2018-03-09_REPORT - C1982056 (3)

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the 2017 Water Year data collected at each site. Tables 7a through 9a provide historical statistical summaries of collected data. Figures 12 through 17 provide graphical representations of water levels and selected water quality parameters recorded at each site. The potentiometric surface in the Twentymile Sandstone generally slopes from southwest to northeast. The Water levels at well 006-BRDH-7 (Figures 12), show a mild decrease over the past years, however, there was about a five foot drop in water level in mid -2007 and a three foot decrease in 2017. Water levels continued to decline through 2009, and had been stabilizing since 2012. The drops may relate to increased dewatering activities in the EMD (10 RT dewatering well) initiated around these time period. There was also drop in the conductivity in 2017 to an historic low (Figure 13). The reason for this drop is unclear at this time. TC will continue to monitor this. Water levels in well FBR-2 (Figure 14) were consistent through the late 1990s, however, in 2003 water levels dropped by approximately 56 feet, based upon a measurement in April of 2003. Through 2005, the water level 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 2017. TDS values for FBR-2 (Figure 15) went up from typical values in the upper 900's to 1170 in 2006, and were stabile through 2016 but decreased substantially back to the 900's in 2017 for unknown reasons. Well 97013TM (Figure 16) water levels appeared to be relatively stable with a downward trend since 2004 but is now trending with a mild upwards trend.. The decrease in water levels in 2001 may be related to dewatering from nearby faulting. Water levels since 2012 appear more stable. TDS values in 2011 dropped to a historic low of 540 mg/l. Since then, TDS concentrations have been rebounding (Figure 17). Trout Creek Sandstone: During 2017, 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, monitoring was conducted in the 2017 cycle year. Also per TR03-42, Trout Creek Sandstone wells 008-75-EFC and 97012TC were deactivated. 2017 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 2017 occurring at well 95M00I in lieu of FCM #2. Summaries of the Water Year data collected at each site can be found in previous AHRs. Tables 10a 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. The water pump was replaced in late 2011, at which time the electrical and support cables presented an obstruction to being able to obtain a water level reading. 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 006-8348C routinely exhibited water levels in the 6