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determine the reason for this effect. <br />Wells TR-7A and TR-4 have historically indicated a slight reduction in concentrations of major ions over <br />time. Historically, all three wells have shown a reduction in concentrations of iron which shows considerable <br />variation in concentrations. The general reduction in iron concentrations may be the result of better purging <br />of well bore volumes prior to sampling. <br />The 2006 field parameter data for the two Twentymile Sandstone wells (No. 9 Mine Well and Well 259), do <br />not suggest significant impact or trend. Water quality data for these Twentymile Sandstone wells are <br />summarized in Tables 13 through 16. Plots of field conductivity over time are presented in Figure 15. <br />Measurements during 2006 appeared consistent with historic values. <br />In summary, elevated conductivity values were detected in the Trout Creek and Middle Sandstones. However <br />the overall water quality of these, as well as the Twentymile Sandstone does not indicate adverse impacts <br />related to Mines 5 and 6. <br />Note that the 7 North Angle well pump did not operate in 2006. The No. 5 Mine pump was the only active <br />pumping perfomed at the mine in 2006. A plot of the measured discharge for this point is presented in Figure <br />16. Figure 17 is a monthly tabulation of flow measurements for 2006. The No. 5 mine pump is run to <br />maintain appropriate mine water levels. <br />3.1.2 Mine Water Discharge <br />. Summaries of the water quality data for the mine discharge are presented in Tables 17 through 20. The No. 5 <br />Mine well discharge is Colorado Department of Public Health and Environment's (CDPHE's) Colorado <br />Discharge Permit System (CDPS, a.k.a. NPDES) discharge point 003. The 7 North Angle discharge is CDPS <br />discharge point 024. Summaries of the available water quality data for the mine discharge sites are presented <br />in Tables 17 through 20. <br />The No. 5 Mine discharge water quality (Figure 18) indicates dissolved solids concentrations consistent with <br />historic values (typically under 1000 mg/L). The average dissolved solids concentration for the 7 North Angle <br />were around 1150 mg/1 in 2000 which was a return to values common in 1994 and 1995. Historically, this <br />trend was related to the accumulafion of water in the North Angle Sump location while [he pump was out of <br />order. This water was allowed to equilibrate within old workings and subsided longwall panels. The <br />maximum concentration represents the equilibrium concentration and also provides an indication of the <br />expected post mining TDS concentrations in rubbleized zone of underground mine workings. Likewise, this <br />decrease illustrates the effects of flushing upon the TDS concentrations with normal periodic discharge. <br />3.1.3 ALLUVIAL WELLS <br />Water Sediments in the Williams Fork River Alluvium are monitored via three alluvial wells in the general <br />area of the loadout facilities and underground discharge sediment ponds. These include wells AVF-3, AVF-5, <br />and AVF-6. Water quality data for these three wells is provided in Tables 21 through 26. Conductivity data is <br />Page 5 <br />• 1:\Env\Empire\AHR\2006\Test\Empire2006AHR.doc <br />