2009-02-26_REPORT - C1994082 (11)

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0 Sage Creek - Site YSSF3. This site exists on Sage Creek upstream of all potential Yoast mine discharges. This year, flow was observed in September for the first time since 1999. It displays a decreasing TDS trend. - NPDESI2. Mining in this basin began in 2000. Reconstruction of the water augmentation Pond Y1 (Site YSSF2) was completed on September 13, 1999. It is now referred to as Pond 012 (NPDESI2) . This pond began to flow again (after reconstruction) in April 2000. Flow at this pond is continuous. The average flow value for this year was 0.355 cfs, which was over four times the historic (2000-2008) average for Pond 012, 0.085 cfs, and was over two times the Pond Y1's historic (1991-1999) flow value, 0.129 cfs. A statistical summary of baseline chemistry data from Site YSSF2 (Yl outflow) and YSS3 (Y1 inflow) is provided in Appendix D1. NPDESI2 exhibits a stable TDS trend (SF=0.5). An old slide north of Pond 012 moved again this year, most likely a result of a very high snowpack runoff. An additional pond, 012A, was constructed this year to compensate for the lost capacity in Pond 012. - NPDESI3. Construction of this pond was completed in December 2003. It first began discharging on March 14, 2005. This year, this pond started flowing in January and stopped flowing in June. Average flow this year was 0.015 cfs, which was 36% greater than the historic (2005-2008) average value, 0.011 cfs. The TDS trend is increasing. - NPDESI4. Construction of this pond was completed in September 2001. It discharged for the first time on April 4, 2006. This year, this pond started flowing in April and stopped flowing in June. The average flow this year was 0.044 cfs, which was 100% greater than the historic (2006- 2008) average value, 0.022 cfs. TDS values are increasing, but the peak value is only 720 mg/1. Site YSS2. This site exists on Sage Creek below all potential Yoast Mine discharges. Monitoring at this site was resumed in 1998 after the 9