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L^~ COMMERCIAL TESTING & ENGINEERING CO. <br />DISCUSSION cont. <br /> <br /> <br /> <br /> <br />,~ <br /> <br /> <br /> <br />:~ <br />F.526 <br />• TDS may be indicated because there was greater sensitivity by C. dubia compared to fathead <br />minnows (APT 1998). Please note that this observation was made from prior bioassays. <br />• Conductivity exceeded 3,000 µmhosJcm at the LCso for C. dubia (USEPA 1992). <br />• The acid base ion exchange resin removed toxicity. This, combined with the previous <br />indicators, is an indication of TDS toxicity (USEPA 1992). <br />Based on the above toxicity evaluation and the analytical history of discharge site 001, the results <br />suggest that TDS ions are the constituents inhibiting Ceriodcaphnia dubia survival in the <br />quarterly, acute bioassays. <br />Furthermore, an ion balance program was utilized to see how the charge balance differed. The <br />analysis of the test solution indicated a % difference of -3.04. Usually a % difference that <br />exceeds t S.0 is considered an unbalanced charge and could indicate a potential problem. <br />However, this does not seem to be the case with effluent from Bear Coal Company. Please refer <br />to Appendix D for complete analysis. <br />8 <br />