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<br />Water leaving the mine as ventilation humidity represents a large quantity in the water <br />balance. The temperature of the exhaust ventilation air is almost constant, at 60° F. <br />1 No underground water is being pumped out since the fire episode. For the remaining life of <br />the D-Seam mine, the underground water will be left to fill the mined out areas. <br />2.2.1.6 NPDES Discharges At present, BME has 15 NPDES outfalls. Only one ouffall <br />(DP1) experienced discharge during this monitoring period. Ouffalls 024 and 026 at the sump <br />dewatering holes are not discharging since the January 31, 1996 underground fire episode. <br />' The NPDES discharge quality parameters for the water year are summarized in Table 2~. <br />They are all within the permit requirement. <br />2.2.1.7 Whole Effluent Toxicity (WET) Testing No WET testing was conducted during the <br />1998-1999 water year since there was no discharge of the underground water from the sump <br />' dewatering holes or from ouffall 004 (Pond PP2). A history of WET testing at Deserado Mine <br />follows below: <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 H,S 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 H,S 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 LCD values and chloride or TDS levels. <br />' BME took the following measures to reduce toxicity of the effluent. <br />ii <br />1 <br />