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' , ~ ''~ ~ PART I Perrrrit No. CO-0032638 Page No. 6 A. DEFINITION OF EFFLUENT LIMITATIONS 4. Burden of Proof Requirements The permittee has the burden of proof when seeking relief from settleable solids (SS) limitations, as applicable. Settleable solids aze primary limitations for outfalls 001, 004, and 007. Outfa11001 is eligible for relief; and outfalls 004 and 007 may be eligible, providing the exceedence is caused by precipitation. a) For rainfall, to waiye settleable solids limitations, it is necessary to prove that discharge occurred within 48 hours after precipitation greater than the 10-yeaz, 24-hour event has stopped. b) For snowmelt to waive settleable solids limitations, it is necessary to prove that dischazge occurred within 48 hours after pond inflow volume greater than the 10-yeaz, 24-hour event has stopped. To claim an exemption in the event of a precipitation event or snowmelt, the permittee shall submit adequate proof as an attachment to the Dischazge Monitoring Report (DMR) for the appropriate period. The peratittee should endeavor to meet the primary limitations whenever possible. Relief may be granted for each dischazge occurrence only when necessary and shall not be granted when the permittee has control over the dischazge. The permittee will need to show that exceedence of the applicable limitations were caused by precipitaflon and no other source and that the dischazge was beyond their control. The Division shall determine the adequacy of proof. As part of this determination, the Division shall evaluate whether the pemuttee could have controlled the dischazge in such a manner that primary limitations could have been met. The permittee needs to demonstrate that surface runoff caused the exceedence of primary limitations. Additionally, the pemrittee shall certify that the pond system was properly designed, operated, and maintained before and during the dischazge. Manual dewatering of ponds that have no automatic dewatering devices must occur within 48 hours after event end as described in the above paragraphs to be eligible. All manual dewatering that occurs after 48 hours shall meet settleable solids limitations as applicable. 5. Post-Minute Areas Commencing at the time active mining has ceased and surface azeas have been returned to the required contour all applicable discharges maybe eligrble for limitations other than those specified in Part I.A.1. These post-mining limitations shall remain in effect until bond release. The permittee shall notify the Division upon cessation of active mining so that consideration of appropriate permit modifications can be made. B. MONITORING REQUIREMENTS 1. Frequency and Sample Tvve In order to obtain an indication of the probable compliance or noncompliance with the effluent limitations specified in Part LA.1, [he permittee shall monitor all effluent pazameters at the following frequencies. Such monitoring will begin immediately and last for the life of the permit unless otherwise noted. The results of such monitoring shall be reported on the Dischazge Monitoring Report form {See Part LE.). Also see Part LB.2. a. Outfa11001 Flow, MGD Weekly Lnstantaneous or Continuous Settleable Solids, mA/~. Monthly Grab Oil and Grease, mg/~. Weekly Visual pH, s.u. (Minimum-Maximum) Weekly In-Situ b. Outfalls 004 and 007 Flow (Effluent), MGD Weekly Instantaneous or Flow Ratio (Combined Effluent to Upstream Trout Creek) Weekly Calculation ISSUED: November 27, 2002 EFFECTIVE: January 1, 2003 EXPIRES: February 28, 2006