COLORADO DEPARTMENT OF HEATH, Water Ounlity Division
<br />Rmionnle - Pnge 9, Permit No. CO-0043648
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<br />P Dischar a Limitations ti
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<br />ff
<br />arameter
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<br />30-D Avera e
<br />Dail Max.(Min./Max.
<br />or H ona
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<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
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