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Mountain Coal Company CO-0038776 SCG Project No.: 304181 <br />DISCUSSION <br />The Daphnia magna test of the regular (untreated) effluent fails due to the production of <br />an LC50 concentration of 86.6%. All additional dilutions of the effluent produced LC50 <br />concentrations below the 100% concentration. <br />These results demonstrate that the dilution of the effluent samples did not significantly <br />reduce toxicity; therefore, it can be deduced that high alkalinity is probably the main source, if <br />not the only source, of toxicity to the Daphnia magna species in this particulaz effluent sample. <br />REFERENCES <br />1. Hach Chemical Company. 2002. Hach Water Analysis Handbook. Hach Chemical <br />Company. Loveland, Colorado. 1260 pp. <br />2. APHA/AWWA/WEF. 1998. Standard Methods for the Examination of Water and <br />Wastewater. 20`s Edition. American Public Health Association. <br />3. USEPA 2002. Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters <br />to Freshwater and Marine Organisms. EPA-821-R-02-012. <br />4. Colorado Department of Public Health and Environment (CDPHE). 1998. Laboratory <br />Guidelines for Conducting Whole Effluent Toxicity Tests. Water Quality Control Division. <br />The SeaCrest Group, LLC 7 <br />