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• Field Measurements <br />North Thompson Creek <br />Snowmass has made monthly field measurements at both upstream and <br />downstream sites on North Thompson Creek since June 6, 1980, and has <br />collected water quality data since September 29, 1980. Field parame- <br />ters measured at both sites include electrical conductivity, pH and <br />water temperature. On June 26, 1981, flow monitoring was initiated. <br />All field measurements are listed in Appendix 3-P. <br />A seasonal pattern is evident for pH; which are at their highest level <br />(8.4) during peak runoff and are at their lowest (7.0) during <br />baseflow. A comparison of pH values at the upstream and downstream <br />shows little or no difference. There is no apparent impact from the <br />mine. <br />• Conductivity also shows seasonal patterns. The lowest value (113 <br />umhos/cm @ 25°C) occurred during peak flow and the highest value (1220 <br />umhos/cm @ 25°C) occurred during baseflow. Conductivity values are <br />consistently higher at the downstream site. The increase can be <br />explained by the changes in geology which causes an increase in total <br />dissolved solids (TDS) and the conductivity. This is further <br />discussed in Section 0..6.1.3 "Protection of the Hydrologic Balance". <br />Although there is an increase at the downstream site, conductivity is <br />still relatively low and a general indicator of good water quality. <br />Middle Thompson Creek <br />A monthly field monitoring program was initiated at two sites on <br />Middle Thompson Creek on June 11, 1981. Field measurements included <br />flow, conductivity, pH and water temperature, All field measurements <br />are listed in Appendix 4-G. <br />n <br />-_J <br />3-73 <br />