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• A1INREC, 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 T hom son Creek NTC - 2000 <br />Outfall 001 <br />Flow m Conductivity <br />Outfa11001 NTC Flow <br />cfs Conductivity <br />NTC Conductivity <br />Combined % Increase <br />Decrease <br />30 1924 5 494 513 3.8 <br />40 1924 5 494 519 5.1 <br />50 1924 5 494 525 6.3 <br />60 1924 5 494 531 7.5 <br />70 1924 5 494 537 8.8 <br />80 1924 5 494 543 10.0 <br />90 1924 5 494 549 11.2 <br /> <br />• Conductivity -umhos/cm <br />A 40 gpm flow with a conductivity of 1924 discharging into a receiving stream with a 5 cfs <br />flow and a conductivity of 494 (pre-permit mean) would increase the conductivity of the <br />receiving stream to about 519 umhos/cm, an increase of about 5% which is considered <br />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. A flow rate of 100 gpm from <br />with a TDS concentration of 1500 mg/I would yield a salt concentration of 0.9 tons per day, <br />slightly below the one ton per day of salt discharge limitation. The average flow rate at <br />Outfall 001 was 36.8 gpm with a TDS concentration of 1329 mg/I during 2000 which <br />equates to a discharge of 0.29 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 that <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 />