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PART I Page No. 8 b_ Permit No. CO-0000132 A. DEFINIITON OF EFFLUENT LII~IITATIONS 4. Post-Minina Areas Commencing at the time active mining has ceased and surface azeas have been returned to the required contour all applicable discharges may be eligible 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. 5. Whole Effluent Toxicity Testine Requirements (Chronic) - Outfall 015 (a) Testine and Reportine Requirements Tests shall be done at the frequency listed in Part I.B.1.(cl Test results shall be reported on the Dischazge Monitoring Report (DMR) submitted for the reporting period during which the sample was taken. (i.e., WET [esting 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 Chronic Toxicity Test report form, available from the Division. Copies of these reports aze to be submitted to both the Division and EPA along with the DMR. The permittee shall conduct each chronic WET test in general accordance with methods described Short Tetm Methods for Estimative the Chronic Toxicity of Effluents and Receivine Waters to Freshwater Organisms, EPA/600/4-89/001 or the most current edition, except as modified by the mos[ current Division guidance document entitled Guidelines for Coaductine Whole Effluent Toxicity Tests. The petmittee shall conduct such [esu using fathead minnows. (b) Failure of Test and Division Notification A chronic WET test is failed whenever 1) there is a statistically significant difference in lethality between the control and any effluent concentration less than or equal to the ivstream waste concentration ("IWC") and, 2) the ICu, which represents an estimate of dte effluent concentration at which 25% of the [est organisms demonstrate inhibition as reflected by lethality, is at any effluent concentra[ion less than or equal to the IWC. The IWC for this permit has been determined to be 100%. The permittee must provide written notification of the failure of a WET test to the Division, along with a statement as to whether a Preliminary Toxicity Investigation ("PTI")/Toxicity Identification Evaluation ("TIE") or accelerated testing is being performed (see Part I.B.S.(c)). Notification must be received by the Division within 21 calendar days of the demonstration of chronic WET in the routine required test. "Demonsvation" for the purposes of Parts I.A.S.(b), (c), and (e). means no later than the las[ day of the laboratory test. (c) Automatic Compliance Schedule Upon Failure of Test If a routine chronic WET test is failed, even though monitoring only is required, the following automatic compliance schedule shall apply. As pan of this the permittee shall either: i. proceed to conduct the PTI/TIE investigation as described in Pan I.A.S.(d), or ii. conduct accelerated testing using the single species found to be more sensitive. If accelerated testing is being performed, the permittee shag provide written notification of the results within 14 calevdaz days of completion of the "Pattern of Toxicity"/"No Toxicity" demotstration. Testing will be at least once every two weeks for up to five tests until; 1) two consecutive tests fail or three of five tests fail, in which case a pattern of toxicity has been demonstrated or 2) two wnsecutive tests pass or three of five tests pass, in which case no pattern of toxicity has been found. See Part I.C. for Defmitions. Amendment No. 1 Issued APRII. 17 1997 Effective JUN 1 1997 Amendment No. 2 Issued DEC 28 1998 Effective FEB 1 1999 Amendment No. 5 Issued Effective ItNB, N"~vvlr 1". 19Y