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<br />INTRODUCTION <br />Biomonitoring provides an effective means to test multimedia effluents for toxicity. <br />Detection of such effects solely through chemical analyses are often difficult to accomplish. <br />Dischargers holding NPDES permits are required to perform both acute and, in some cases, <br />chronic biomonitoring tests as part of their permit requirements. The chronic tests measure <br />signficant differences in either reproduction (Ceriodaphnia) or growth (fathead minnows) between <br />control and exposed organisms. These tests are conducted over 7 days as opposed to the 48 <br />hr and 96 hr acute tests which measure mortalities. <br />In July 1998 acute biomonitoring tests were conducted on the 005, 006, and 010 <br />discharges of Peabody Coal's Seneca Mine. The tests were conducted with the freshwater <br />invertebrates, Ceriodaphnia dubia and Daphnia magna. The 005 discharge failed the test with <br />the Ceriodaphnia and was required to proceed to accelerated testing. This report details the <br />results of a PTI performed after an accelerated test conducted with the Ceriodaphnia dubia and <br />Daphnia magna showed toxicity in the Ceriodaphnia test but not in the Daphnia magna <br />test. TDS (Total Dissolved Solids) were the suspected toxicity agent. <br />MATERIALS AND METHODS <br />Sample Collection <br />A chemical analysis of the 005 discharge, taken on June 1, 1998, was faxed to the <br />SeaCrest lab on July 29, 1998. The effluent analysis was pertormed by ACZ Laboratories, Inc. <br />in Steamboat Springs, Colorado. A copy of the analysis is included in Appendix 1. <br />Test Procedures <br />The Gas Research Institute's Freshwater S7R (Salinity Toxicity Relationship) Model and <br />Computer Program was acquired from ENSR Consulting and Engineering in Ft. Collins, Colorado. <br />The quantities of the major ions analyzed were entered into the STR program to determine <br />whether the dissolved solids present could cause toxicity to the Ceriodaphnia. The ions used in <br />the analysis were Calcium, Magnesium, Potassium, Sodium, Chloride, Bicarbonate, and Sulfate. <br />Survival data were entered for the Ceriodaphnia and Daphnia magna quarterly test and <br />for the first accelerated test. These numbers were then evaluated against the predicted effects <br />from the major ion analysis. <br />Data Analysis <br />The data were analyzed on an IBM compatible 486 personal computer by the STR Model <br />and Computer Program. The program determined the LC50 % of solution for each species tested <br />and the predicted survival in the 100% effluent. <br />RESULTS <br />Ceriodaphnia Test <br />The STR analysis predicted that an LC50 concentration would be produced in a <br />Ceriodaphnia test with the 005 effluent. The 48 hour LC50 predicted by the model for the <br />Ceriodaphnia test was 70%. The actual LC50 created in the quarterly test was 95.5%. The <br />