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PART I Page No. 6 Permit No. CO-0044776 A. DEFINITION OF EFFLUENT LIMITATIONS 4. Whole Effluent Toxicity Testing Requirements fAcutel - Outfall 002 tcontinuedl The permittee shall conduct an acute 48-hour WET test using Cerioda~ 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 Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, EPA/600/4-90/027 or the most current edition, except as modified by the most current Division guidance document entitled Guidelines far Conducting Whole Effluent Toxicity 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 statement as to whether the Preliminary Toxicity Incident ("PTI")/Toxicity Identification Evaluation ("TIE") investigation or accelerated testing is being performed (see next section). Notification must 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 Parts I.A.4.b., c., d. and f. means no later than the last day of the laboratory test. c. Automatic Compliance Schedule Upon Failure of Test If a routine acute WET [es[ 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 Toxicity" demonstration. Testing will be a[ 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. [f no pattern of toxicity is found the [oxiciry episode is considered to be ended and routine testing is to resume. If a pattern of [oxiciry is found, aPTI/TIE investigation is to be performed. If a pattern of toxicity is not demonstrated but a signiftcant level of erratic toxicity is found, the Division may require an increased frequency of routine monitoring or some other modified approach. d. PTI/TIE The results of the PTI/TIE investigation are to be received by the Division within 120 days of the demonstration of acute WET in the routine test. as defamed above, or if accelerated testing is performed. the date the pattern of toxicity is demonstrated. A status 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 reasonable 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 supporting data for such an extension. The permittee may use [he time for investigation [o conduct a PTI or move directly into the TIE. APT[ 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 no[ necessarily be conducted. If, however, WET is not identified or resolved during the PT[, the TIE must be conducted within the allowed 120 day time frame.