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Client: M1luuntain Chat Compan}' CO -0038%66 SCG Project No.: 31/K302 <br />Site: Nest F:Ih D1inc 017 <br />in tJSEPA' and the Colorado Department of Public lfealth and Environment'. 1`he <br />Uup/tnict mnhma tests were conducted over a ~t8-hour period, while the fish were exposed tier 9G- <br />hours. Exposure concentrations included 0%(control), 1.4°.'0, 12.5%, 25%, 5(1% anJ 100°.0 <br />effluent mixtures. Moderately hard laboratory reconstituted water was used as the dilution water <br />and control for the tests. Reconstituted water is prepared by adding sodium bicarbonate, calcium <br />sulfate, magnesium sulfate and potassium chloride to dcionized water. <br />A total of 2U organisms at each concentration were used for the Duphniu nufgnu tests. <br />Daphnru mag~ru 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 ol'tcsl medium. 'fen fish were used in each of the four replicates for a total of <br />40 fish per test concentration, <br />lxposure 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 />ternperature, pl l and dissoh'ed oxygen in each concentration, before and aRcr the water change. <br />Test Prnc•eeGcres jor Uihrled Acute Tests <br />Three additional acute tests were performed to re-conlirtn the potential for TDS as a <br />source of toxicity in the c111uent. `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. :1liyuots of the <br />original etllucnt wcrc 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 cflhtcnt. <br />[.aboratory grade \a1iC0, (sodium bicarbonate) was added in order to raise the alkalinity. <br />~i'hesc reconstituted samples wcrc then run in acute toxicity tests :u concentrations of 100%, <br />~0%, 25%, 12.5% and L9%. 'this has the effect of maintaining a constant alkalinity while <br />diluting other contaminants that a>uld be present in the original et7luent. In essence, if similar <br />toxicity is observ•cd 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 />Dutu Arrulyri.c <br />Data from the test(s) were analyzed on a personal computer. Where applicable. LC50's <br />were calculated using EPA's TOXDr1T A•tulti-Method Program according to the binomial, prohit <br />or moving average methods. <br />