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1 <br />' BME started the whole effluent toxicity (WET) testing program beginning in the fourth quarter <br />of 1989. The mine water effluent was found to be toxic to the test species. Accelerated <br />testing was conducted but the toxicity to the species continued. <br />In a meeting with Colorado Water Quality Control Division (WQCD) staff on January 31, 1992, <br />the BME staff reiterated the biomonitoring events, and various measures taken to identify the <br />' toxicants and to reduce the toxicity. BME took the following steps to identify potential <br />toxicants. <br />' In the early stages of WET testing, the associated HzS in the effluent was <br />deemed to be a potential toxicant. However, a WET testing done by ENSR <br />' Consulting in June 1990 after removing HzS by aeration still showed toxicity. <br />This 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 <br />(chlorides) as the primary cause of the toxicity. However, a recent review <br />' shows no correlation between LCs~ values and chloride or TDS levels. <br />' BME took the following measures to reduce toxicity of the effluent. <br />• On-site aeration structures were installed for HzS removal before discharging <br />' the effluent. <br />' A pilot test was conducted to identify a flocculent for removing high levels of oil <br />and grease from the effluent. <br />' The main water source of the mine was changed from the high TDS(>5000 <br />ppm) alluvial well water to a significantly lower TDS (500 ppm) surface lagoon. <br />' The raw water tank was thoroughly cleaned and disinfected to remove sludge <br />built up over years. This sludge was found to contain significantly high levels <br />' (1000 colonies/ml) of bacteria. <br />' An MSHA waiver was received to stop the use of Wendon Dustrol-10 <br />surfactant in the water spray at the longwall face. The surfactant has been <br />found to be lethal to fish life at 500 ppm. <br />9 <br />