2008-04-01_REPORT - C1981044 (5)

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• 2006, following post Temporary Cessation reactivation of monitoring. The consultant that monitors these wells has been Linavailable for the last two weeks. We will discuss the possibility of their monitoring the wrong well(s), when they return. BTU-EC will continue to monitor these sites in order to determine the reason for this effect, and will submit a separate letter discussing this anomaly in the near future, and in the 2008 AHR. 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 2007 field parameter data for the two Twentymile Sandstone wells (No. 9 Mine Well and We11259), do not suggest significant impact or trend. Water quality data for these Twentymile Sandstone wells are summarized in 'Cables 13 through 16. Plots of field conductivity over time are presented in Figure 15. Measurements during 2007 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 adverse impacts related to Mines 5 and 6. Note that the 7 rTorth Angle well pump did not operate in 2006 or in 2007. The No. 5 Mine pump was the only active pumping performed at the mine in 2007. A plot of the measured discharge for this point is presented in Figure 16. Figure 17 is a monthly tabulation of flow measurements for 2007. The No. 5 mine pump is run to maintain appropriate mine water levels. • 3.1.2 Mine Waiter Discharge Summaries of the; water quality data for the mine discharge 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. Summaries of the available water quality data for the mine discharge sites are presented in Tables 17 throi.~gh 20. The No. 5 Mine discharge water quality (Figure 18) indicates dissolved solids concentrations consistent with historic values (t:ypically under 1000 mg/L), consistent with pre-Temporary Cessation values. There was no discharge from the 7NA well in 2006 or 2007. The average dissolved solids concentration for the 7 North Angle averaged around 1100 mg/1 in 2000. 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 concc;ntration and also provides an indication of the expected post mining TDS concentrations in rubblized zone of• underground mine workings. Likewise, this decrease illustrates the effects of flushing upon the TDS concentrations with normal periodic discharge. 3.1.3 ALLUVIAL WELLS Water Sediments in the Williams Fork River Alluvium are monitored via three alluvial wells in the general area of the loadout facilities and underground discharge sediment ponds. These include wells AVF-3, AVF-5, • Page 5 G:~Environmental~EM PIREWHR~2007~Empire2007AHR.doc