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Trapper Mining, Inc. W WTF Water Quality Assessment CO-0032115 <br />Table A-2 <br />In-stream Standards for Stream Se went 36: COLCLY03b <br />Ph sica( and Blolo 'caf <br />Dissolved Ox en DO = 5 m minimum <br />H=6.5-9su <br />Fecal Coliform = 325 colonies/100 ml <br />Inorganic <br />Free C nide acute = 0.2 m <br />Boron chronic = 5 m <br />Nitrite = 10 m <br />Nitrate =100 m 1 <br />Metals <br />Total Recoverable Arsenic chronic = 200 u 1 <br />Total Recoverable Cadmium chronic = 50 u 1 <br />Total Trivalent Chromium chronic = 1000 u <br />Total Hexavalent Chromium chronic = 1000 u <br />Total Recoverable C er chronic = 500 u <br />Total Recoverable Lead chronic = 100 u 1 <br />Total Recoverable Selenium chronic = 50 u 1 <br />Tota] Recoverable Selenium acute and chronic = existin li tem or modification throu b 2/28/09' <br />Total Recoverable Zinc chronic = 25000 u <br />• Temporary modification applies to Johnson Gulch below confluence with Pyeatt Gulch only <br />III. Water Quantity <br />The Colorado Regulations specify the use of low flow conditions when establishing water quality <br />based effluent limitations, specifically the acute and chronic low flows. The acute low flow, referred <br />to as 1 E3, represents the one-day low flow recurring in athree-year interval. The chronic tow flow, <br />30E3, represents the 30-day average low flow recurring in a three-yeaz interval. <br />Low Flow Analysis <br />Although there is periodic flow in Johnson Gulch, No Name Gulch, Faz East Buzzard Gulch, Coyote <br />Gulch, Ute Gulch, Middle Pyeatt Gulch, East Pyeatt Gulch, West Pyeatt Gulch, Deer Gulch, Grouse <br />Gulch, Sage Gulch, Oak Gulch, Horse Gulch, West Horse Gulch, West Flume Gulch, Middle Flume <br />Gulch, East Middle Flume Gulch, East Flume Gulch, and Deal Gulch upstream of the Trapper <br />Mining, Inc. WWTF, the lE3 and 30E3 monthly low flows aze set at zero. For this analysis, low <br />flows aze summarized in Table A-3. <br />Appendix A Page 4 of 8 Draft <br />