2011-04-29_REPORT - C1981044 (2)

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C] The field parameter data for the three Middle Sandstone wells (TR-4, TR-7A, 81-01) was reviewed. Water quality data are summarized in Tables 7 through 12. Plots of field conductivity for these Middle Sandstone Wells are presented in Figure 14. The conductivity measurements recorded at well TR-7A remain stabile as compared to historic values. However, it has Middle Sandstone wells TR-4 and 81-01 continue to have elevated conductivity values since monitoring was re-initiated in 2006. BTU-EC will continue to monitor these sites in order to ascertain a possible reason for this effect. In 2007, BTU-EC verified that the contractor (Miller Water Monitoring Service) was sampling the appropriate well. Wells TR-7A and TR-4 have historically indicated a slight reduction in concentrations of major ions over time. Historically, all three wells have shown a reduction in concentrations of iron which shows considerable variation in concentrations. The general reduction in iron concentrations may be the result of better purging of well bore volumes prior to sampling. The 2010 field parameter data for the two Twentymile Sandstone wells (No. 9 Mine Well and Well 259), do not suggest significant impact or trend. Water quality data for these Twentymile Sandstone wells are summarized in Tables 13 through 16. Plots of field conductivity over time are presented in Figure 15. Measurements during 2010 appeared consistent with historic values. In summary, elevated conductivity values were detected in the Trout Creek and Middle Sandstones. However the overall water quality of these, as well as the Twentymile Sandstone does not indicate obvious adverse impacts related to Mines 5 and 6. Note that the 7 North Angle well pump did not operate in 2010, and has not been operated for discharge since about 2003. The No. 5 Mine pump was the only active pumping performed at the mine in 2010, although as mentioned earlier, the pump failed the last quarter of 2010, so no water was pumped. A plot of the measured discharge for this point is presented in Figure 16. Figure 17 is a monthly tabulation of flow measurements for 2010. Lower pumping levels began in April 2010 due to pump operation difficulties. The No. 5 mine pump is run to maintain appropriate mine water levels. 3.1.2 Mine Water Discharge Summaries of the water quality data for mine discharge sites are presented in Tables 17 through 20. The No. 5 Mine well discharge is Colorado Department of Public Health and Environment's (CDPHE's) Colorado Discharge Permit System (CDPS, a.k.a. NPDES) discharge point 003. The 7 North Angle discharge is CDPS discharge point 024 (which did not flow in 2010). Summaries of the available water quality data for the mine discharge sites are presented in Tables 17 through 20. The No. 5 Mine discharge water quality (Figure 18) indicates dissolved solids concentrations consistent with historic values (typically under 1000 mg/L), consistent with pre-Temporary Cessation values. There was no discharge from the 7NA well in 2010. The average total dissolved solids (TDS) concentration for the No. 5 mine dewater well around 900 mg/1 in 2010. Note that there was one TDS anomaly of 1530 in December 2008. Subsequent TDS values obtained in 2010, are within the normal historical average. Historical fluctuations were historically related to the accumulation of water in the North Angle Sump location while the pump was out of order. This water was allowed to equilibrate within old workings and subsided longwall panels. The maximum concentration represents the equilibrium concentration and also provides an indication of the expected post mining TDS concentrations in rubbilized zone of underground mine workings. Likewise, this decrease illustrates the effects of flushing upon the TDS concentrations with normal periodic Page 5 G:\Environmental\EMPIRE\AHR\2010\Empire2010AHR. doc