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Client: Mountain Coal Company CO - 0038766 SCG Project No.: 305112 <br />Site: West Elk Mine 017 <br />in USEPA' and the Colorado Department of Public Health and Environment". The <br />Daphnia magna tests were conducted over a 48-hour period, while the fish were exposed for 96- <br />hours, Exposure concentrations included 0%(control), 1.9%, 12.5%, 25%, 50% and 100% <br />effluent mixtures. Moderately hard laboratory reconstituted water was used as the dilution water <br />and control for the tests. Reconstituted water is prepazed by adding sodium bicazbonate, calcium <br />sulfate, magnesium sulfate and potassium chloride to deionized water. <br />A total of 20 organisms at each concentration were used for the Daphnia magna tests. <br />Daphnia magna were exposed in 30 ml plastic disposable beakers, each of which contained 15 <br />ml of the effluent mixture. Fathead minnow tests were performed in 250 ml plastic cups <br />containing 200 ml of test medium. Ten fish were used in each of the four replicates for a total of <br />40 fish per test concentration. <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 stock solution was then <br />returned to its original state by bringing the alkalinity back to that of the original effluent. <br />Laboratory grade NaHC03 (sodium bicarbonate) was added in order to raise the alkalinity. <br />These reconstituted samples were then run in acute 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 source of <br />toxicity. 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 />The SeaCrest Group 6 <br />