2012-02-27_REPORT - C1981025 - Laserfiche WebLink

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Anticipated Impact - North Thompson Creek NTC - 2011 Outfall 001 Flow gpm Conductivity Outfall 001 NTC Flow cfs Conductivity NTC Conductivity Combined % Increase (Decrease) 10 2202 5 494 502 1.5 15 2202 5 494 505 2.3 20 2202 5 494 509 3.1 25 2202 5 494 513 3.8 25 2202 5 494 513 3.8 30 2202 5 494 517 4.6 35 2202 5 494 520 5.3 40 2202 5 494 524 6.1 MINREC, INC. AHR ANTICIPATED IMPACT PAGE 4 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. Conductivity Outfall 001 - umhos /cm - Calculated for 2011 The average flow during 2011 of 25.0 gpm with a conductivity of 2202 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 513 umhos /cm, an increase of about 3.8% which is considered insignificant. The Colorado Department of Public Health and Environment has regulations regarding saline discharges into the Colorado River. A discharge of less than one ton of salt per day is considered a no -salt discharge by the Department of Health. A flow rate of 100 gpm from with a TDS concentration of 1500 mg /I would yield a salt concentration of 0.9 tons per day, slightly below the one ton per day of salt discharge limitation. The single TDS measurement for Outfall 001 1552 mg /I. A flow rate of 25 gpm would introduce 0.23 tons of salt per day into North Thompson Creek.