REP00595 - Laserfiche WebLink

Home Browse Search

. MINREC, INC. ANNUAL HYDROLOGIC REPORT PAGE 5 ANTICIPATED IMPACT Discharge from outfall 001 may slightly impact the quality of water in North Thompson Creek. The mine water discharge has a low iron content and an acceptable pH, however its conductivity is moderately high. The following table presents the impact outfall 001 would have on the conductivity of North Thompson Creek at varying discharge rates. Antici ated Im act -North T hom son Creek NTC - 1999 Outfall 001 Flow m Conductivity Outfa11001 NTC Flow cfs Conductivity NTC Conductivity Combined % Increase Decrease 30 1613 5 494 509 3.0 40 1613 5 494 514 4.0 50 1613 5 494 518 4.9 60 1613 5 494 523 5.9 70 1613 5 494 528 6.8 80 1613 5 494 533 7.8 90 1613 5 494 537 8.7 Conductivity - umhos/cm A 40 gpm flow with a conductivity of 1613 discharging into a receiving stream with a 5 cfs flow and a conductivity of 494 (pre-permit mean) would increase the conductivity of the receiving stream to about 514 umhoslcm, an increase of about 4% which is considered insignificant. The Colorado Department of Health has implemented regulations regarding saline discharges into the Colorado River. A discharge of one ton of salt per day can be considered a no-salt discharge by the Department of Health. A flow rate of 100 gpm from with a TDS concentration of 1500 mg/1 would yield a salt concentration of 0.9 tons per day, slightly below the one ton per day of salt discharge limitation. The average flow rate for the No. 1 Mine was 42.1 gpm with a TDS concentration of 1408 mg/I during 1999. The entire mine site has been reclaimed and seeded. Good plant growth occurred during 1988 through 1999. During 1992 a study was performed at the mine site that demonstrates that untreated drainage from the reclaimed area contributes fewer suspended solids than untreated drainage from the natural surrounding area, (permit pages 4-19i though 4-19iii). None of the sediment ponds discharged during the year.