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Enviro -Chem Analytical, Inc. <br />2493 Hwy 6 &50 Unit 7 <br />Grand Junction, CO 81505 <br />C. <br />Effluent Toxicity Results for Ceriodaphnia <br />Chronic Toxicity Testing <br />OXBOW — July 2013 <br />2 Species <br />Table 5 summarizes the survival and reproduction results for the Ceriodaphnia <br />test. The chronic results show control organism survival and reproduction did not <br />meet minimum performance requirements. The MHW control exposure <br />supported 100% survival and mean reproduction of 28.3 young per original <br />female. The effluent concentrations all supported survivals of 100% or greater <br />except for the 100 %. The 100% showed total lethality at 24 hours. <br />Effluent concentrations of 6.25 %, 12.5 %, 25 %, and 50% supported Ceriodaphnia <br />mean young reproduction of 22.7 +/ -2.5, 26.3 +/ -3.2, 22.8 +/ -4.6, and 25.9 +/ -1.7, <br />respectively. Ceriodaphnia exposed to the 100% effluent concentration <br />supported a mean young reproduction of 0. <br />The survival NOEC was 52.6% effluent. The effluent reproductive IC25 was <br />50.3% effluent when compared to the control. This study fails to meet the <br />requirements for passing. <br />The lack of survival of the Ceriodaphnia at the 100% dilution is attributed to the <br />high alkalinity of the mine discharge water. High alkalinity is a known contributor <br />to the lethality of Ceriodaphnia. <br />7 <br />