2011-04-29_REPORT - C1981044 (2)

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3.0 2010 HYDROLOGIC MONITORING PROGRAM The BTU EC hydrologic monitoring program includes data collected specifically to meet requirements of the DMG, as well as data collected to meet the requirements of the Colorado Wastewater Discharge Permit System (CDPS). Note that "CDPS" parameters were formerly referred to as National Pollutant Discharge Elimination System (NPDES) parameters in prior AHRs. Specific monitoring locations are illustrated on Figure 2. In June 2001, Technical Revision TRO1-32 was approved, allowing suspension of many DMG hydrologic monitoring requirements while the mine was in temporary cessation (TC). In 2005 BTU EC began to examine options for future re-activation of the mine site. In view of this considerations, BTU EC reverted back to the active monitoring plan (pages 1 - 14 of Exhibit 29), during the second quarter of 2006. Table 1 presents a summary of hydrologic monitoring requirements. Field parameters are outlined in Table 2. Water quality monitoring includes field parameters (Table 2), surface water quality parameters (Table 3), and 0 CDPS parameters (Table 4). 3.1 Groundwater Monitoring 3.1.1 Bedrock Wells Three sandstone aquifers are found beneath the subject site. In ascending order, they are: Trout Creek Sandstone, Middle Sandstone, and Twentymile Sandstone. The Eagle No. 5 and Eagle No. 6 Mines are located between the Trout Creek Sandstone and the Middle Sandstone. Water Levels The potentiometric surface represented by water level measurements in the Trout Creek Sandstone 5 Mine well (Fig. 3). Historical annual water level fluctuations of 20 to 200 feet have been observed at this well but no seasonal pattern is evident. Note that recent water levels (2006 to date) are lower than levels measured prior to Temporary Cessation. This drop is apparently from consistent subsurface dewatering with the No. 5 mine pump. Levels remained relatively consistent from 2006 through 2008. There was a general rise in water level of about 40 feet in 2009, through 2010. This is due to periodic down time from malfunctions of the No. 5 mine pump. During the last quarter of 2010, the pump failed, resulting in no discharge. The pump is anticipated to be replaced in the spring of 2011. The former Okie Plaza Trout Creek well was abandoned in June 1994 as mining advanced through its location. The water levels in the Middle Sandstone formation as measured in wells TR-4, TR-7a, 81-01, 83-01, 83-02, Page 3 G:\Environmenta1\EMPIRE\AHR\2010\EmpireN 1 OAHR.doc