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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale -Page IS, Pctmit No. CO-0034142 <br />Tab-t ViT-S - Aeute and Chmttit Flows (R'il/ia»ts Fork River) <br />;:;:Flow.' ::::::::..:::.::";:.;.:;::::;::':.:.::Aciitl:;.(lE3}.'::;;:;~:;":.::::::_':;G7eronic:(30i?3).; ;,:;:;.,:: <br />Qt 42 cjs 48 cfs <br />Q= 6 28 cfs' 6.28 cfs <br />Qt 48.28 cfs 54.28 cfs <br />Values for Q2, the average daily ejJluent flow (design capacity) as done in the previous permit, were <br />calculated from tht sutrumtion of maximum floxts for OutfaUs 003, 022, an4 024. Outfall 003 has a <br />design capacity of 21700 gpm (4.46 efsJ and OutfaU 024 has a design capacity of 400 gpm (0.92 cfsJ. For <br />OutfaU 022, the previous permit assumed a maxinwtn flow of 128 gpm. This information was provided by <br />the pmnittee in May 1986. 71st permittee also rtported that by tht twemieth year of operation, the <br />ef/luent !low is expected to be 787 gpm <br />As shown in Table V-3, the ofjlutm flow from Outfall 022 rsceeded 128 gpm. The maximum flow reported <br />during 1992 was 132 gpm Therefore, for purposes of calculating water quality-based efjiuem limitations, <br />it wxu assumed that the maximum flow from Outfall 022 during the Wert five ycars will be 394 gpm (0.9 <br />cfsJ, half the flow expected to discharged by year 20. This results in a total combined flow limit of 6.28 <br />cfs (4.06 MGD! for all three outfalls. Thus, the discharge flows should remain within this limit jar the life <br />of the permit. <br />Based upon a design capacity of 0.012 MGD (0.019 efsJ, water quality-based effluent limitations for total <br />resulual chlorine, as done in the previous permit, were calculated at Dutfall 023. Although the previous <br />permit rationale indicated that the wastewater flow wiU increase to 0.022 h(GD within 5 to 1 D years, the <br />reported flow values in Table V-1 indicate that the effluent flows have not exceeded 0.012 MGD. <br />Therefore, as done in the previous permit, effluent limitations will be calculated at Outfall 023 based on a <br />maximum flow of 0.012 MGD. The cfjlucnr limits are shown in Table V]-3. <br />Values jar M, and Mt vary deptnding on the background stream quality data (M~J and the applicable <br />water quality standard (hftJ. Values for MI are provided in Table If/-3. k(3 values are shown in Table <br />VI-6 along with the calculated t.Qluent limitations (MtJ for Outfallr 003, 02.?, and 024. <br />