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PART I Page No. 5 Permit No. CO-0044776 A. DEFINITION OF EFFLUENT LINIITATIONS 2. 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 petmittee should endeavor [o meet the primary limitations whenever possible. Relief is not available for mine drainage alone, nor when the majority of a discharge consists of mine drainage. For rainfall, to waive TSS and total iron limitations, it is necessary to demonstrate that discharge occurred within 48 hours after measurable precipitation has stopped. To waive settleable solids limitations, it is necessary [o 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 necessary to demonstrate that discharge occurred within 48 hours after potid inflow has stopped. To waive settleable solids limitations, it is necessary [o prove that discharge occurred within 48 hours after pond inflow volume greater than the 10-year, 24-hour event has stopped. Should a precipitation event or snowmelt occur, the pertnittee shall submit adequate proof in order for an exemption [o 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 permittee must demonstrate [hat the maiori[v of the discharge for which the exemption is claimed consists of surface runoff. Said proof shall be submitted as an attachment [o the Discharge Monitoring Repott (DMR) for the appropriate period. The Division shall determine the adequacy of proof. As part of this determination, the Division shall evaluate whether [he permittee could have controlled the discharge 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 sediment capacity for the storm event plus other relevant factors. All manual pond dewatering must meet TSS and total iron limitations uriless previous approval has bee^ granted for ponds that have no to her method of dewatering. For ponds with automatic dewatering structures, only discharges through these s[rucmres are eligible for the exemption. 3. Post-Mining Areas In conformance with 40 CFR 434.50, commencing at the time active mining has ceased and all surface areas 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 those specified in Part I.A.1. In most cases, these post-mining limitations shall remain in effect until bond release. The permittee shall notify the Division at the appropriate time so [hat consideration of permit modifications can be made. Prior to notification and subsequent permit modification, active mining limitations will apply regardless of actual mine slams. 4. Whole Effluent Toxicity Testing Requirements (Acutel - Outfall 002 a. Testing and Reporting 2Zequirements WET testing shall be required whenever the discharge contains any flow from mine drainage and/or spoils spring sources. WET testing is not required when a discharge consists entirely of surface runoff. If discharge from outfa0 002 contains mine drainage at any time during the appropriate monitoring frequency period, WET testing is required during that period. Tests shall be done at the frequency listed in Part I.B.1. 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 quarter ending March 31 shall be reported with the DMR due April 28.) The results shall be submitted on the Acute Toxicity Test report form, available from the Division. Copies of these reports are to be submitted to both the Division and EPA along with the DMR.