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PARTI Page No. 5 Permit No. CO-0045080 •A. DEFINITION OF EFFLUENT LIMITATIONS 4. Whole Effluent Toxicity Testis; Re ~'remenL [Acute) - Outfallc 004 011 and 013 tcontin~o~l) The permittee 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 tesu of a single effluen[ grab sample. The permittee shall conduct each acute WET test in general accordance with methods described in Mer_hod_c for Measurine the Acute Tonicity of Effluents and Receivine Wa[ers to Freshwater and Marine Organi~mc, EPA/600/4-90/027 or the most current edition, except az modified by the most current Division guidance document entitled Guidelines far Conductine Whole Effluent Tonicity Tests. b. Failure of Test and Division Notification An acute WET test is failed whenever the LC~o, 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 sta[ement az to whether the Preliminary Tonicity Incident ("PTI")/Toxicity Identification Evaluation ("TIE") investigation or accelerated testing is being performed (see next section). Notification mtrst be received by the Division within 14 calendar days of the demonstration of acute WET in the routine required test. "Demonstration" for the purposes of Pans I.A.4.b., c., d. and f. means no Inter than the last day of the laboratory test. c. Automatic Compliance Schedule Lioon Failure of Te_ct If a routine acute WET test is failed, regardless of whether the limit is in effect, the following automatic compliance schedule shall apply. As pan of this the petatittee shall either: . i. proceed to conduct the PTI/TIE investigation az described in Pan 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 pet~ttittee shall provide written notification of the results within 14 calendar days of completion of the "Pattern of Toxicity"/"No Toxicity" demonstration. Testing will be at leazt 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 haz 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 toziciry is found, aPTI/TIE investigation is to be performed. If a pattern of toziciry 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 modified approach. d. PT]!T!E The c~ [rc of rhr PTTI'f'rF InyeStlg r' are rn he ~a~atved by the Division within 120 dayc of the demonstration of acute WET in the routine test ac defined above or if accelerated testing is performed the date the pattern of toxi i[y is demoncrrated A ct~tuc report is to be provided to the Division at the 30. 60 and 90 day points of the PTI/TIE investigation. The Division may extend the time frame for investigation where reazonable justification exists. A request for an extension must be made in writing and received prior to the 120 day deadline. Such request must include a justification and supposing data for such an extension. The permittee may use the time for investigation to conduct a PTI or move directly into the TIE. A PTI consists 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 WET incident, the TIE need not necessarily be conduced. If, however, WET is not identified or resolved during the PTI, the TIE must be • conducted within the allowed 120 day time frame. Any permittee that is required to conduct a PTl/TIE investigation shall do so in conformance with procedures identified in the following documents, or az subsequently updated: 1) Methodc for Aq~~atic Toxicity Identification rvaluations. Phase I Tonicity Characterization Procedures, EPA/600/6-91/003 Feb. 91 and 2) Methods for Aquatic Toni i Identification Evaluations. Phase iI Toxicity Identification Procedurs,, EPA/600/3-88/035 Feb. 1989. See Part I.C. for Definitions.