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Mountain Coal CO-0038776 SCG Project Number: 304146 <br />Adjusted Dilutions <br />• (12.5% dilution) - An LC50 of 63.8% was produced in this test. Survival was 0% in the <br />100% concentration and ranged from 85-100% in the remaining concentrations. Control <br />survival was 100%. <br />• (25% dilution) - An LC50 of 74.0% was produced in this test. Survival was 5% in the <br />100% concentration and ranged from 90-100% in the remaining concentrations. Control <br />survival was 100%. <br />• (50% dilution) - An LC50 of 66.5% was produced in this test. Survival was 10% in the <br />100% concentration and ranged from 80-95% in the remaining concentrations. Control <br />survival was 100%. <br />Table 1-Survival and LC50 Calculations <br />SURVI~?AI;~TQTALS. OUT,OF20 -•.:'' <br />«~~ <br />_ `;Treated & ad'usfed effluents ' <br />Concentrat~oq.% _ <br />'Or final Effluent: ~. '12 5% r':- 25%: -. '=SO%. -! <br />Control 0 20 20 20 20 <br />1.9 20 19 20 20 <br />12.5 17 19 20 20 <br />25 16 I 19 18 20 <br />50 17 ; 16 20 17 <br />100 8 I 2 1 0 <br />`LC50 '- 86.6% 66.5% 74.0% 63.8% <br />" 95°/u Limits 0-50 50.0-100.0 50.0-100.0 50.0-100.0 <br />DISCUSSION <br />The Daphnia magna test of the original (non-diluted) effluent fails due to the creation of <br />an LC50 concentration of 86.6%. All additional dilutions of the effluent produced LCSOs at or <br />below the 100% concentration. ' <br />These results demonstrate that the dilution of the effluent samples did not significantly <br />reduce toxicity; therefore, it can be concluded that high alkalinity is probably the main source, if <br />not the only source, of toxicity to the Daphnia magna species in this particular effluent sample. <br />The SeaCrest Group, LLC 7 <br />