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West Elk Mine <br /> <br /> <br /> <br />Table 60 <br />Wastewater Discharge Impacts on North Fork Gunnison River During Low Flow Conditions <br /> 7-Day, 10-Yr. <br />Low Flow 1-Day, 10-Yr. ~. <br />Low Flow <br /> Stream Flow CFS 32.5 25 <br /> Dilution Ratios <br />Effluent Discha a 10,000 d <br />2100 <br />1620 <br />Water Quali Parameter <br />BOD Effluent 30 30 <br />(mg/L) Incremental Change 0.014 0.018 <br />TSS EfFlUent 30 30 <br />(mg/L) Incremental Change 0.014 0.018 <br /> Background 137 137 <br />NH,-N Effluent 1 1 <br />(mom) Incremental Change .0001 .0001 <br /> Background .45 .45 <br /> Standard 0.905 0.905 <br />NO,-N Effluent 29 29 <br />(m9~-) Incremental Change 0.014 0.018 <br /> Background 0.20 0.20 <br /> Standard 10.0 10.0 <br />C1x Effluent 0.5 0.5 <br />(m9~) Incremental Change .0002 .0003 <br /> Standard .003 .003 <br />Feral Colifonn Effluent 6000 6000 <br />Colonies/100m1 Incremental Change 3 4 <br /> Background 18.8 18.8 <br /> Standard 2000 2000 <br />1 NPDES PermR Limd <br />2 Standard for total ammonia, derived from the mean annual pH value (7.8) and the maximum reported temperature value (66°F or <br />19°C value which results in an instream unionized ammonia concentration of 0.02 m 2 as N. <br />Following upgrades to the WWTP in 1997, the plant capacity increased to 20,000 gpd (0.02 <br />MGD) The maximum projected discharge rate from the WWTP is 0.04 MGD. This <br />projection is consistent with previously submitted projections with the exception of build-up <br />schedules. The build-up schedules aze estimates, which aze dependent on coal sales and mazket <br />conditions and may change accordingly. <br />Planning and expansion of the treatment plant will occur according to state (Colorado <br />Department of Public Health and Environment [CDPHE]) regulations. The level of projected <br />future maximum discharge (0.04 mgd) is still small compazed to the low flows in the North Fork, <br />and so should not significantly affect water quality of the river. In addition, effluent from the <br />WWTP goes through sedimentation pond MB-2R prior to discharge to the North Fork. <br />2.05-243 <br />Revised June 2005 PRIG; Rev. March 1006; Rev. May 1006 PRIG <br />