_GENERAL DOCUMENTS - C1981017 (288)

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PART I Page v Permit No. CO-0000396 ,. TERMS AND CONDITIONS 1. Effluent Limitations (continued) (d) Whole Effluent Toxicity - Chronic Lethality Limitation (outfalls 002 003 004, 005 016 019 026 and 029): Beginning immediately and lasting through April 30, 1999, there shall be no statistically significant difference in lethality (at the 95% confidence level) between the control and any effluent concentration less than or equal to 100% effluent. Such limitation shall apply as a daily maximum. 2. Burden of Proof Requirements The permittee has the burden of proof when seeking relief from total suspended solids (TSS), total iron and/or settleable solids (SS) limitations. Discharges from outfalls 002, 003, 004, 005, 019, 026 and 029 are not eligible for this exemption. Outfall 016 is eligible for relief from TSS and SS; however, the majority of the loading from any discharge has to consist of storm runoff for the relief to be available. The permittee will need to show that exceedence of the applicable limitations was caused by precipitation and not mine water, through a comparison of the loading from each source. The remaining permitted outfalls (001, 006, 008, 009, 010, 013, 014, 015, 017, 018, 020, 021, 022, 023, 025, 027 and 030) are eligible for relief from TSS, T. Iron and SS at all times since only surface runoff discharges are authorized from these outfalls. Relief may be granted for each discharge occurrence only when necessary and shall not be granted when the permittee has control over the discharge. The permittee should endeavor to meet the primary limitations whenever possible. a) For rainfall, to waive TSS and total iron limitations, it is necessary to prove that discharge 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. b) For snowmelt, to waive TSS and total iron limitations, it is necessary to prove that discharge occurred within 48 hours after pond inflow has stopped. In addition, 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. Should a precipitation event or snowmelt occur, the permittee shall submit adequate proof in order for an exemption to be claimed. Weather station data may be appropriate in making this demonstration. Said proof shall be submitted as an attachment to the Discharge Monitoring Report (DMR) for the appropriate period. The Division shall determine the adequacy of proof. As part of this determination, the Division shall evaluate whether the permittee could have controlled the discharge in such a manner that primary limitations could have been met. All manual dewatering of the ponds shall meet TSS and total iron limitations. 3. Post-Mining Areas Commencing at the time active mining has ceased and surface areas have been returned to the required contour and rc.� ,betation has begun, applicable discharges may be eligible for limitations other than those specified in Parts I.A.I. These post-mining limitations shall remain in effect until bond release. The pwinittce shall notify the Division at the appropriate time so that consideration of permit modifications can be made. 4. Salinity Parameters In order to obtain an indication of the quantity of Salinity being discharged from the site, the permittee shall monitor the wastewater effluent at the following frequency: Outfall Frequency Sample Type 001 Quarterly Grab See Part I.C. for Definitions. APR t 199E Amendment No. 1 Issued FE B 9 — I99&ffective