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<br /> <br />COLORADO DEPARTMENT OF HEALTH, Water Quality Control iivision <br />Rationale - Page 12. Permit No. CO-0027146 <br />VI. TERMS AND CONDITIONS OF PERMIT <br />A. Effluent Limitations (continued) <br />1. Aoolicable Federal Effluent Guidelines .snd Standar'_s: (continued) <br />For rainfall, to waive TSS and total iron limitations, it is <br />necessary to prove that discharge occurred within 48 hours after <br />measurable precipitation has stopped. In addition, to waive <br />settleable solids limitations, it is necessary to prove that <br />discharge occurred within 48 hours after precipitation greater <br />than the 10-year, 24-hour event has stopped. <br />For snowmelt, co waive TSS and total iron limitations, it is <br />necessary to prove that discharge occurred within 48 hours after <br />pond inflow has stopped. In addition, to waive settleable <br />solids limitations, is is necessary to prove that discharge <br />occurred within 48 hours after pond inflow volume greater than <br />the 10-year, 24-hour event has stopped. <br />The Division shall determine the adequacy of proof. As part of <br />this determination, the Division shall evaluate whether the <br />permittee could have controlled the .discharge in such a manner <br />that primary limitations could have been met. All manual <br />dewacering must meet TSS and total iror. limitations. <br />2. Water Quality Standard Based Effiuent Limitations: A sass <br />balance equation was usad co calculate potential effluent <br />limitations for outfalls 001 and 002 for total recoverable <br />iron. There are no me cols standards applicable to oucfall 004 <br />which discharges to Coal Creek. The mass balance equation is: <br />M2 M3Q3 - M1Q1~ <br />Q2 <br />Where: Q1 ~ Ups cream low flow from Part III.B.1 (Colorado fiver) <br />Q2 - Effluent flow from Part II.F <br />Q3 - Combined downstream flow (Q1 + Q2) <br />M1 - Upstream background pollutant concentration <br />M2 - Unknown; effluent pollutant concentration <br />M3 - Water Quality Standard <br />A summary of Che mass balance calculations are shown and <br />discussed in Table VI.4. <br />The values for Q1, Q2 and Q3 are the same in all of the <br />calculations for water quality limited parameters and are: <br />