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COLORADO DF_/',4 X7iNENT OF !/EA477l, li'utr•r Quality Contra! Di+•i.cion Rntinnnlr• - l'gr;r 14, Prnnit Nn. C.O~.(2(.t~Y Tam! Residual Chlorine: Water quafity-based efjlurnt linuuuiorrs mere evaluated jot total re+idunl chlorine. Since the permit[ee rloec not chlorinate am• uj (he effhrenr wa+~(e+(rearns, uruil resuiuu( chlar are is nor upected to be present in the discharges. Therefore, no linvts or monimring requirernenr.c will be adopted in the permit for rota! residual chlorine. Toro( Anvrwnia: Similar to the above discussion jot total residual chlorine, rata! anvnonia is oat expected to be present in the discharges. Therefore, rto lirni[ or monitoring jot ammonia will be required. Meta Ls: For rnuais with dissolved standards, corresponding effluem limits are based upon the potentially dissolved method of analysis. For standards based upon the total and total recoverable methods of analysis, the limits art based upon the same method as the standard, eccept jot arsenic. For arsenic, the total recoverable analysis must be performed using a graphite furnace. Table VIA lists the effluent limits that were calculated. A comparison of the limits comained in Table V/-6 and the e,[fluem concentrations at Otufall 006, reported in the permit renewal application and contained in Appendix A to this rationale indicated that the Permittee exceeded the water quality-based effluent limitations for total mercury, potentially dissolved manganese, and sulfate. Iherefore, water quality-barrel effluem limitations far these parameters will be incorporated imo the proposed permit. In addition, the previous permit establrshed water quality-based efjluem limitations far total recoverable iron. Since the rrost stringent criteria for iron rs a potentially dissolved method of analysis, monitoring of potentially dissolved iron will be adopted in the proposed permit. Bared on a comparison ojthe limits in Table V/-band the reported eBluent concentrations contained in Appendix A, no problans in complying with the potentially dissolved iron egluem limit is expected. d. Anrideeradation -Pursuant to section 3.I.8(IJ(6J of The Basic Standards and Methodoloeies far Surface Water, an amidegradation review is not required for this permitting action. e. Sa/inity Regulations: /n compliance with the 'Regulations for Implementation of the Colorado Salinity Standards Through the CDPS Permit Program', the perrnittee shall moni[or for total dissolved solids on a quanerly basis. Samples shall be taken at the effluent discharge point(s). Salinity requirements are included in Part I, Section B.3 of the permit. f. Whole Effluent Tosieity (LVETI Ttsting For this facility, chronic WETler~ing it requrred at OtufaU 006. (See Para I.A and /.B ojtht permit.) aJ Pumose of WET Testing: The Water Quality Control Division has established the use of WET testing as a method for idem~ing and controlling toxic discharges from wastewater treatment facilities. WET testing is being utilized as a nuaas to ensure that there are no discharges of pollutants "in amounts, concentrations or combinations which are harmful to the beneficial uses or toxic to humans, animals, plants, or aquatic life" as required by Section 3.1.11 (IJ(dJ of the Basic Standards noel Methodologies (or Surface Waters. 6J /nstream Was[c Concentration (IWC1: Where monitoring or limitations for WET are deemed appropriate by the Division, chronic instrcam dilution as represented by the chronic IWC is critical to determining if acute or chronic conditions apply. For those dischorges where the chronic IWC rs greater than (>J 9.1 %, chronic conditions apply, where the /WC is less than or equal to (<_J 9.1 acute conditions apply. The chronic /WC is determined using the following equation: IWC = /Facility Flow (FFJ/(Stream Chronic IJow Flow (annual) + FFJ/ X 100%