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SURFACE WATER MONITORING <br />• <br />Foidel Creek in the vicinity of Mine 3 is monitored for flow and <br />water quality, with USGS Site 09243900 (Site 900) located <br />approximately one-half mile upstream of the confluence of Foidel <br />and Middle Creeks. Flow and water quality are monitored at <br />locations on Middle Creek, with USGS Site 09243700 (Site 700) <br />located approximately one mile upstream of the confluence with <br />Foidel Creek, and Site 29 located approximately one mile downstream <br />of the confluence with Foidel Creek. <br />Flows <br />The streams are gauged at the two USGS sites and at Site 29. Due <br />to the size of the stream at the locations, they must be rated <br />instead of using a more accurate controlled section such as a <br />flume. The USGS maintains continuous recorders at Sites 700 and <br />900. Plots of the historic flow measurements on Foidel Creek are <br />presented on Figures 12 and 13. Plots of the historic flow <br />measurements on Middle Creek are presented on Figures 14 through <br />17. The flow rate data is summarized on Table 14. The data shows <br />the typical seasonal variation with a rapid rise and fall of flow <br />rates during spring runoff. Historically all three sites often do <br />not flow during the fall and winter. Due to the discharge effects <br />at other mines upstream of the gaging stations, Sites 900 and 29 <br />have normally flowed year-round since 1985. Nevertheless, as <br />depicted in Figures 12 through 15, spring runoff comprises most of <br />the annual flow. <br />Annual flows during the 1993 water year were higher than those <br />observed in recent years, but were well below the flows observed <br />during the wet years from 1984 through 1986. <br />Water Quality <br />Water quality samples are collected at all three monitoring sites. <br />The water quality summaries are presented on Tables 15 through 20. <br />Plots of historic water quality data for Foidel and Middle Creek <br />are presented on Figures 18 through 21. The historic base levels <br />of conductivity on Foidel Creek, measured during spring runoff, was <br />approximately 1000 umhos/cm. Since 1981 the base level has been <br />increasing and appear to have stabilized within the range of 1800 <br />to 2300 umhos/cm. This increase during the 1980's is due to the <br />effects of other mines upstream of Mine No. 3. Peak levels have <br />also increased during this period from levels around 1500 to 2000 <br />umhos/cm in 1975 through 1980 to levels exceeding 3000 umhos/cm in <br />1988-1993. The irrigation season level have approached 3000 <br />umhos/cm in recent years although slightly lower levels were <br />experienced in water year 1991 apparently due to the increased <br />flow. <br />• Page 6 <br />