2005-12-02_PERMIT FILE - C1981019

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COLORADO DEPARTMENT OF Pt/BLIC HEALTH AND ENV/RONMEM', Water Quatiry Cortrraf Division Rationale -Page 6, Permit No. CO-0045161 Parameter isc arge imitations Maximum Concentrations Rationale - ay vg. ai y ax. Total Recoverable Iron, mg/1(Beg;nn;ng/anuary /, 2008) 1.0 Report ater ua ity tan ar s ett ea e o i s, m Re art .S Fe era E uent ui a Ines i an rease, m Re ort 1 tote vent a ations pH, s. u. minimum-maximum A 5- . afer ua ity tan ar s TE , mg 2A on yf Report est ro essiona Ju Bement Tota isso ve o i , mg Report eport River a inity tan ar s "Ta/ol Suspended Solids and Total iron limifarionS are Primary Limilations, and J'etf(eable 3oads (+mdanons are Alternate Lrm+taaorzs. Clem rloxjrom these limiralions due to storm evenGS is subject fo burden of proof requirements -see section VLA.2.6). ""BTEX monitoring will be required only if the Washbav Pond discharges inla the Work Area Pond 2. Discussiono,~Ef/IuentLimiiations: a) Renilations for E uent Ltmitanbns: The Regulations (or Effluent Limitations Re lotion Na. 62 (5 CCR 1002-62f, app y to t e conventiona po utants. For this facility, the limitations for Oil and rease are based on this regulation. b) A licable Federal E uent Guidelines and Standards: The federal guidelines that apply to this type ofjaciliry are ound under 40 C R 434, tit ed Coal Mining Point Source Effluent Guidelines. The limitations that applly follow. Tahle VI-2 -- Federal Standm~ds (40 CFR 4341 Parameter imttations 3 try Avg ai y ax H, s. u. minimum -maximum .0 ota Sus en e of m 35 70 ota Iron, m BA 3.5 7. err ea e o i s, m 0.5 ese parameters su ject to ur en o too eguiremexts, see next section est vai a e ec no ogy-app ies to t ose po area constructe Alternate Limitation Burden o Proo Re uiiemenu: In conformance with 40 CFR 434.63, the permittee has the burden o proo when requesting relie om rota suspended solids (TSS), total iron, and/or settleable solids limitations, as appro riate. The intent ofthis regulation is to afford reliefonly when needed due to a volume ofwater generated by a sped rc storm event; it is not intended to be automatically applied to all discharges caused by precipitation nor to be use to discharge volumes in excess afthat generated by the storm event. On this basis, re tefsha l be granted only when necessary and shall not be granted when the permittee has contra[ over the discharge, enabling them to meet [he primary limitations. The permittee should endeavor to meet the primary limitations whenever possible. Forponds with automatic dewatering structures, only discharges through these structures are eligible or the exemption. All manual dewatering of ponds that are equipped with automatic dewatering systems must meet SS and total iron limitations. Ifa pond has only manual dewatering capability (no riser pipes or other automatic dewatering systems), relief is available only to the extent required to regain necessary capacity required byregulations. Additional dischargge flow shallmeetprimarylimitations. The Division shall havefrnalau[horityrndeterminingwhetherreliefisgranted A11 outfalls are eligible for this ezemption except 002A, because it commingles with vehicle washwater. Documentation that the treatment facilities were properly operated and maintained before and during the storm event shall be submitted with any request for relief as an attachment to the Discharge Monitoring Report (DMR/ for the appropriate period, and theDivision shall determine the adequacy ofproof. As part ofthis determination, the ivision shall evaluate whether the permittee could have controlled the dischharge in such a manner that primary limitations could have been met, whether proper sediment storage levels were maintained, and the ponds had sufficient water and sedimentcapacityfarthestormeventplusotherrelevantfactors. Weathersiationdatamaybeapproprtateforrainfall For rain all to waive TSS and total iron limitations, it is necessary to demonstrate that discharge occurred within 48 hours a ter measurable precipitation has stopped To waive settleable solids limitations, it is necessary to prove thdt discharge occurred within 48 hours after precipitation greater than the 10 year, 24-hour event has stopped For snowmelt to waive TSS and total iron limitations, it is necessary to demonstrate that discharge occurred within 48 ours after pond inflow has stopped. To waive settleable solids limitations, it is necessary to prove that discharge occurred within 48 hours after pond inflow volume greater than the 10-year, 24-hour event has stopped c) Pollutants Limited by Water Quality Standards.' The Water Quality Assessment to Appendix A is an evaluation of po !utants limited by water quality standar T e mass balance equation shown in Section IV o jAppendix A was used for pollutants to calculate the maxrmum allowable a uent concentration, Mz, that could be discharged without causing the water quality standard to be violated A detailed discussion of the calculations for the maximum allowable e{lluent pollutant concentrations forfecal coli orm, total residual chlorine, ammonia and metals is provided in Section l ofthe water quality assessment containe in Appendix A. The maximum allowable effluent pollutant concentrations determined as part ofthese calculations represent the calculated a went limits that would beprotecttve ofwaterquality. These are also known as the water quality-based effluent limits QBELs). The Permits Unit evaluated the calculated WQBELs and has made a determination as to whether there is a reasonable . potential for thejacility discharge to cause or contribute to an exceedance ofa stream standard. Ifthere is a reasonable potentia for the discharge to contribute to an exceedance, effluent limits are included in the permit. i. Metals -Utilizing the assimilative ca acities contained in Appendix A, an analysis must beperjormed to determine whether to include the calculated WPBELs in the permit. T he guidelinesfor performing a quantitative reasonable potential (RP) analysis are outline~n the Division's document, Determination ofthe Requirement to Include Water Revised 1242005