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Mountain Coal Company CO - 0038776 SCG Project No.: 304204 <br />Site: West Elk Mine <br />A total of 20 organisms at each concentration were used for the tests. Daphnia magna <br />were exposed in 30m1 plastic disposable beakers, each of which contained 15m1 of the effluent <br />mixture. <br />Exposure medium in each chamber was replaced every 24-hours and organisms surviving <br />at each concentration were counted and recorded. Routine measurements were made of <br />temperature, pH and dissolved oxygen in each concentration, before and after the water change. <br />Test Procedures for Diluted Acute Tests <br />Three additional acute tests were performed to re-confirm the potential for TDS as a <br />source of toxicity in the effluent. These tests were designed to indicate the presence of other <br />contaminants that could be present. <br />The tests were accomplished by making three reconstituted test solutions. Aliquots of the <br />original effluent were diluted to stocks of 50%, 25%, and 12.5%. Each of these stock solutions <br />was then returned to its original state by bringing the alkalinity back to that of the original <br />effluent. Laboratory grade NaHC03 (sodium bicazbonate) was added in order to raise the <br />alkalinity. These reconstituted samples were then run in toxicity tests at concentrations of 100%, <br />50%, 25%, 12.5% and 1.9%. This has the effect of maintaining a constant alkalinity while <br />diluting other contaminants that could be present in the original effluent. In essence, if similaz <br />toxicity is observed in all of the tests, then the alkalinity can be recognized as the cause of the <br />problem. If the toxicity decreases with the increasing dilution of the reconstituted samples, then <br />it can be assumed that some other toxicant is present. <br />Data Analysis <br />Data from the test(s) were analyzed on a personal computer. Where applicable, LC50's <br />were calculated using EPA's TOXDAT Multi-Method Program according to the binomial, probit <br />or moving average methods. <br />RESULTS <br />The data sheets for the acute tests are located in Appendix 2. Table 1 summarizes the <br />results of tests with the treated and untreated effluent. <br />Table 1. Survival and LC50 calculations for treated and untreated effluent. <br />The SeaCrest Group, LLC 6 <br />