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LTA COMMERCIAL TESTING & ENGINEERINGCO. <br />SiXCE tBCB~ <br />METHODS <br />A two species acute bioassay was conducted with effluent from the West Fork of Sylvester <br />Gulch, outfail 017. An effluent grab sample was collected on April 3, 2002, stored on ice, and <br />delivered to Commercial Testing and Engineering, Co. (CT&E) on the following day. The <br />effluent sample was received at a temperature of 9.0 ° C and assigned CT&E sample tracking <br />number 072-1509-001. The bioassay was initiated approximately 30 hours after sample <br />collection. <br />Testing was conducted in accordance with the most recent protocols specified by the Water <br />Quality Control Division of the Colorado Department of Health (1998), outlined in Table 1. <br />Basic characteristics ofthe efrluent and dilutions were measured as follows: <br />Characteristic Method/E ui ment EPA Method <br />Alkalinity <br />Ammonia <br />Chlorine, Total Residual <br />Conductivity <br />Dissolved Oxygen <br />Hardness <br />pH <br />Temperature <br />Titrimetric (APHA', 1989) <br />Lachat Anfilysis Method <br />LaMotte STC-CI Colorimeter <br />Orion Model 160 Cond. Meter <br />Orion Mode1850 DO Meter <br />Titrimetric (APHA, 1989) <br />Fisher Mode1925 pH Meter <br />IVISTz calibrated thermometer <br />EPA 310.1 & 130.2 <br />EPA 350.1 <br />EPA accepted <br />EPA 120.1 <br />EPA 360.1 <br />EPA 310.1 & 130.2 <br />EPA 150.1 <br />EPA accepted <br />The tests exposed daphnids, Daphnia magna, to five concentrations of effluent, 100%, 75%, <br />50%, 25%, and 1.9%, prepazed using reconstituted laboratory water at 205 mg/L CaC03. <br />Additionally, the tests exposed fathead minnows, Pimephales promelas, to five concentrations of <br />effluent, 100%, 75%, 50%, 25%, and 1.9%, prepared using reconstituted laboratory water at 100 <br />mg/L CaC03. Control replicates were exposed to 100% laboratory water. <br />The Probit and Binomial methods determined the LCso's3, where applicable. Significant <br />differences in mortality were analyzed using Steel's Many-One Rank tests. <br />' American Public Health Association <br />2 National Institute of Standards and Technology <br />3 Lethal ConcenUationso - an estimate of [he concentration lethal to 50% of the organisms in the time prescribed by <br />the test <br />