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PART I Page 5 Perini[ No. CO-0044776 •A. DEFINITION OF EFFLUENT LIMITATIONS 4. Burden of Proof Requirements The permittee has the burden of proof when requesting relief from total suspended solids (TSS), total iron and/or settleable solids limitations, as appropriate. The permittee should endeavor to mee[ the primary limitations whenever possible. Relief is not available for mine drainage alone, nor when dte majority of a discharge consists of mine drainage. For rainfall, to waive TSS and total iron limitations, it is necessary to demonsvate [hat discharge occurred within 48 hours after measurable precipitation has stopped. To waive settleable solids limitations, it is necessary to prove tha[ discharge occurred within 48 hours after precipitation greater than the 10-year, 24-hour even[ has stopped. For snowmelt, to waive TSS and total iron limitations, it is necessary to demonstrate that discharge occurred within 48 hours after pond inflow has stopped. To waive settleable solids limitations, i[ is necessary to prove that discharge occurred within 48 hours after pond inflow volume greater than the 10-yeaz, 24-hour event has stopped. Should a precipitation event or snowmelt occur, [he permittee shall submit adequate proof in order for an exemption to be claimed. Weather station data should be submitted where appropriate. Documentation that the treatment facilities were properly operated and maintained prior to and during the storm event must be submitted with any request for relief. Additionally for outfall 002 the Rrmittee mutt demonstrate that the maiority of the discharge for which the exemption is claimed consists of surface runoff. Said proof shall be submitted as an attachment to the Discharge Monitoring Repot[ (DMR) for the appropriate period. The Division shall determine the adequacy of proof. As part of this de[ermination, the Division shall evaluate whether the permittee could have controlled the discharge in such a manner [hat primary limitations could have been met, whether proper sediment storage levels were maintained and the ponds had sufficient water and sedimen[ capacity for the storm event plus other relevant factors. All manual pond dewatering must meet TSS and total iron limitations unless previous approval has been granted for ponds that have t~ other method of dewatering. For ponds with automatic dewatering structures, only discharges through these strucmres are eligible for [he exemption. 5. Post-Mining Areas In conformance with 40 CFR 434.50, commencing a[ the [ime active mining has ceased and all surface azeas served by a sedimentation pond have been returned to the required contour and revegetation has commenced, applicable discharges may be eligible for limitations other than [hose specified in Pan I.A.I. In most cases, these pos[-mining limitations shall remain in effect until bond release. The permittee shall notify dte Division at the appropriate time so that consideration of permit modifications can be made. Prior to notification and subsequent permit modifica[ion, active mining limitations will apply regardless of actual mine stains. 6. Whole Effluent Toeicity Testinp,~eauirements (Acutel - OutfaB 002 a. Testingand Reporting Requirements WET [esting shall be required whenever [he discharge contains any flow from mine drainage and/or spoils spring sources. WET [esting is not required when a discharge consists entirely of surface runoff. If discharge from outfall 002 contains mine drainage at any time during the appropriate monitoring Crequency period, WET testing is required during that period. Tests shall be done at the frequency listed in Part I.B.I. Test results shall be reported along with the Discharge Monitoring Report (DMR) submitted for the reporting period during which the sample was taken, (i.e., WET testing results for the first calendar quatter ending March 31 shall be reported with the DMR due April 28.) The results shall be submitted on the Acute Toxicity Tes[ repott forth, available • from the Division. Copies of these reports are to be submitted to both the Division and EPA along with the DMR. ~q Amendment No. 1 Issued .1lJN 2 8~0~~ Effective