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METHODS <br />A two species acute bioassay was conducted on effluent taken from <br />Bear Coal Company. A grab sample from outfall 001 was collected on <br />December 16, 1997, delivered to Commercial Testing and Engineering <br />(CT&E) on December 18, 1997, and assigned CT&E number 72-373410. <br />The test was initiated approximately 50 hours after sample <br />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 (1993), outlined in Table 1. <br />The chemical characteristics of the effluent and dilution water <br />measured include pH, ammonia, residual chlorine, alkalinity, <br />hardness, dissolved oxygen, and conductivity. The pH was measured <br />using a Fisher Scientific model 925 pH meter (EPA method 150.1) and <br />ammonia was determined with an Orion 901 ionalyzer (EPA method <br />350.3). Total residual chlorine was measured using a LaMotte model <br />STC-C1 colorimeter (EPA accepted). Alkalinity and hardness were <br />determined by titrimetric methods specified by the American Public <br />Health Association, 1989, (EPA methods 310.1 and 130.2). Dissolved <br />oxygen was measured with an Orion model 850 oxygen meter (EPA <br />method 360.1) and conductivity was determined with an Orion Model <br />160 conductivity meter (EPA method 120.1). <br />The tests exposed cladocerans, Ceriodaohnia dubia, and fathead <br />minnow, Pimephales oromelas, to five concentrations of effluent, <br />100°s, 75°s, 50%, 25°s, and 1.7°s, prepared using laboratory water <br />reconstituted to 120 mg/L CaCO~. <br />Steel's Many-One Rank tests were used to determine if any <br />statistically significant difference in mortality. <br />LCSO's were calculated with the Probit Method where applicable. <br />-2- <br />COMMERCIALTESTING & EN GIN EEgING CO. <br />F-A66 Lt~ <br />Ori final Waterm ~rketl For Yoor Proleclion ~~ <br />