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Oxbow Mining WWTF Water Quality Assessment CO-0000132 <br />lII. 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-yeaz interval. The chronic low flow, <br />30E3, represents the 30-day average low flow recurring in a three-year 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 Quali Control Commission Re lation 35 <br />Calculated Using the Following Value for Hazdness as CaCO3: 400 mg/1 <br />Parameter In-Stream Water <br />Quality Staadard <br />Formula Used <br /> <br />d <br />i ACUte 19 ug~l [1.13667-0.041841n(hardness)][e(1.126(In(hazdness)}3.6867)] <br />ssolve <br />Cadmium, D ChTOI11C 6.2 Ug/1 [1.10167-0.041841n(hardness)][e (0.7852Qn(hazdness)}2.715)] <br />Hexavalent Chromium, Acute 16 ug/1 Numeric standazds provided, fomwla not applicable <br />Dissolved ChLOIllC 11 llg/1 Numeric starMarSS provided, fornaila not applicable <br />Di <br />l <br />d <br />Acute <br />50 ug/1 <br />a (o.9azzpn(naraness>}1.7aos) <br />sso <br />ve <br />Copper, ChrOn1C ~ 29 ug/1 a (0.8545(In(hardness)}1.7428) <br /> <br />M Acute 4738 ug/I e(0.3331(ln(hardncss)}W.4676) <br />anganese <br />ChrOIDC <br />2618 llg/1 <br />e(0.3331(In(hardness))+5.8743) <br /> <br />k <br />i <br />l Acute 1513 ug/1 a (o.aa6Qn(nardness)}tz.zs3) <br />el, D <br />ved <br />Nic <br />sso <br />Chronic <br />168 ug/1 <br />a (o.sa6(m(haraness>)+o.oss4) <br /> ACUte 18 u Numeric standards provided, formula not applicable <br />Selenium, Dissolved <br />ChrOIllC <br />10.6 llg/1 <br />TertWorary modification through l2-31-06 <br /> <br />Sil <br />Di <br />l <br />d Acute 22 u % e ('.7zpn(i>ardness)}6sz> <br />ver, <br />sso <br />ve Chronic 3.5 u e(1.7z(In(lurdness)}9.o6> <br /> Acute 379 ug/1 a (0.6473(In(bazdness))+(1.86I8) <br />Zinc, Dissolved <br />ChrOT11C <br />3$2 Ug/l <br />e(0.8473(ln(hardness))*0.8699) <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 1 E3 and 30E3 monthly low flows are set at zero based on information provided by <br />local Water Commissioners. For this analysis, low flows aze summarized in Table A-4. <br />Appendix A Page 5 of 10 Draft <br />