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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale - Page 15. Permit No. CO-0027154 <br />VI. TERMS AND CONDITIONS OF PERHIT <br />A. Effluent Limitations (continued) <br />The mass balance equation for all metals limitations is: <br />Mz - M3Q3 - MiQi. <br /> <br />Where: Q1 <br />Qz ' <br />Q3 <br />M1 <br />Mz , <br />M3 , <br />Upstream low flow from Part III.B.1 <br />Effluent flow from Part II.F <br />Combined downstream flow (Ql + Qz) <br />Upstream background pollutant concentration <br />Unknown; effluent pollutant concentration <br />Water Quality Standard <br />A summary of the mass balance calculations are shown and discussed in <br />Table VI.4. <br />The values for Q1, Qz and Q3 are the same in all of the calculations for <br />water quality limited parameters and are: <br />Acute 6 Chronic Limitations <br />Q1 0 MCD <br />Qz 1.26 MGD (combined flow for outfalls 001, 005 and 007) <br />Q3 1.26 MGD (combined flow for outfalls 001, 005 and 007) <br />Values for M3 are shown in Table VI-8. Also shown in Table VI-8 are the <br />calculated effluent limitations (Mz). Because the low flow is zero, the <br />upstream concentrations (M1) are assumed to be zero. Also as a result of <br />the zero low floe, the effluent limitations equal the water quality <br />standards regardless of the discharge design flow. <br />Table VI-8 -- Summary of Mass Balance Calculations <br />Upstream Background Stream Effluent <br />Concentration Standard Limitation <br />Acute/Chronic Acute/Chronic <br />Parameter (M1) (M3) (Mz) <br />Total Recoverable Iron, mg/1 0 -/1.0 -/1.0 <br />Total Recoverable Manganese, mg/1 0 -/1.0 -/1.0 <br />Potentially Dissolved Copper, mg/1 0 0.130/0.073* 0.130/0.073 <br />Potentially Dissolved Silver, mg/1 0 0.079/0.003* 0.079/0.003 <br />* based on a mean hardness value of 839 mg/1 - equal to the adjusted mean of all effluent <br />hardness data on file (no instream hardness data were available) <br />