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Steve Royall NCPA CT-2 Discharge Characterization Page 3of6 January 22,2007 The bioassay results for influent and effluent indicate that some part of the impact to the growth of the fathead minnows is attributable to the NCPA influent. The influent No Observable Effect Concentration of 12.5% is lower than the corresponding value determined for the NCPA effluent (25-7c), indicating that first effects of toxicity were observed at a lower concentration of NCPA influent(12.5%) than NCPA effluent(where first effects were noted at a concentration of 25% NCPA effluent). In addition, the IC25 value of 59.9% for the NCPA influent indicates that 25c1c of the test population demonstrated inhibition of growth when reared in water consisting of 59.9% NCPA influent(WPCF effluent). PQLs Analyses for eight duality parameters used methods with a PQL slightly higher than the quantation limits recommended by Regional Water Quality Control Board, Region Five, in the revised 13267 List released December 2001. The differences in quantation are minimal, and the added cost of special analysis to achieve slightly lower limits is not justified by the limited data which might be gained. The eight parameters are shown in Table 3, below, along with the lab PQLs and the Criterion Quantation Limits recommended by the Regional Board in Sacramento. These analytes are flagged with the"a"flag in Table 1. Table 3—Quantation Limits Analyte Method CQL ' Influent PQL Effluent PQL 1.3 diclhloropropene 8260B 0.5 ul L NS I u Carbon tetrachloride 8260B 0.5 u IL 0.5 u L I u L Vinyl chloride 8260B 0.5 ugfL 0.5 uFZL I ug Antimony 200.7 5 u L 10 u szIL 10 u a L Beryllium 200.7 I u fL 5 u 5 u IL Lead 200.7 0.5 ugfL 10 u L 10 ugfL Heptachlor 8081 0.01 u L 0.05 u L 0.05 u Heptachlor epoxide 8081 0.01 u 0.05 ug/L 0.05 ugl Notes ' CQL: Criterion Quantation Limit. The quantation limits recommended by Regional Water Quality Control Board, Region Five, Revised 13267 Letter, December 2001. NS_ Not Sampled Water Conditioning Chemicals The Regional Board specified analysis for process chemicals referenced in NCPA's facsimile correspondence to the Regional Board dated April 5. HSe's understanding is that the NCPA facility uses sodium hypochlorite and sulfuric acid, which would be detected by other analyses already performed. In addition, HSe's understanding is that the following five proprietary compounds constitute the full list of proprietary process chemicals referenced in Attachment B to the regional Board's April 21 letter: ■ Nalco 71 D5 Plus Antifoam ■ Nalco 7396 Water Stabilization ■ Nalco 7346 Microbicide • Nalco 73199 ■ Nalco Trasar 23268