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COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENV/RONMENT, Water Qunliry Control Division <br />Rationale - Pnge 6, Permit No. CO-0036595 <br />Table V/-3 -- Federal Standards (40 CFR 434) <br />• Pammeter Limitations <br />30 Dav Av;¢ Concentration Dhi/v Max. Concenlmtion <br />pH, s. u. (minimum - maxirnumJ ---6.0 - 9.0--- <br />Tornl Susperuled Solids, rag/Q* 35 70 <br />Torn! Iron, mg/P* (BAT**) 3.5 7.0 <br />Settleable Solids. m P/t * N/A 0. S <br />• 7lrrsr parameters subject ro Runien of Proof Requirements, srr nest section <br />•• Brst Avaitab(c 7cchno(ogy <br />Alternate Limitation Burden of Proof Requirements: /n cos formance with 40 CFR 434.63, the penuinee has the <br />burden of proof when requesting relief from tarn! susperuled solids (TSSJ, rota! iron nrrd/or settleable .solids <br />limitations, ns appropriate. The intent of this regulation is to afford relief only when needed due to n valurrre of <br />water gerrernred by n specific storm evert, it is not irrterrded to be automnticnlly applied (o n[[ dischnr-ges cnuserl <br />by precipitnriorr, nor to 6e used to discharge volumes irr excess of that generated by the storm event. Orr this <br />basis, reliejshall be grunted only when rrecessnry and shall Trot be granted when the permittee has control over <br />the discharge, errnblirrg them to meet the primary linritatioru. The permittee should endeavor ro meet tl~e <br />primary lin+itatiorrs whenever possible. Because marrun! dewatering can be accomplished ns rime nrrd corrdirinrrs <br />permit, all mnnun! dewnrering shall be required to meet the primary limitations. The Division shell detenrrirre <br />the adequacy of proof. As port of this determirrntiorr, the Division shn[l evaluate whether the permittee could <br />hove corrtro[led the discharge in such n manner that primary limitations cou4( have been met. <br />For snit fell, to waive 7SS and total iron limitntiorrs, it is necessary to prove that discharge directly resulted <br />from a specifrc event oral occurred through autonrntic dewnterirrg devices within 48 hours after nrensurnble <br />• precipitatio» has stopped. In ruiditiorr, to waive settleable solids limitntiorrs, it is rrecessnry to prove that err <br />event greater then the mngrritude of the 10-year, 24-hour event occurred. <br />For snowmelt, to waive 7SS arui total iron limitntiorrs, it is necessary to prove that discharge directlyresulted <br />from snowmelt acrd occurred through automatic dewntering devices within 48 hours after pond ir~o+v has <br />stopped. In rulditiorr, to waive settleable solids limitntiorrs, it is mecessnrv to prove that err event greater than <br />the magnitude ojthe applicable 10-year, 24-hour event occurred. <br />c) Antiderrndntiwc Since the receiving wnrer is Use Protected, err nnridegrndntion review is not required pursunnr <br />ro section 3.1.8(/J(bJ of The Basic Stnrrdnrds nrrd Methodoloeies for Surface Water. <br />dJ Whole ENluerrt Toxicirv (WET1 Testirre: For ourjnl! 004, acute WET testing is required. (Set Ports I.A. /. (bJ <br />nrrd /. A. 2. of the permit. J <br />I J Purnore of WET Tesrinr: The Water Qunliry Comrol Division has established the use of WET testing ns n <br />method for ident~ing and controlling toxic discharges from wnstewnrer treatment fncilitier. WET testing i.c <br />being utilized ar n means to ensure that there ore no discharges ojpollurants "irr nnmuutr, concerurntions <br />or combirrnriarrs which ore harmful to the berreficin! uses or toxic to humnru, nrrinrnls, plnrrts, or nquntic <br />life" as required by Section 3.1.11 (IJ of the Basic Smndnrds tins! Methodoloeies (or Surface Wmers. <br />2) Grstrenm Waste Cancemtrnrion (IWC): Where monitoring ar limitations for WET ore deemed npproprinte by <br />the Division, chronic instream dilution ar represemred by the chronic IWC is critical in determining whether <br />ncure or chromic car+ditiorrs shall apply. For rho.se discharges where the chronic 1WC is greater thnrr (> J <br />9. / %, chromic conditions apply, where the /WC is less rhm+ or equal ro (<) 9. l ncure cnnditio_u.a apply. <br />The chromic lWC is determined using the jo!lowirrg equmiorr.• <br />• lWC = fFnciliry Flo+v (FF)/(Stream Chronic Low Flow (nrurunl) + FFJ/ X /00% <br />The flows and corresponding IWC for the npproprinte discharge poirrr follow. <br />