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;OLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Qua(iry Control Division iationale-Page 5, Permit Na. CO-0038776 _ For rainfall, to waive TSS and total iron limitations, it is necessary to prove that dzscharge occurred within 48 hours after measurable precipitation has stopped. In addition, to waive settleable solids limitations, it is necessary to prove that 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 necessa to prove that discharge occurred within 48 hours occurpred within 48 hours after pond infloiw volume greater! thanethel] D- lean 24-hour event has at ppedrove that discharge Documentation that the treatment facilities were properly operated and maintained prior to and durin the storm event must be submitted with any request for relief. The Dzv:szon shall determine the adequacy of proof. As part of this determination, the Division shall evaluate whether the permittee could have controlled the discharge m such a manner that primary limitations could have been met, whether proper sediment storage levels were maintained and the pondggs had m~tiTSS and tota~ironi 1 nzitations unlesstprevious app o~alshashbeenlgranted for ponds that have o other methoduaf dewatering. P~ost-Minin Areas: In conformance with 40 CFR 434.50, commencing at the time active mining has ceased and all surface areas sen'ed by a sedimentation pond have been returned to the required contour and reveggetanon has commenced, applicable discharges may be eligzble for limitatons other than those spec[~ied in Part LA.1. ]n most cases, these post- mintng Itmitations shall remain in effect until bond release. The permittee shah not[{y the Division at the ap ropriate time so that consideration o(permil modifications can be made. Prior to notificatiors anzfsubsequent permit modi/~cahon, active mining limitations will apply regardless of aelual mine status. Pollutants Limited b Water uali Standards: The wafer quality assessment in Ap~pendix A contains the. evaluation of po utanrs [mite y water qua try Stan ar he mass balance equation shown in Section IV of Appendix A was used for pollutatnu to calculate the maximum allowable e((JJlIueni concentratwn, Mz that could be discharged without causing the water quality standard to 6e violated. A detailed discussion of the calculations for the maxzmum allowable effluent pollutant coryryncentrations jar fecal coliforppm, totes! residual chlorine, ammonia a(}n~d metals is provided in Section of the as pail of ihee alculations represent~he ca~ u[ated efeJlueni limits that would be proteetivenof water quality. dThe eiare also known as the water quality-based effluent limns (WQBELs). The Permits Unit evaluated the calculated WQBELs and has made a determinarion as to whether there is a reasonable poterztial for the facility discharge to cause ar contribute to an exceedance of a stream standard. 7f there is a reasonable potential for the discharge to contribute to an exceedance, effluent limits are zncluded in the permit. i. Fecal colt arm total residual chlorine and ammonia: For fecal co[iform and total residual chlorine, the previously iscusse imits are more stringent t an ca cu ate WQBELs and therefore are applicable. Thus, a reasonable potential analysis was not performed and no further discussion of these pollutants is provided. For ammonia, ancillary and/or additional treatment technologies are often employed to reduce the ammonia concentrations. A facility may currently discharge ammonia at low-level concentrations to meet e~~lIueni limitations and therefore their effluent discharge shows no reasonableppotential to cause or contribute to exceeiTances of instream standards. However, absent limitatzons, a facility may no lon er continue such pollutant reductions and therefore the discharge will have reasonable potential. For this reason, the Permits Unit performs a qualitative determination of reasonable potential for ammonia. For total ammonia, the assimilative capacities shown in Appendix A are much greater than levels achieved by current ,.o„r.no„r technnloev. Thus, total ammonia limitations are not imposed and no monitoring is required. ii. Metals - the assimilative capacides contaizied in Appendix A, e calculated WQBELs in the permit. The gguuideknes are outlined in the Division's document, Det~inai on the amount of The first step, determining the pollutants of concern, the permit writer, with the coo erasion of the permittee, must use best professzonalludgment to determine the pollutants of concern ("POC's'). PPOC's are pollutants that might be expected in the effluent. POC's may. be: •pollutants that have been detected in the effluent (throough comppliance monitoring, prionry pollutant mors`itortng~ optional monitoring, or other monitoring) in to lutants that are p~esetntnin with known sources; pollutants that are known to commonly occur in similar effluents; p P the influent or at other sampling points in the treatment or collection systems; pollutanu that are present in the bioso ids or other treatment residuals; other pollutants which, in the permit writer s best professionalludgment, may befound in the effluent. The permittee provided upstream and downstream data from the West Elk Mine, which represents lnstream quality before and after the dischargge((s11. This data was compared with additional ambient data provided in The water quality assessment (Appendix A, Tatr[e A-6), and compared wzth the W BELs to determine what the POC's were. Additionally, with the development of ELGs for the Western Alka~ine Coa! Minin Subcategory, there was a consideration of what potential pollutants were pollutants of concern. Whereby, it was determined that total iron was the only pollutant of corscern. For this treasonfarcomplian~e schedule is included inhhe permit~ee Part LA.B.)nto givelthe permittee an opportunity to assess their treatment system's capability of meeting these limitations, and design and construct additional treatment facilities, if they are deemed necessary. The permittee will be required io submit a Preliminary Report by December 31 2004, detailing their plan for bringing the discharge into compliance with the find! limitations that become ef~ective January 1 2007. Because the previous permit had no limitations for these metals, none will be applied during the intenm enod. The reallocated limitations will be used as the final limitation. This compliance schedule applies to Outfal[ 017A. Last Revised: 4/19/10x4