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9.0 TRACER TESTNOTEXPECTED TO IMPA CTSTREAM ENVIRONMENT <br /> Davis et al. (1985, p. 93) state that "the concentrations of ionic solutions typically <br /> used in field tracer tests generally pose no measurable environmental or health <br /> effects". Cohen and Stubblefield (1991) report the values of acute and chronic <br /> toxicity for various freshwater aquatic species. The most sensitive species they <br /> studied was Ceriodaphnia dubia which showed an acute LC50 of 3,470 mg/1 of Br-, <br /> but a chronic value of only 1 .6 mg/I Br. <br /> The recommended average bromide concentration in the water-filled mine workings <br /> is 1 ppm. This is the same as the criterion for water quality recommended by Canton <br /> et al. (1983, cited in Cohen and Stubblefield). However, the bromide solution will be <br /> greatly diluted upon reaching the surface creeks and should not pose a problem to <br /> aquatic life in surface streams. <br /> 1AADMIN\WP\DIANE\BR0MIDE.RPT 8 <br /> HIl HYDRO-SEARCHAG A Tetra Tech Company <br />