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<br />MINREC, INC. Page 3 <br />' NORTH THOMPSON CREEK MINES <br />1991 AHR <br />' MINE WATER QUALITY <br />The quality of the No. 3 Mine discharge is measured monthly. <br />' Prior ,years monitoring of this discharge has been summarized into <br />a monthly format and is included in Appendix IV. The quality of <br />the discharge from the mine shows little change from previous <br />' years. <br />The quality of the No. 1 Mine discharge is presented in a <br />' table in Appendix IV. The quality of the discharge from the mine <br />shows little change from prior years except that since chemical <br />treatment is no longer necessary, the conductivity and total dis- <br />solved solids of the mine discharge water have decreased about <br />' 20Y. <br />ANTICIPATED IMPACT <br />Discharge from the No. 1 mine continues to slightly impact <br />the quality of water in North Thompson Creek. The mine water <br />' discharge has a low iron content and an acceptable pH, however <br />its conductivity is quite high. A 30 gpm flow with a conduc- <br />tivity of 3000 discharging into a receiving stream with a 5 efs <br />' flow and a conductivity of 150 would increase the conductivity of <br />the receiving stream to about 188 which is considered insig- <br />nificant. <br />' The Colorado Department of health is implementing nesa <br />regulations regarding saline discharges into the Colorado River. <br />A discharge of one ton of salt per day can be considered a no- <br />' salt discharge by the Department of Health. At the maximum ex- <br />pected flow rate of 40 gpm from the No. 1 Mine, the TDS con- <br />centration could be as high as 4150 mg/1 and still not exceed the <br />' one ton per day of salt discharge limitation. Currently the TDS <br />of the discharge is consistently about 2000 mg/1. <br />The entire mine site has been reclaimed and seeded. Good <br />' plant growth occurred during 1988, 1989, 1990 and 1991. As <br /> vegetation is established, the potential for drainage from the <br /> disturbed area to contribute additional suspended solids into <br />' North Thompson Creek is reduced. <br />t <br />1 <br /> <br />