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Nickel (Ni) <br />There has been no continuous or recent monitoring for nickel at the downstream <br />monitoring location on North Thompson Creek, thus there is no direct information to <br />determine the relationship of downstream concentrations of nickel with the Numeric <br />Standazd. The Numeric Standazd for nickel is 83 ug/1(chronic). Nickel was undetected in <br />Outfa11001 dischazges of July 17, 2001. <br />Selenium (Se) <br />There has been no continuous or recent monitoring for selenium at the downstream <br />monitoring location on North Thompson Creek, thus there is no duect information to <br />determine the relationship of current downstream concentrations of selenium with the <br />Numeric Standard. The Numeric Standard for selenium is 4.6 ug/1(chronic). Selenium <br />was undetected in upstream baseline monitoring, ranged from undetected to 6 ug/l in <br />baseline downstream samples, and was undetected in the Outfall dischazge of July 17, <br />2001. <br />Silver (Ag) <br />Silver was undetected in the 7uly 17, 2001 sample of Outfa11001 discharge. There has <br />been no other testing for silver. The Numeric Standazd for silver is 0.84 ug/1(chronic). <br />Zinc (Zn) <br />Monitoring results indicate that zinc concentrations in North Thompson Creek are not <br />effected by Outfall 001 discharges, and that the Numeric Standazd for zinc is not <br />exceeded in downstream flows. The Numeric Standazd for zinc is 190 ug/1(chronic). <br />Other Effects <br />Conductivity <br />There is no conductivity receiving stream standazd. However, the Division has <br />established a material damage suspect level for irrigation water in northwest Colorado of <br />1,500 umhos/cm. The suspect level of 1,500 umhos/cm is based on technical Titerature <br />that indicates irrigation water of this salinity could reduce a farm's crop yield by at least <br />3%. Monitoring suggests that there may be an increase in the conductivity of North <br />Thompson Creek from Outfa11001 dischazges, but that it is not significant. The <br />September 8, 2002 conductivity of Outfa11001 was 1,890. The upstream conductivity was <br />160 and the downstream 180. The average (1995 - 2002) conductivity of North <br />Thompson Creek was 494 µmho/cm downstream of the mine portals and 216 µuiho(cm <br />upstream of the mine portals. <br />28 <br />