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Enviro -Chem Analytical, Inc. <br />2493 Hwy 6 &50 Unit 7 <br />Grand Junction, CO 81505 <br />Study Summary <br />Chronic Toxicity Testing <br />OXBOW — July 2013 <br />2 Species <br />A discharge sample collected from the Elk Creek Mine Outfall 015B, Somerset, <br />Colorado was evaluated for the presence of chronic toxicity to larval fathead <br />minnows (Pimephales promelas) and Ceriodaphnia dubia during July 23 -30, <br />2013. Moderately hard reconstituted water (MHW) prepared according to <br />USEPA guidelines was used as the diluent for the toxicity tests. <br />The effluent tests met minimum control organism performance requirements <br />defined by the USEPA. <br />The table below summarizes the results of the effluent tests. <br />Test Endpoint <br />Fathead Minnow <br />% Effluent <br />Ceriodaphnia dubia <br />96 Effluent <br />Survival NOEC <br />100 <br />52.6 <br />Survival LOEC <br />— <br />— <br />Growth /Reproduction <br />IC25 <br />>100 <br />50.3 <br />Organisms were purchased from Aquatic Biosystems located in Fort Collins, <br />Colorado. All reference toxicity test for both species were performed by them and <br />met minimum performance requirements defined by the USEPA and produces <br />IC25 values within the expected ranges. Organisms were or acceptable quality <br />and proper age upon arrival and beginning of test. <br />