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PART I Page 6 Permit No. CO-0044776 A. DEFINITION OF EFFLUENT LIMITATIONS 6. Wbole Effluent To~city Testig Requirements (Acute! - OutfaL 002 fcontinnnai The permittee shall conduct an acute 48-hour WET test using Ceriodan pia sp., and an acute 96-hour WET test 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 Meacuring„lhe Acute Tonicity of Fffluen[c and Receiving Wat tc to Fre hwat rand Marin O[ganicros, EPA/600/4-90/027 or the most current edition, except as modified by the most Curren[ Division guidance document entitled ,uideline for ondu tine Whale Effluent Tonicity Tesrc. b. Failure of Test and Division Notification An 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 ("PTT")!Toxicity Identification Evaluation ("TIE") investigation or accelerated testing is being performed (see nett section). 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 I.A.4.b., c., d. and f. means no later than the last da of the laboratory test. c. Automatic Compliance Schedule Upon Faiure of Test If a routine acute WET test is failed, the following automatic compliance schedule shall apply. As part 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 permittee shall provide written notification of the results within 14 calendar days of completion of the "Pattern of Toxicity"/"No Tosicity" 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 tonicity is found the tonicity 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 tonicity is not demonstrated but a significant level of erratic tonicity is found, the Division may require an increased frequency of routine monitoring or some other modifie approach. d. PTIlTIE The resLts of the PTI/TIE investigation are to be received by the DivLCion wit in 120 days of the demonstration of acute WET i the routine test as defined above or if accelerated testing is performed 60 and 90 day points of the PTI/TIE investigation. 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 [o the 120 day deadline. Such request must include a justification and supporring data for such an extension. The permittee may use the time for investigation [o conduct a I'TI or move directly into [he TIE. A PTI consis 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-__ incident, the TIE need no[ necessazily be conducted. If, however. WET is no[ identified or resolved during the PTI, the TIE muse be conducted within the allowed l20 day time frame. ~U?Sl 2 ~ ~,r.~ A Amendment No. !Issued Effective UG u 1 1999