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0 3.0 2009 HYDROLOGIC MONITORING PROGRAM <br />The BTU EC hydrologic monitoring program includes data collected specifically to meet requirements of the <br />DMG, as well as data collected to meet the requirements of the Colorado Wastewater Discharge Permit <br />System (CDPS). Note that "CDPS" parameters were formerly referred to as National Pollutant Discharge <br />Elimination System (NPDES) parameters in prior AHRs. Specific monitoring locations are illustrated on <br />Figure 2. <br />In June 2001, Technical Revision TRO1-32 was approved, allowing suspension of many DMG hydrologic <br />monitoring requirements while the mine was in temporary cessation (TC). In 2005 BTU EC began to <br />examine options for future re-activation of the mine site. In view of this considerations, BTU EC reverted <br />back to the active monitoring plan (pages 1- 14 of Exhibit 29), during the second quarter of 2006. <br />Table 1 presents a summary of hydrologic monitoring requirements. Field parameters are outlined in Table 2. <br />Water quality monitoring includes field parameters (Table 2), surface water quality parameters (Table 3), and <br />CDPS parameters (Table 4). <br />3.1 Groundwater Monitoring <br />• 3.1.1 Bedrock Wells <br />Three sandstone aquifers are found beneath the subject site. In ascending order, they are: Trout Creek <br />Sandstone, Middle Sandstone, and Twentymile Sandstone. The Eagle No. 5 and Eagle No. 6 Mines are <br />located between the Trout Creek Sandstone and the Middle Sandstone. <br />Water Levels <br />The potentiometric surface represented by water level measurements in the Trout Creek Sandstone 5 Mine <br />well (Fig. 3), has remained relatively consistent with that of 2006 through 2008, although there was a general <br />rise in water level of about 40 feet in 2009. Note that these levels are lower than levels measured prior to <br />Temporary Cessation. This drop is apparently from consistent subsurface dewatering with the No. 5 mine <br />pump. The well was historically used as a water supply, as well as for monitoring. Historical annual water <br />level fluctuations of 20 to 200 feet have been observed at this well but no seasonal pattern is evident. The <br />former Okie Plaza Trout Creek well was abandoned in June 1994 as mining advanced through its location. <br />The water levels in the Middle Sandstone formation as measured in wells TR-4, TR-7a, 81-01, 83-01, 83-02, <br />and 83-03 show fluctuations which are apparently related to dewatering and subsidence associated with <br />Mines 5 and 6. Wells TR-4, TR-7A, and 81-01 levels in 2009 are very consistent with that seen in 2006 and <br />2007. The water levels in well 83-02 (Figure 8) also show some historic fluctuations. The water level decline <br />of about 150 feet from 1987 to mid 1990 in well 83-02 was determined to be related to mine dewatering as <br />Page 3 <br />G:\Environmental\EMPIRE\AHR\2009\Empire2008AHR.doc