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METHODS <br /> Single species acute bioassays were conducted with influent and <br /> effluent from the Rock Tunnel Ponds, outfall 016. Grab samples of <br /> influent and effluent were collected on June 17 and June 24, 1996, <br /> delivered to Commercial Testing and Engineering (CT&E) on June 17 <br /> and June 25, 1996 and assigned CT&E numbers 72-338475, 72-338473, <br /> 72-338878 and 72-338877, respectively. The tests were initiated <br /> approximately 25 hours after sample 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 /> Chemical characteristics of the effluent and dilution water were <br /> measured as follows: the pH was measured using a Fisher Scientific <br /> 925 pH meter (EPA method 150.1) ; ammonia was measured with an Orion <br /> 901 ionalyzer (EPA 350.3) ; total residual chlorine was measured <br /> using a LaMotte STC-Cl colorimeter (EPA approved) ; alkalinity and <br /> hardness were determined by methods specified by the American <br /> Public Health Association, 1989 (EPA 310. 1 and 130.2) ; dissolved <br /> oxygen was measured with an Orion model 850 oxygen meter (EPA <br /> 360.1) ; and conductivity was measured with a YSI 31 conductivity <br /> bridge (EPA 120. 1) . <br /> The tests exposed the Cladocerans Ceriodaphnia dubia to five <br /> concentrations of influent and effluent, 100%, 75%, 50%, 25%, and <br /> 12.5%, prepared using laboratory water reconstituted to =127 mg/L <br /> CaCO3. Control replicates were exposed to 100% laboratory water. <br /> LC50 values were determined with the Probit Method. Data was <br /> analyzed for significant mortality using Dunnett's and Steel's <br /> Many-One Rank test. <br /> -2- <br /> COMMERCIAL TESTING & ENGINEERING CO. <br /> F-466 <br /> Original Watermarked For Your Protection <br />