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Mountain Coal and Bear Coal Water Quality Assessment CO-0038776 and CO-0044377 Table A-3 In-stream Standards for Stream Se meat COGUNF06 -Physical and Biological ~ - ~ - Dissolved Ox en DO = 5 m /1, minimum H=6.5-9su Fecal Coliform = 325 colonies/100 ml .Inorganic- - Un-ionized ammonia acute =TVS Un-ionized ammonia chronic = 0.06 m 1 Chlorine acute = 0.019 m /1 Chlorine chronic = 0.011 m 1 Free C anide acute = 0.005 m I Sulfide chronic = 0.002 m I Boron chronic = 0.75 m Nitrite = 0.05 m 1 Nitrate = 10 m /1 Chloride chronic = 250 m I -Metals Total Recoverable Arsenic acute = 50 u 1 Dissolved Cadmium acute for trout and Dissolved Cadmium chronic =TVS Total Recoverable Trivalent Chromium acute = 50 u /1 Dissolved Hexavalent Chromium acute and chronic =TVS Dissolved Co er acute and chronic =TVS Total Recoverable Iron chronic = 1000 u 1 _ _ Dissolved Man anew acute and chronic =TVS Total Merc ~ chronic = 0.01 ua 1 Dissolved Nickel acute and chronic =TVS Dissolved Selenium acute =TVS Dissolved Selenium chronic = 10.6 u /1 throu h 12-31-06 Dissolved Silver acute and Dissolved Silver chronic for [rout =TVS Dissolved Zinc acute and chronic =TVS Hardness data for the various receiving streams near the point of discharge of the Mountain Coal ~1W. TFs and the Bear Ceal W WTFs were insufficient to conduct a regression analysis based en ±he low flow. Therefore, the WQCD's alternative approach to calculating hardness was used, which involves compuiing a mean hardness. The mean hardness for stream segment COGLTNF02 was computed to be 52 mg/1 based on sampling data provided by the permittee for the North Fork of the Gunnison River downstream of the West Elk Mine. Data from this location were available for a period of record from Apri12002 through September 2002. This hardness value and the formulas contained in the TVS were used to calculate the in-stream water quality standards for metals with the results shown in Table A-4. Appendix A Page 6 of 20 Last Revised 3/9/2004