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1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br />IL l <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br />MINREC, INC. ANNUAL HYDROLOGIC REPORT PAGE 5 <br />ANTICIPATED IMPACT <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 moderately high. The following table presents the impact outfall 001 <br />would have on the conductivity of North Thompson Creek at varying discharge rates. <br />Antici ated Im act -North Thom son Creek NTC - 2001 <br />Outfall 001 <br />Flow m Conductivity <br />Outfa11001 NTC Flow <br />cfs Conductivity <br />NTC Conductivity <br />Combined % Increase <br />Decrease <br />20 1884 5 494 506 2.5 <br />25.5 1884 5 494 510 3.2 <br />30 1884 5 494 512 3.7 <br />40 1884 5 494 518 4.9 <br />50 1884 5 494 524 6.1 <br />60 1884 5 494 530 7.3 <br />70 1884 5 494 536 8.5 <br /> <br />Conductivity -umhos/cm <br />The average flow during 2001 of 25.5 gpm with a conductivity of 1884 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 510 umhos/cm, an increase of <br />about 3.2% which is considered insignificant. <br />The Colorado Department of Health has regulations regarding saline discharges into the <br />Colorado River. A discharge of one ton of salt per day is considered a no-salt discharge <br />by the Department of Health. A flow rate of 100 gpm from with a TDS concentration of <br />1500 mg/I would yield a salt concentration of 0.9 tons per day, slightly below the one ton <br />per day of salt discharge limitation. The average flow rate at Outfall 001 was 25.5 gpm <br />with a TDS concentration of 1376 mg/I during 2001 which equates to a discharge of 0.21 <br />tons of salt per day. <br />The entire mine site has been reclaimed and seeded. Good plant growth has occurred <br />since 1988. During 1992 a study was performed at the mine site that demonstrates <br />untreated drainage from the reclaimed area contributes fewer suspended solids than <br />untreated drainage from the natural surrounding area, (permit pages 4-19i though 4-19iii). <br />None of the sediment ponds discharged during the year. <br /> <br />