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City of San Marcos TPDES Permit No. WQOO10273002 demonstrate no significant sub-lethal effects. At that time, the permittee may apply for the testing frequency reduction. 3) If one or more ofthe first four consecutiye quarterly fathead minnow tests demonstrates significant lethal effects, the permittee shall continue quarterly testing until the permit is reissued. If a testing frequency reduction had been previously granted and a subsequent test demonstrates significant lethal effects, the permittee will resume a quarterly testing frequency for that species until the permit is reissued. 2. ReQuired Toxicity Testing Conditions a. . Test Acceptance - The permittee shall repeat any toxicity test, including the control and all effluent dilutions, which fail to meet the following criteria: 1) a control mean survival of 80% or greater; 2) a control mean number of water flea neonates per surviving adult of 15 or greater; 3) a control mean dry weight of surviving fathead minnow larvae of 0.25 mg or greater; 4) a control Coefficient of Variation percent (CV%) of 40 or less in between replicates for the young of surviving females in the water flea reproduction and survival test; and the growth and survival endpoints in the fathead minnow growth and survival test. 5) a critical dilution CV% of 40 or less for young of surviving females in the water flea reproduction and surviyal test; and the growth and survival endpoints for the fathead minnow growth and survival test. However, if statistically significant lethal or nonlethal effects are exhibited at the critical dilution, a CV% greater than 40 shall not invalidate the test. 6) a PMSD range of 13 - 47 for water flea reproduction; 7) a PMSD range of 12 - 30 for fathead minnow growth. b. Statistical futerpretation 1) For the water flea survival test, the statistical analyses used to determine if there is a significant differ- ence between the control and an effluent dilution shall be Fisher's Exact Test as described in the "Short- Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms, Fourth Edition" (EPA-821-R-02-013), or the most recent update thereof. 2) For the water flea reproduction test and the fathead minnow larval survival and growth tests, the statistical analyses used to determine if there is a significant difference between the control and an effluent dilution shall be in accordance with the methods described in the "Short-Term Methods for Estimating the Chronic Toxicity of Effiuents and Receiving Waters to Freshwater Organisms, Fourth Edition" (EPA-821-R-02-013), or the most recent update thereof. 3) The permittee is responsible for reviewing test concentration-response relationships to ensure that calculated test-results are interpreted and reported correctly. The EPA manual, "Method Guidance and Recommendation for Whole Effluent Toxicity (WET) Testing (40 CFR Part 136)" (EPA 82l-B-00-004) provides guidance on determining the validity oftest results. Page 25