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A88TRACT <br />Results of past acute bioassays indicate that effluent from outfall <br />011 at the Somerset Mining Company is acutely toxic to C. dubia. <br />Past investigative tests have indicated that toxicity was removed <br />by lowering the effluent pH prior to organism exposure. Based on <br />those test results and an "In-Stream" bio-assessment, the facility <br />was permitted test modification as part of their permit compliance <br />monitoring. However, the most recent modified Whole Effluent <br />Toxicity (WET) tests employing the pH adjustment was not successful <br />in removing alI the effluent toxicity to C. dubia. Therefore, as <br />mandated by the Colorado Department of Health, a modified Toxicity <br />Identification Evaluation (TIE) was conducted to identify possible <br />contaminates other than the Total Dissolved Solids (TDS) toxicity <br />(due to the increase in concentrations of sodium and bi-carbonates) <br />known to be present in the effluent, Results of the TIE tests and <br />their effect on the toxicant(s), and the indication of toxicity due <br />to dissolved solids is discussed. <br />COM MERCIALTESTING & EN GIN EE RING CO. <br />Fd68 L~~ <br />Original Watermarkeo For Your Protectron ,. <br />