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-4• ~;• Part I Page le of 19 Permit No. CO-0042562 B. MONITORING REQUIREMENTS 4. Frequency and Sample Type - Acute WET Testing (continued) The permittee shall conduct each acute WET test in general accordance with methods described in the Division guidance document entitled Guidelines for Conducting Whole Effluent Toxicity Tests. The permittee shall conduct an acute 48-hour WET teat using Ceriodaphnia sp., and an acute 96-hour WET test using fathead minnows. Acute tests will be replacement static tests of a single effluent grab sample. 5. Accelerated Testing If an individual toxicity test shows toxicity at any concentration less than or equal to the following Instream Waste Concentration (IWC) or if 50% species mortality in any dilution (including 100% effluent) is detected in any acute WET test conducted in accordance with this permit, the permittee shall notify the Division verbally within 24 hours and in writing (date of receipt) within S days of receipt of written lab test results and proceed with the following compliance schedule. Discharge Point IWC 001 and 002 (no mining) 37.0% 001 and 002 (mining) 46.1% Within 7 days of becoming aware of the toxicity, the permittee shall then begin weekly accelerated testing of the discharge with whichever species has proven (through the first instance of toxicity) to be the most sensitive. The permittee will continue such testing with one species until 2 consecutive weekly tests demonstrate acute toxicity, 2 consecutive weekly tests demonstrate no acute toxicity or a maximum of 5 weekly tests have been conducted. If no acute toxicity was demonstrated in the 2 consecutive weekly tests or in 3 of the 5 weekly tests, the permitee shall resume routine quarterly testing. In all other cases, a pattern of toxicity has been demonstrated and the permittee shall proceed with the Preliminary Toxicity Investigation. When a pattern of toxicity is demonstrated, the permittee shall orally notify the Division within 24 hours of becoming aware of the test result which demonstrates the pattern of toxicity and in writing within 5 days (da[e of receipt) after receiving the written lab test result which demonstrates the pattern of toxicity.