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Oxbow Mining WWTF Water Quality Assessment CO-0000132 <br />III. Water Quantity <br />T'he 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 low flow, <br />30E3, represents the 30-day average ]ow flow recurring in a three-yeaz interval. <br />Table A-3 <br />TVS-Based Metals Water Quality Standards For CO-0000132 <br />Based on the Table Value Standazds Contained in the Colorado Department of Public Health <br />and Environment Water uality Control Commission Re lation 35 <br />Calculated Using the Following Value for Hazdness as CaCO3: 400 mp/1 <br /> <br />l <br />d <br />C <br />d <br />i <br />Di Acute 19 ug/1 [1.13667-0.041841n(hardness)][e~~ "op~que~~~~cs~l-~.oouip <br />sso <br />ve <br />m <br />um, <br />a C1ITOIDC 6~.2 llg/1 [1.10167-0.041841n(hardncss)][e (0.7852(In(hardness)}2.715)] <br />Hexavalent Chromium, ACllte 16 Ugll Numeric standards provided, formula not applicable <br />Dissolved Chronic 11 ng/1 Numeric standards provided, formula not applicable <br /> <br />l <br />d <br />Di <br />C Acute 50 ug/1 a (0.9422Qn(hardness)}1.7408) <br />ve <br />opper, <br />sso Chronic . 29 Ug/l a (0.8545(ln(hardness)}1.7428) ` <br /> <br />M Acute 473$ llg/1 e(0'3331(ln(hardness)}+6.4676) <br />anganese <br />Chronic <br />2618 u (0.3331(In(hardness)}tiS.8743) <br />e <br /> <br />Di <br />l <br />d <br />Ni <br />k <br />l Acute 1513 ug/1 a (0.846(In(hardness))fi2.253) <br />sso <br />ve <br />c <br />e <br />, Chronic 168 ug/I e (osaepnparaneu)}~o.ossa) <br />l Acute 1$ ll Numeric standards provided, formula not applicable <br />ved <br />Selenium, Disso Chrome lO.6 ug/] 'Temporary nrodifiwtion tinough l2-3t-06 <br />Di <br />d <br />Sil <br />l <br />Acute <br />22 u <br />~ e (I.npn(naraness}}-b.sz) <br />sso <br />ve <br />ver, Chrome 3.5 llg/1 a (1'72(In(hardness))-9.06) <br /> <br />d <br />Zi <br />Di <br />l Acute 379 u e (0.8473(ln(hardness)}M.8618) <br />sso <br />ve <br />nc, Chrome 3$2 llflll e(0.8473(ln(hardness)}F0.8699) <br />Low Flow Analysis <br />Although there is periodic flow in Sanborn Creek and Elk Creek upstream of the Oxbow Mining, <br />LLC W WTF, the lE3 and 30E3 monthlylow flows are set at zero based on information provided by <br />local Water Commissioners. For this analysis, low flows are summarized in Table A-4. <br />Appendix A Page 5 of 10 Draft <br />