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LTA COMMERCIALTESTING & ENGINEERINGCO. <br />since .sae. <br />t'~) METHODS <br />A two species acute bioassay was conducted with effluent from New Horizon Mine, outfall 007. <br />An effluent grab sample was collected on July 10, 2002, stored on ice, and delivered to <br />Commercial Testing and Engineering, Co. (CT&E) on the following day. The effluent sample <br />was received at a temperature of 9.0 ° C and assigned CT&E sample tracking number 072-2744- <br />001. The bioassay was initiated approximately 24.5 hours after sample 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 (] 998), outlined in Table I . <br />Basic characteristics of the effluent and dilutions were measured as follows: <br />Characteristic Method/Bquipment 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 />Colorimetric Analysis Method <br />LaMotte STC-Cl Colorimeter <br />Orion Model 160 Cond. Meter <br />Orion Model 850 DO Meter <br />Titrimetric (APHA, 1989) <br />Fisher Model 925 pH Meter <br />NISTZ calibrated thermometer <br />EPA 310.1 & 130.2 <br />EPA 350.3 <br />EPA accepted <br />EPA 120.1 <br />EPA 360.1 <br />EPA 310.1 & 130.2 <br />EPA 150.] <br />EPA accepted <br />The tests exposed daphnids, Daphnia magna, to five concentrations of effluent, 100%, 75%, <br />50%, 25%, and 12.5%, prepared using reconstituted laboratory water at 225 mg/L CaCOs. <br />Additionally, the tests exposed fathead minnows, Pimephales promelas, to five concentrations of <br />effluent, 100%, 75%, 50%, 25%, and 12.5%, prepazed using reconstituted laboratory water at <br />110 mg/L CaC03. Control replicates were exposed to 100% laboratory water. <br />The Probit and Binomial methods determined the LCso's', where applicable. Significant <br />differences in mortality were analyzed using Steel's Many-One Rank tests. <br />American Public Health Association <br />s National Institute of Standards and Technology <br />3 Lethal Concenva[ion~ - an estimate of the concentration lethal to 50%of [he organisms in the time prescribed by <br />the test <br />6S <br />X26 <br />