APPENDIX I Toxicity Identification Evaluation Reports for Chollas ...

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Toxicity Identification Evaluation of Chollas Creek Stormwater using Hyalella azteca Results August 2006 4.1.3 Results of Special Testing Performed on November 11, 2005 Sample On November 11, 2005 a water sample was collected from Chollas Creek; however, there was not enough rain to consider this sampling event a storm event. Thus, there was not a large enough volume of stormwater to perform the standard toxicity tests using Hyalella azteca, Selenastrum capricornutum, and Ceriodaphnia dubia and to perform complete TIEs, as done in October. However, using the collected water, some TIE manipulations were performed using H. azteca as the test organism. The results of these tests are presented in Table 4. Table 4. Percent Survival of Hyalella azteca in Special Tests performed on the Chollas Creek Stormwater Sample Collected on November 11, 2005 Test Control (Blank) – Dilution Water Stormwater Dilution 50% 75% Stormwater Stormwater 100% Stormwater NOEC LC 50 Baseline (Glass) 80 86.7 66.7 40 75 98.44 Baseline (Plastic) 93.3 100 100 80 100 >100 PBO - 0.025 mg/L (Glass) 73.3 26.7 0 0
Toxicity Identification Evaluation of Chollas Creek Stormwater using Hyalella azteca Results August 2006 The Plastic 0.025 mg/L PBO treatment led to increased toxicity in the 100 percent sample concentration (33.3% survival) relative to toxicity in the unmanipulated Plastic Baseline test (80% survival in the 100 percent sample concentration). The NOEC was 100%, and the LC 50 was 70.8%. The Plastic 0.050 mg/L PBO treatment led to increased toxicity in the 100 percent sample concentration (0% survival), relative to toxicity in the unmanipulated Plastic Baseline test (80% survival in the 100 percent sample concentration). The NOEC was less than 50%, and the LC 50 was 36.1%. Survival in the Plastic 0.025 mg/L PBO treatment blank was 66.7% and survival in the Plastic 0.050 mg/L treatment blank was 86.7%. A copper sulfate reference toxicant was tested at nominal concentrations of 62.5, 125, 250, 500 and 1000 µg Cu 2+ /L. The calculated 96-hour LC 50 (189.41 µg Cu 2+ /L) was within two standard deviations of the laboratory mean (365.19 µg Cu 2+ /L) at the time of testing. This indicates that the sensitivity of H. azteca used in this evaluation fell within the normal range. 4.1.4 Summary of Specialized Testing Performed on November 11, 2005 Sample Results from the specialized tests performed on the Chollas Creek stormwater sample collected in November provided additional evidence that pyrethroids were a likely causative agent. In the baseline test, the higher toxicity in the glass test chambers relative to the plastic test chambers suggests that the causative agent had adsorbed to the plastic, thus leading to a reduced toxicity to organisms in the plastic test chambers. In addition, not only did PBO potentiate the toxicity, further indicating that the causative agent was pyrethroid-like chemicals, but there was also higher toxicity in the PBO treatments using glass containers relative to those treatments in which plastic was used. These results indicate that the causative agents have similar physicochemical properties to those of pyrethroids; the chemicals causing toxicity adsorbed to plastic, and their toxicity to H. azteca was potentiated by PBO. 4.1.5 Results of Phase I TIE Performed on January 2, 2006 Sample Results for the TIE performed on the January 2, 2006 sample are summarized in Table 5. In the Baseline test, toxicity of H. azteca exposed to the 100 percent sample concentration (53.3% survival) was slightly lower than in the initial toxicity test (25% survival) started on January 2, 2006. The NOEC was 100%, and the LC 50 was greater than 100%. Survival in the dilution water control was 86.7%. The 0.8 mg/L EDTA manipulation did not reduce toxicity in the 100 percent sample concentration (40% survival) relative to toxicity in the unmanipulated Baseline test (53.3% survival in the 100 percent sample concentration). Survival in the 0.8 mg/L EDTA treatment blank was 93.3%. Higher concentrations of EDTA (3 mg/L) used as part of this manipulation, also did not reduce toxicity in the 100 percent sample concentration (26.7% survival). Survival in the 3 mg/L EDTA treatment blank was 86.7%. These results indicated that metals were likely not responsible for the observed toxicity. The 10 mg/L sodium thiosulfate (STS) manipulation did not reduce toxicity in the 100 percent sample concentration (46.7% survival) relative to toxicity in the unmanipulated Baseline test (53.3% survival in the 100 percent sample concentration). Survival in the 10 mg/L STS treatment blank was 86.7%. A higher concentration of STS (25 mg/L) was also used in this manipulation; however, this concentration of STS caused toxicity in the dilution water control (60% survival), indicating that higher concentrations of STS are not appropriate for TIEs with H. azteca. Weston Solutions, Inc. 18
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