2009-02-26_REPORT - C1994082 (11)

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This years TDS value at Wadge coal well YW30 was 6520 mg/1, which was over ten times the value observed in 2007, 590 mg/l. The PHC predicted value for this well is 2570 mg/1. More data from this well will be needed to determine if this year's value was an anomaly. Surface Water A summary of surface water sites is provided in Table 7. Stream monitoring occurs on Sage Creek at Sites YSSF3 and YSS2, and on Grassy Creek at Sites YSGF5 and YSG5. These surface water'sites are monitored triannually for flow and field parameters (pH, temperature, and electrical conductivity [EC]). NPDES Discharge Points 013 and 014 are monitored weekly for flow and pH. All five NPDES sites are monitored monthly for NPDES parameters and field parameters. Samples obtained at these stream and NPDES sites are analyzed for the surface water parameter list, Table 8, during April, May or June, and September. Spring sites are monitored in the spring season. The current surface water and spring monitoring program is presented in Table 15-9 of the Yoast Mine PAP. All surface water data collected during this reporting period are provided in Appendix D. Data for each site begins with a flow hydrograph of all historic data (plus an annual hydrograph for NPDES sites), followed by a listing of individual water quality and quantity data for the current water year, followed by remarks if present. This is followed by a TDS regression plot using the LOWESS method (see the Ground Water Quality section), and a listing of historic percent milliequivalent values for major ions and TDS values. A statistical report representing baseline (i.e., premining) data for each site downstream of mining (when available) is provided in Appendix D1. On this statistics report, "censored data" refers to analytical values that were below the detection limit, which were censored from the min/max/mean calculations. The time frame for baseline conditions is listed under "conditions specified" at the bottom of each page. 8