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PARTI Page No. 5 Permit No.: CO-0027146 b. For snowmelk to waive TSS and total iron limitations, it is necessary to prove that discharge occurred within 48 hours after pond inflow has stopped. Tn addition, to waive settleable solids limitations, it is necessary to prove that dischazge 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. Said proof shall be submitted as an attachment to the Dischazge Monitoring Report (DMR) for the appropriate period. The Division shall detemtine the adequacy of proof. As par[ of this detemtination, the Division shall evaluate whether the permittee could have controlled the dischazge in such a manner that primary limitations could have been me[. All manual dewatering of the pond(s) for outfalls 005, 007, 008, 009, O 10, 011, and 014 shall meet TSS and total iron limitations. All manual dewatering of the pond(s) for outfalls 012 and 013 shall meet settleable solids limitations. 3. Post-Mining Areas In confom~ance 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 dischazges may be eligible for post-mining limitations. 1n most cases, these post-mining limitations shall remain in effect until bond release. The pernrittee shall notify the Division at the appropriate time so that consideration of pernrit modifications can be made. Prior to notification and-subsequent permit modification, active mining limitations will apply regardless of actual mine status. 4. Acute WET Testin¢ Outfalls 001, 002, and 016 (Combined Outfall RSMW) a. Testing and Reporting Requirements Tests shall be done at the frequency listed in Part LB. Test results shall be reported along with the Discharge Monitoring Report (DMR) submitted for the end of the reporting period when the sample was taken. (i.e., WET testing results for the calendaz quarter ending Mazch 31 shall be reported with the DMR due Apri128, etc.) 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. The pernrittee shall conduct each acute VVET test in general accordance with methods described in "Methods forMeasuringthe Acute Toxicity ofEffluents and Receiving Waters to Freshwater and Marine Organisms" EPA/600/4-90/027 or its most current edition, except as modified by the most current Division guidance document entitled Guidelines for Conductine Whole Effluent Toxicity Tests. The petmittee shall conduct an acute 48-hour WET test using Ceriodaphnia sp., and an acute 96-hour WET test using fathead minnows. Acute tests will be replacement static tests of a single effluent grab sample. b. Failure of Test and Division Notification An acute WET testis failed whenever the LCs°, which represents an estimate of the effluent concentration which is lethal to 50% of the test organisms in the time period prescribed by the test, is found to be less than or equal to 100% effluent. The permittee must provide written notification of the failure of a WET test to the Division, along with a statement as to whether the Preliminary Toxicity Incident ("PTI")/Toxicity Identificafion Evaluation ("TIE") investigation or accelerated testing is being performed. Notification must be received by the Division within 14 calendaz days of the demonstration of acute WET in the routine required test "Demonstration" for the purposes of Parts b., c., d. and f. means no later than the last day of the laboratory test. J