115 (Fish Creek borehole) and 109 (portal azea). The pumping loads the streams with <br />dissolved solids, mainly sulfate. The operator has maintained stream water quality below the <br />material damage threshold by limiting the pumping rates at both sites and treating the <br />pumped water at one of the sites, 115. The operator proposes no change in PR-07. The <br />operator would continue to limit pumping rates and treating water as in the past; therefore, <br />mine pumping can be expected to not cause material damage to the quality of surface water <br />or alluvial water. <br />Water in Fish Creek could see a slight increase in sediment load as subsidence slightly <br />changes the stream channel gradient and minor erosion occurs at head cuts in the stream <br />channel for areas previously approved. This increase in sediment load should be no more <br />than what is observed during high spring runoff and after lazge rainstorms. An increased <br />sediment load was not detected during past subsidence of Fish, Foidel, and Middle Creeks. <br />No impact to groundwater quality is predicted. Ground water could flow between aquifers <br />through subsidence fractures. The Fish Creek alluvium and the Twentymile sandstone have <br />the greatest potential for such interstratal flow, but the stratigraphic sepazation of several <br />hundred feet between the two units would prevent any significant amount of flow between <br />them. <br />Water quality impacts to the stream alluvial aquifer system of Fish Creek could result from <br />two additional processes: mine water discharge through boreholes/shafrs during mining and <br />contamination of tributary ground water through seepage from the underground workings <br />after mining has ceased and the workings have flooded. Impacts from mine water dischazge <br />during operation will be discussed first. <br />Originally, mine water dischazge was projected to have an electrical conductivity of 1 <br />mmhos/cm at a projected dischazge rate of 0.41 cfs. Actual data from numerous years of <br />operation reveals mine water discharge values of approximately 0.20 cfs but an electrical <br />conductivity of neazly 3 mmhos/cm. Dischazge and conductivity in this range would cause a <br />measurable increase in salinity downstream on Fish Creek. Stream flow modeling conducted <br />during the CHIA produced EC values in the area of .750 mmhos/cm, given a conservative <br />TDS/EC ratio of .8, for areas downstream of the Fish Creek dewatering borehole. Electrical <br />conductivity values at this level would not materially damage crop production from either <br />flood irrigation or sub-imgation. <br />As was the case on Trout Creek, the majority of the plant species identified in surveys <br />conducted by the applicant and summarized in the supplemental package of September 22, <br />33 <br />