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<br />COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Summary of Rationale - Page 9. Permit No. CO-0042439 <br />VII. TERMS AND CONDITIONS: <br />A. Effluent Limitations: <br />The following limits will apply and are discussed in Sections VII-B <br />and VII-C. <br />Table VII-1 -- Effluent Limits <br />Parameter <br />Limit <br />Rationale <br />Flow, MGD <br />BODS, mg/1 Clb/day) <br />TSS, mg/1 (lb/day) <br />Fecal Coliform, 9/100 ml <br />Total Residual Chlorine, mg/1 <br />pH, s.u. <br />Oil and Grease, mg/1 <br />Total Ammonia as N, mg/1 <br />0.060a <br />30(15)/45(22.5)b <br />75(37.5)/110(55)b <br />6,000/12,OOOc <br />O.Sd <br />6.5 - 9.Oe <br />lOd <br />Reportd <br />Design Capacity <br />State Effluent Limitations <br />State Effluent Limitations <br />Fecal Coliform Policy <br />State Effluent Limitations <br />Water Quality Standards <br />State Effluent Limitations <br />Water Quality Standards <br />a 30-day average d Daily Maximum <br />b 30-day average/7~ay average a Daily Minimum-I4aximum <br />c 30-day geometric mean/7-day geometric mean <br />B. Calculation of Si'ater Quality Based Effluent Limitations: <br />A mass balance equation is used to determine the effluent <br />concentrations that would not violate the allowable in-stream <br />concentrations defined by the Water Quality Standards for the stream <br />segment in question (See Rationale, Section III); except in the case <br />of pH, where the: limits are set directly from stream standards or <br />effluent regulations without using a mass balance approach. The mass <br />balance equations is: <br />M,~ _ ~~ - MtQI, where: <br />'" Q2 <br />Ql = Upstream low flow from Part III.B.2 <br />Q2 = Monthly average effluent flow (design capacity) <br />Q3 = Combined downstream flow (Q1 + Q2) <br />Ml = Upstream background pollutant concentration from III.B.1 <br />M2 = Unknown; Maximum allowable effluent pollutant <br />concentration calculated using mass balance equation <br />M3 = Maximum downstream allowable pollutant concentration <br />(stream standard) <br />A summary of the mass balance calculations (if any) are shown and <br />discussed in VI I.C. <br />