2017-05-08_REPORT - C1982056 (3)

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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 11995, which is down dip of 11 1 this well. Water levels in well 95M001 declined since 194, appeared to stabilize since 2002, and again declined in 2007 through 2008 (Figure 20). The declines may have been influenced by the underground mining operation Since 2009 levels appear stable with a small drop in 2016. 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 continued to decline from the early 1990s through 2012, and have appear stable since, with a small rise in 2015 and 2016. Located down dip of the TC facility water well 001-83-106 (Figure 18), had appeared stable since 2000. Declines in water level at that well in the late 1980's into the 1990s reflect effects from longwall mining that began in the western mining district in 1990, in addition to water well use. Well FBR-2-E (Figure 22), located along the eastern permit boundary exhibited consistent water levels until early 1999, then dropped about 50 feet and immediately stabilized with consistent water levels at the lower depth to date. The specific reason for this drop was not apparent, although many historical boreholes and some faulting exists in this vicinity. Water levels in 2016 were similar to the previous water years. TDS values for FBR-2-E (Figure 23) dropped in 2001, rebounded back to historical values, and began dropping again in 2003 through 2011. 2016 exhibited an historic low TDS of 95 mg/l. The exact reason for this decline is unknown, and does not appear to correspond with stable water levels. The TDS value rebounded significantly in 2013, only to drop again in 2016 (Figure 23). The reason for these jumps is unknown, but TC will continue to monitor and assess it. Well 97013TC (Figure 24) water levels remained consistent from 2004 through 2010. A drop in water level occurred in mid 2010, which is th result of being mined through. The water level continued to drop slightly during 216. TDS values for well97013TC (Figure 25) were within hi toric values from 1997 through 2012, with dr ps in 2013 and 2014. Th s also appears to be related to the wellhaving been mined thro gh. In 2015 TDS concentrations rose. Fish Creek Sandstone: Two Fish Creek Sandstone wells (91M001 and 91M004) require monitoring on a semiannual basis for water level only. An additional well (Ashley) requires semi-annual monitoring for water levels and field pari meters, and annual water quality sampling. Tables 15 through 1'7 provide summaries of the 2006 Water Year data collected at each site. Tables 15a through 17a provide historical statistical summaries of collected data at e ch site. Figure 26 provides graphical representation of the pe 'od of record water levels measured at sites 91 001 and 91 M004. 91 M004 was dry 2012 through 2015. Water levels at the Ashley well (Figure 27) dropped appreciably after subsidence in 1998, but afterward began to recover in 1999. Seasonal changes in water levels have been evident, although water levels have appeared close to the same levels from 2005 through 2016. TDS values at the Ashley well (Figure 28) have exhibited a general