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