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No underground water has been pumped out since January 1996. Water encountered in <br />the active areas of the mine is pumped to the mined out D seam area for storage. During <br />2009-10 36 gpm was pumped on average. About one six gallons of this is from pipe <br />leaks, wash down, etc. The remainder is from groundwater encountered during the <br />course of mining. <br />2.2.1.6 NPDES Discharges At present, BME has 11 NPDES outfalls. Outfall 001 <br />discharged twice during this monitoring period in response to intense rainfall events. All <br />discharges were in compliance with applicable discharge standards. Outfall 026 at the <br />sump dewatering holes has not discharged since the January 1996. The NPDES permit <br />was renewed effective October 1, 2007. <br />2.2.1.7 Whole Effluent Toxicity (WET) Testing No WET testing was conducted during <br />the water year since there was no discharge of the underground water from the sump <br />dewatering holes or from outfall 004 (Pond PP2). A history of WET testing at Deserado <br />Mine follows below: <br />BME started the whole effluent toxicity (WET) testing program beginning in the fourth <br />quarter of 1989. The mine water effluent was found to be toxic to the test species. <br />Accelerated 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, <br />1992, the BME staff reiterated the biomonitoring events, and various measures taken to <br />identify the toxicants and to reduce the toxicity. BME took the following steps to identify <br />potential toxicants. <br />• In the early stages of WET testing, the associated H2S in the effluent was <br />deemed to be a potential toxicant. However, a WET testing done by <br />ENSR Consulting in June 1990 after removing H2S by aeration still <br />showed toxicity. This result indicated that some other factor(s) also <br />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 <br />study considered pH effects, volatile organic carbon, metals chelation, <br />aeration, total dissolved solids (TDS) and ammonia. The lab determined <br />high TDS (chlorides) as the primary cause of the toxicity. However, a <br />recent review shows no correlation between LC50 values and chloride or <br />TDS levels. <br />BME took the following measures to reduce toxicity of the effluent. <br />10