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METHODS <br />Acute investigative bioassays were conducted on effluent collected <br />from outfall 011 at Somerset Mining Company. Grab samples were <br />collected on August 7, 1995, delivered to Commercial Testing and <br />Engineering (CT&E) on August 8, 1995, and assigned CT&E number 72- <br />312054. Testing began approximately 29 to 48 hours after sample <br />collection. <br />Testing was conducted with reference to the most recent protocols <br />specified by the Water Quality Control Division of the Colorado <br />Department of Health (1993), outlined in Table 1 and with reference <br />to "Methods for Aquatic Toxicity Identification Evaluations: Phase <br />I Toxicity Characterization Procedures", EPA-600/6-91/003, <br />February, 1991. <br />Chemical characteristics of the water samples were measured as <br />follows: the pH was measured using a Fisher Scientific 925 pH meter <br />(EPA method 150.1); ammonia was measured with an Orion 95-12 <br />ionalyzer (EPA 350.3); total residual chlorine was measured using <br />a LaMotte STC-C1 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 850 oxygen meter (EPA 360.1); and <br />conductivity was measured with a YSI 31 conductivity bridge (EPA <br />120.1). Total Dissolved Solids (TDS) were determined by EPA method <br />160.1. <br />Phase I Toxicity Characterization <br />The following tests were conducted in the Phase I Toxicity <br />Identification Evaluation: <br />Initial Toxicity Test - organisms were exposed to 0%, 1%, <br />25%, 50%, 75% and 100% effluent prepared using <br />reconstituted laboratory water at 125 mg/L CaC03. A total <br />of 20 organisms per concentration were exposed within 29 <br />hours of sample collection. <br />Baseline Test - Organisms were exposed to 0%, 12.5%, 50% <br />and 100% effluent prepared using reconstituted laboratory <br />water at 125 mg/L CaCO3. A total of 10 organisms per <br />concentration were exposed at 24 hours and 48 hours after <br />sample collection. The baseline test results are <br />compared to those Phase I characterization tests below <br />that were initiated concurrently. <br />Degradation Test - Toxicity degradation was determined <br />through observation of the above initial and baseline <br />toxicity test results. <br />3 <br />COMMERCIALTESTING & ENGIN EE RING CO. <br />F466 L~~ <br />Original Wetermerketl Far Your Protection ,.. <br />