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PART I Page 6 Permit No. CO-0044776 A. DEFINITION OF EFFLUENT LIMITATIONS 6. Whole .ffluent Toxi ity Te 'n~Reauirementc (Acttel - OLtfaLl 002 (contLUedl The permittee shall conduct an acute 48-hour WET test using Ceriodaohnia sp., and an acute 96-hour WET using fathead minnows. Acute tests will be replacement static tests of a single effluent grab sample. The permittee. shall.conduct each acute: WET test in general accordance with methods described in Methods for EPA/600/4-90/027 or the most current edition, except as modified by the most current Division guidance document entitled Guidelines for Conducting Whole Effluent Toxicirv Tests. b. Failure of Test and Division Notification Aa acute WET test is failed whenever the LCso, 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 Idendficatiot: Evaluation ("TIE") investigation or accelerated testing is being performed (see nett section). Notification ma= 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 I.A.4.b., c., d, and f. means no later than the last dr of the laboratory test. c. Automatic Compliance Schedule Upyn Failure of Test If a routine acute WET test is failed, 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 Part I.A.4.d., or ii. conduct accelerated testing using the single species found to be more sensitive. If accelerated testing is being performed, the perttrittee shall provide written notification of the results within 14 calendar days of completion of the "Pattern oP Toxicity"/"No Tofficity" demonstration. 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 consecutive tests pass or three of five tests pass, in which case no pattern of toxicity has been found. If no pattern of toxicity is found the toxicity episode is considered to be ended and routine testing is to resume. If a pattern of tonicity is found, a PTUTIE investigation is to be performed. If a pattern of toxicity is not demonstrated but a significant level of erratic toxicity is found, the Division may require an increased frequency of routine monitoring or some other modifi[ approach. d. PTI/TIE The resultc.of the PTI/TIE in_vesripption are to be received by the Division within 120 davs of the I demonstration of acute WET L the routine test ac defined above or if accelerated testng is performed. the date the pattern of toACity is demonstrated A status report is to be provided to the Division at the 3a ~ 60 and 90 day points of the PTI/TIE investieation. The Division may extend the time frame for investigation. where reasonable justification exists. A request for an extension must be made in writing and received prior to I the 120 day deadline. Such request must include a justification and supporring data for such an extension. i The permittee may use the time for investigation to conduct a PTI or move directly inro the TIE. A PTI consist.' of a brief search for possible sources of WET, which might reveal causes of such toxicity and appropriate ;:. ' corrective actions more simply and cost effectively than a formal TIE. If the PTI allows resolution of the WE:_ 1 incident, the TIE need no[ necessazily be conducted. If, however. WET is not identified or resolved during the PTI, the TIE must be conducted within the allowed I20 day time frame. ~~l ~ 2 ~ '.fir.. AmendmentNo. l Issued Effective AUG u 1 1999