2013-03-14_REPORT - C1982056 (3)

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dropped an additional 84 feet. In May and June of 2003, work on the eastern end of the 16 Right panel was approaching the general vicinity of FBR -2. This anomaly may be related to work on the 16 right panel and the well's close proximity to an adjacent fault zone. In 2005 water levels began to recover, and continues through 2012. TDS values for FBR -2 (Figure 15) went up from typical values in the upper 900's to 1170 in 2006, and appears to stabile through 2012. This may be related to the increase water levels seen in 2005. Well 97013TM (Figure 16) water levels appear to be relatively stable since 2004, with a slight downward trend. The decrease in water levels in 2001 may be related to dewatering from nearby faulting. TDS values in 2011 dropped to a historic low of 540 mg /I but appear consistent with historic values in 2012 (Figure 17). Trout Creek Sandstone: During 2012, five Trout Creek Sandstone wells, 001 -83- 106, 001 -83 -107, 95M001, FBR -2 -E, and 97013TC. Note that per TR03 -42, monitoring frequency for water levels and field parameters were reduced to an annual basis, and water quality sampling to a bi- annual (every other year) basis. As such, no monitoring was conducted in the 2012 cycle year. Also per TR03 -42, Trout Creek Sandstone wells 008- 75 -EFC and 97012TC were deactivated. 2012 data is presented in Tables 10 through 14. Well FCM #2 was replaced in the fall of 1995 by monitoring well 95M001, with semi- annual monitoring during 2012 occurring at well 95M001 in lieu of FCM #2. Summaries of the Water Year data collected at each site can be found in previous AHRs. Tables l0a through 14a provide the historical statistical summaries of collected data at wells 001 -83 -106, 001 -83 -107, 95M001, FBR -2 -E, and 97013TC, respectively. Figures 18 through 25 provide graphical representations of water levels and selected water quality parameters recorded at active sites. The pumping of TC domestic water well 001 -83 -106 (Figure 18) complicates the potentiometric surface in the Trout Creek Sandstone. Water levels in well 001 -83 -106 were showing a slight increase since 1998, which appears to have stabilized back in 2003, with a slight rise from 2006 through 2012. The potentiometric surface trends prevalent in the Twentymile Sandstone and Wadge Overburden aquifers are not evident in the monitored Trout Creek wells. The previously monitored well 006- 83 -48C routinely exhibited water levels in the 7100 ft elevation range while replacement well FCM #2 exhibited levels around the 6520 ft elevation during 1995. In the fall of 1995, well 95M001 was established in part to address the apparent discrepancy in water levels between wells 006 -83 -48C and FCM #2. Water levels from well 95M001 confirm that levels recorded from well FCM #2 were accurate (Figure 20). Mining in the northern mining district began in 1995, which is down dip of this well. Water levels in well 95M001 declined since 1994, appeared to stabilize since 2002, and again declined in 2007 through 2012 (Figure 20). The declines may have been influenced by the underground mining operation. Significant inflows from the Trout Creek Sandstone into the mine workings have not been encountered to date to account for the apparent lowering of the potentiometric surface in the Trout Creek formation, as indicated by the water level data previously recorded for well 006 -83 -48C. Some dewatering of the aquifer does occur from the pumping of well 001 -83 -106 to supply the mine with domestic water. The southernmost Trout Creek well, 001 -83 -107 (Figure 19), water levels continue to decline, although subtly. Located down dip of the TC facility water well (001 -83 -106), steady declines in water level since the early 1990 may reflect effects from longwall mining that began in the western mining district in 1990, in addition to water well use (Figure 21). 6