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<br />METHODS <br />An effluent grab sample from Somerset Mining was collected on <br />October 6, 1992, and received at Commercial Testing and Engineering <br />(CT&E) approximately 24 hours later where it was assigned CT&E <br />number 169760. Discharge receiving water from the Gunnison River <br />was also collected and delivered on the same dates. The test was <br />initiated approximately 24 hours after collection. <br />Testing was conducted in accordance with the most recent protocols <br />specified by the Water Quality Control Division of the Colorado <br />Department of Health, (2), as outlined in Table 1 and, with <br />additional guidance from the Environmental Protection Agency's <br />Methods for Aquatic Toxicity Identification Evaluations, Phase 1 <br />Toxicity Characterization Procedures (3). <br />The chemical characteristics of the effluent sample and receiving <br />- water were measured. The pH, dissolved oxygen, alkalinity, <br />hardness, ammonia and residual chlorine were determined as follows. <br />The pH was measured using a Fisher Scientific model 910 pH meter <br />and ammonia was measured using a LaMotte ammonia nitrogen test kit <br />and comparator. Total residual chlorine was measured using a <br />LaMotte model STC-C1 colorimeter. Alkalinity and hardness were <br />determined by titrimetric methods specified by the American Public <br />Health Association (1989). Dissolved oxygen was measured with a YSI <br />model 54A oxygen meter. <br />The test exposed the cladoceran, Cerioda~hnia dubia, to 1000 <br />effluent samples with alkalinity adjustments. Two hundred and <br />twenty microliters of 9, 18, 27 and 36 normality sulfuric acid was <br />added to individual beakers which contained 400 ml of 100°s <br />effluent. This resulted in effluent samples with alkalinities of <br />1110 mg/L, 650 mg/L, 95 mg/L and <5.0 mg/L respectively. <br />-2- <br />COMMERCIAL TESTING & ENGINEERING CO. <br />coal Coot/ Watermarked <br />=or Vour Pro~en.an <br />,0 <br />