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COLORADO DEPARTMENT OF~ALTH, Water Quality Control Divition • <br />Rationale -Page 2, Permit No. 00.0024562 <br />In order to taleulate water quality based ej/luent limitations, the fallowing mass batance equation will be <br />used: <br />M3Q3 - M]Ql <br />M2 = <br />Q2 <br />Where: <br />Qt = Upstream low flow (l E3 or 30E3) <br />QZ = Averoge daily effluent flow (design capacity) <br />Qp = Combined downstream flow (QI + Q~ <br />Ml = Upstream background pollutant wncentrotian <br />M2 = Unknown; Maximum allowable cfjRuent pollutant cancentrotian calculated using mass <br />balance equation <br />M3 = Maximum downstream allowable pollutant eoncentrotion (stream standard) <br />The same upstream low-flows, upstream pollutant conuntratians and discharge Jlowrotes listed ta the <br />original permit rationale will be used to eakulau the earneded e~(lluent limits. And, as was done in the <br />original permit, limits will be calculated for two d(,(jerent design flows -one being 2.58 MGD, which <br />represents the expected maximum flow when no underground explorotion or mining is occurring, and a <br />second design flow oj3.76 MGD, which represents the maximum expelled flow when underground <br />exploration or mining is occurring. <br />The values for the variables listed above are summarirRd in the following table: <br />Srmm~a- o~EA7rtent l~ <br />Caleulattons !: ;:;NoUrdegrowid;::'::';:;;;. <br />>:::.:. '.;;' UrufeigmundOpetgtians:::.: <br /> Chronle Acute Chronic Acute <br />Qt -Upstream Low-FTaw (cis) 6.8 6.8 6 8 6.8 <br />Q2 -Design Flaw (efs) 4.0 4.0 6.0 6.0 <br />Qg -Combined Downstream Flaw (cjs) ]0.8 10.8 I2.8 I2.8 <br />MI -Upstream Zinc Concentration <br />(rng/9 0.0094 0.0094 0.0094 0.0094 <br />Mg -Zinc Stream Standard (mg/1) 0.207 0.228 0.207 0.228 <br /> <br />My -Calculated E,Q7uent Limit 0.54 0.60 0.43 0.48 <br />The calculated limits in the above table wen compared to federal ejlluent guidelines, which would only <br />apply during auive mining operations. The calculated limits, in all cases, are more restruxive than the <br />federal guidelines, and shall therefore be directly incorporated into the permit. This shall be done through <br />the amerulmem ojpages la and 16. <br />B. Discussion o(Future Cresson Pit Mining Operations <br />The CC&V Mining Company is expanding its cyanide heap leach mining operations, which will involve the <br />removal of ore from the Cresson Mine, crushing it, and then depositing it for leaching in the valley which <br />forms Arequa Gulch. <br />