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in 2007 through 2008 (Figure 20). The declines may have been influenced by the underground mining operation <br />Since 2009 levels appear stable. <br />Significant inflows from the Trout Creek Sandstone into the mine workings have not been encountered to date to <br />account for the apparent lowering of the potentiometric surface in the Trout Creek formation, as indicated by the <br />water level data previously recorded for well 006-83-48C. Some dewatering of the aquifer does occur from the <br />pumping of well 001-83-106 to supply the mine with domestic water. <br />The southernmost Trout Creek well, 001-83-107 (Figure 19), water levels continued to decline from the early <br />1990s through 2012, and have appear stable since, with a small rise in 2015. Located down dip of the TC facility <br />water well 001-83-106 (Figure 18), had appeared stable since 2000. Declines in water level at that well in the late <br />1980's into the 1990s reflect effects from longwall mining that began in the western mining district in 1990, in <br />addition to water well use. <br />Well FBR-2-E (Figure 22), located along the eastern permit boundary exhibited consistent water levels until early <br />1999, then dropped about 50 feet and immediately stabilized with consistent water levels at the lower depth to <br />date. The specific reason for this drop was not apparent, although many historical boreholes and some faulting <br />exists in this general vicinity. Water levels in 2015 were similar to the previous water years. TDS values for <br />FBR-2-E (Figure 23) dropped in 2001, rebounded back to historical values, and began dropping again in 2003 <br />through 2015. 2011 exhibited an historic low TDS of 380 mg/l. The exact reason for this decline is unknown, <br />and does not appear to correspond with stable water levels. The TDS value rebounded significantly in 2014, only <br />to drop again in 2015 (Figure 23). The reason for these jumps is unknown, but TC will continue to monitor and <br />assess it. <br />Well 97013TC (Figure 24) water levels remained consistent from 2004 through 2010. A drop in water level <br />occurred in mid 2010, which is the result of being mined through. The water level continued to drop during <br />2015. TDS values for well 97013TC (Figure 25) were within historic values from 1997 through 2012, with <br />drops in 2013 and 2014. This also appears to be related to the well having been mined through. In 2015 TDS <br />concentrations rose. <br />Fish Creek Sandstone: Two Fish Creek Sandstone wells (91M001 and 91M004) require monitoring on a <br />semiannual basis for water level only. An additional well (Ashley) requires semi-annual monitoring for water <br />levels and field parameters, and annual water quality sampling. Tables 15 through 17 provide summaries of the <br />2006 Water Year data collected at each site. Tables 15a through 17a provide historical statistical summaries of <br />collected data at each site. Figure 26 provides graphical representation of the period of record water levels <br />measured at sites 91MOO 1 and 91M004. 91M004 has been dry the last two years. <br />Water levels at the Ashley well (Figure 27) dropped appreciably after subsidence in 1998, but afterward began to <br />recover in 1999. Seasonal changes in water levels have been evident, although water levels have appeared close <br />to the same levels from 2005 through 2015. TDS values at the Ashley well (Figure 28) have exhibited a general <br />decline since 1996, rose somewhat in 2005, and generally exhibited a dropped again in 2011 through 2013. <br />Levels appeared stable the last two years. Field measurements and water quality parameters for the Ashley well <br />7 <br />