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• The units for the figures in the above table are; flow (gpm), pH (standard units); <br />conductivity (umhos/cm); total dissolved solids (mg/I) and iron (mg/I). Iron was measured <br />as total recoverable until April 1994 when the Colorado Department of Public Health and <br />Environment changed the discharge permit to require iron to be measured as potentially <br />dissolved. <br />Discharge from outfall 001 may slightly impact the quality of water in North Thompson <br />Creek. The mine water discharge has a low iron content and an acceptable pH, however <br />its conductivity is quite high. A 52 gpm flow with a conductivity of 2083 discharging into a <br />receiving stream with a 5 cfs flow and a conductivity of 494 (pre-permit mean) would <br />increase the conductivity of the receiving stream to about 530 umhos/cm, an increase of <br />less than 10% which is considered insignificant. <br />The Colorado Department of Health has implemented regulations regarding saline <br />discharges into the Colorado River. A discharge of one ton of salt per day can be <br />considered a no-salt discharge by the Department of Health. At the maximum expected <br />flow rate of 100 gpm from the No. 1 Mine, a TDS concentration of 1500 mg/I would yield <br />a salt concentration of 0.9 tons per day, slightly below the one ton per day of salt discharge <br />limitation. <br />Current monitoring requirements are presented on pages 3-61 and 3-86 of the permit. <br />Monitoring locations are presented in Volume V of the permit on Map D-4-23. Records of <br />• the above monitoring will be maintained and submitted to the Division annually in the form <br />of an annual hydrology report. Data will be reported on a calendar year basis. The annual <br />hydrology report will be submitted each year on or before March 30`" <br />L J <br />4-122 Revised April 2000 <br />