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<br />' the ouffalls for the mine dewatering boreholes (SDH-2, SDH-3 and SDH-5). The water from <br />SDH-2 is discharged at ouffall 024 and the water from SDH-3 and SDH-5 is discharged at ouffall <br />026. There is no discharge from SDH-1. The NPDES discharge quality parameters for the water <br />year are summarized in Table 2-4. <br />' Western Fuels-Utah started the whole effluent toxicity (WET) testing program beginning in the <br />fourth quarter of 1989. The mine water effluent was found to be toxic to the test species. <br />Accelerated testing was conducted but the toxicty to the species continued. <br />In a meeting with Colorado Water Quality Control Division (WQCD) staff on January 31, 1992, the <br />t WFU staff reiterated the biomonitoring events, and various measures taken to identity the toxicants <br />and to reduce the toxicity. WFU has taken the following steps to identity potential toxicants. <br />t <br /> <br />1 <br /> <br /> <br /> <br />t <br /> <br /> <br /> <br />1 <br />1 <br />• In the early stages of WET testing, the undisassociated HZS in the effluent was <br />deemed to be a potential toxicant However, a WE'f testing done by ENSR <br />Consulting in June 1990 after removing HZS by aeration still showed toxicity. This <br />result indicated that some other factor(s) also contributed to the toxicity. <br />• In September, 1990, ENSR Consulting was directed to conduct a 'toxicity <br />characterization' study to identify the primary cause of the toxicity. This study <br />considered pH effects, volatile organic carbon, metals chelation, aeration, total <br />dissolved solids (TDS) and ammonia. The lab determined high TDS (chlorides) as <br />the primary cause of the toxicity. However, a recent review shows no correlation <br />between LCD values and chloride or TDS levels. <br />WFU has taken the following measures to reduce toxicity of the effluent. <br />• On-site aeration structures were installed for HZS removal before discharging the <br />effluent. <br />• A pilot test was conducted to identify a flocculent for removing high levels of oil <br />and grease from the effluent. <br />13 <br /> <br />