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COLORADO DEPARTMENT OF HEATH, Water Ounlity Division <br />Rmionnle - Pnge 9, Permit No. CO-0043648 <br />E <br />l <br />P Dischar a Limitations ti <br />l <br />R <br />ff <br />arameter <br />uent <br />30-D Avera e <br />Dail Max.(Min./Max. <br />or H ona <br />e <br />a <br />Be innin Februa 1, 2003 3,674 5,905 W S <br />Zinc, Potential! Dissolved, /1 <br />Throu hJanua 31,2003 Re ort** Re ort W S <br />Be innin: Februa 1, 2003 600** Re ort W S <br />Limits A lieable Durin Tem ora Standards Modi tendons -E ective Throu h 12/31/07 <br />H, su (minimum-maximum) N/A 5.6-9.0 WQS <br />Limits Based U on Under! in Standards or Parameters With Tem ora Modi tcntions - E ective Be inning 1/1/08 <br />H, su (rnintmurn-maximmn N/A 6.0-9.0 WQS <br />NV =None Visible. rn die event nn ail sheen orflonting off is observed, n grub snnrpleshnll be collected nnnlyed reported, and evaluated relative to the 10 nrg/I doily nrasinumr <br />value. N/A =Nat Applicable. <br />'For cyanide, the TVS standard for the receiving srrenrn is based upon 'free "ryanide concentrations, which is tess than the 'free "cyanide anatylicol defection limi[ While llte limit <br />wilf be set equal to the stream standards, this permit nllmvs zero to be used in dte cnlculmion afreporting values whenever nn nnnlytirn/ result is less than tde detection limit. As such, <br />any'Iree"cyanide cancennatiau less Than the urcolytical detection limit frill be considered to be zero. <br />* * 77ris limit is Nre 85th percentile vnbte of the nttrtlyticnl results ofsnrnples collected nt Outfnll OO/A for the most recent 60 months Including the month for which the discharge is <br />being reported and cn(culmed sing the Min'otofi Excel 85°i percemi/efmdion <br />Table VI-2 <br />Limits for Outfal1005B -Limits far Annual Precipitation Exemption <br />from "No Discharge"{nom the VLF to Arequa Gulch as measured at AG-01.5. <br /> <br />' ', Effluent Parameter <br />r'• > ' `'°Dischar etirititahons~ =' <br />~~` ~ <br />30-Da Averri e~~ '' Dail Mas r - ' <br />r ~ ~~ Rationale <br />Flow, MGD Re ort Re ort Dischar a Assessment <br />TSS, mg/1 20 30 Effluent Limit Guidelines <br />(EEGs <br />Oil and Grease, m /l NV 10 State E uent Re lotions <br />Ammonia, Total, /I l ns N Re ort Re ors W S <br />Co er, Potential! Dissolved. /1 150 300 EEGs <br />Lead, Potentially Dissolved, /1 300 600 EEGs <br />Mercu ,Total, /1 1 2 EEGs <br />Nickel, Potential! Dissolved, /1 Re ort Re ort W S <br />C anide, Free, R Re ors Re ors W S <br />Alumir:unt, Potential! Dissolved, R Re ors Re ors W S <br />Cadmium, Potential! Dissolved, /1 SO 100 EEGs <br />Iron, Total Recoverable, /1 Re ors Re ort W S <br />Man anew, Potential! Dissolver! /1 Re ors Re ors W S <br />Zirte, Potential! Dissolved, /1 750 1,500 EEGs <br />H, su (minimum-maximum) NA 6.0-9.0 EEGs <br />NV =None Visible. /n the event mr oil sheen arJloming oil is observed n grub snnrp/e shnll6e collened analyzed, reported and evnhm[ed relative to 1lte /0 ntg/l doily mnxinnnn <br />value. N/A =Not Applicable. <br />• For ryanide, the TVSslandard for the receiving strewn is based upon 'free "ryanide concentrations, which is less dran the free"ryanide analytical detection limit. While dre limit <br />will beset equal to the strewn smndnrds, this permit allows zero to be ¢seAin the cnlndntion afreporting values whenever nn nnnlyticnl result is less than tlredetecrion limit. As such, <br />any ';free"clnnide concentrations less Than the analytical detection limit will be considered zero. <br />2. Discussion of Effluent Limitations <br />a) StateRegulntionsforEfJluentLimitations:TheRegulationsforEffluentLimitations(Regulation62),applytotheconventional <br />pollutants -BODs, TSS, pH, oil and grease, and total residual chlorine. For this facility, the only conventional pollutants of <br />concern are TSS, pH, and oil and grease. The limitations in Regulation 62 for oil and grease and TSS will be applied. For <br />pH, the limits in Regulation 62 are more stringent than the TemporaryModification and underlying standard that have been <br />adoptedfor Arequa Gulch. Pursuant to Regulation 62, Sech'on 62.3(3), since effluent limitation guidelines do not apply to <br />Outfall OOIA and to discharges under the Storm Exemption Fram Federal Effluent Limitations for Outfa11005B, pHlimitsfor <br />these outfalls will be based upon: the applicable water quality standard for pH. <br />b) Pollutants Limited by Water Quality Standards -The Water Quality Control Division has performed an assessment of <br />potential water quality standards-based assimilative capacities and made a deterntination of the assimilative capacity of <br />Arequa Gulch and Cripple Creekfor the pollutants of concern. This assessment is attached as Appendix A afthe rationale. <br />In comparing the ambient water quality data jot rnonitoringpoints AG 1.5 and AG 2.0, shown in Figure 3 oftlre Pennit, there <br />is a clear improvement in the water quality in Arequa Gulch for parameters, which were monitored at both locations. This <br />