2018-03-09_REPORT - C1981044 (2)

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Wells TR -4 and 83-03 are located at greater distance horizontally from the active operations for mines 5 and 6. Water levels in Well TR4 (Fig. 4) historically appear to be related to the fluctuations observed on all three of the down gradient Middle Sandstone Wells: 81-01, 83-01 and 83-02. The water level decline in TR4 prior to 1984 and the subsequent recovery up to 1988 closely parallels the trends observed in Wells 8 1 -01 and 83- 01. The decline during the first part of 1991 also parallels the trend in these two wells. However, the rapid decline during the last part of 1989 and the first part of 1990 appears to follow the trend observed in Well 83- 02 although the magnitude of decline is considerably less. Unusually large fluctuations for TR -4 for 1999 through 2000 have been attributed to a faulty pressurized line system. Well 83-03 (Fig.9) is the Middle Sandstone monitoring well located furthest (more than 1.5 miles) from active underground operations for Mines 5 and 6. The overall trend from 1984 through 2000 and again in 2006 to date suggests a similar trend to the other Middle Sandstone wells. The long term decline could be a pressure response due to the overall drop in potentiometric levels in the Middle Sandstone in the vicinity of Mines 5 and 6. The water levels in the Middle Sandstone wells had either recovered or stabilized in 1995. Note that in early 2008 and 2009 there were drops in the water level. The largest drop being approximately 25 feet in early 2009, after which water levels stabilized and started to rise again in 2012. The reason for the drops is unclear, but the level has stabilized in 2017. Historically, the groundwater gradient in the Middle Sandstone in the vicinity of the mining operation generally decreases from the southeast to the northwest. Twentymile Sandstone: Monitoring results through year 2001 and again in 2006 to date (Fig. 10) showed no apparent change in the water levels in the Twentymile Sandstone that could be attributable to mining activities. During 2017, wells 259 and 84-01 remained relatively stable as compared to 2006 through 2013, although 84-01 exhibited a slight drop in water level. 9 Mine well exhibited a rise in water elevation in 2011, and re -stabilized through 201. Note that in 2006 the first reading of the 9 mine well appeared elevated, and subsequently leveled off and has been stable through 2012. The elevated reading may be attributed to an error in monitoring equipment, as a pressurized reading was first attempted, and subsequent readings have used a water level meter. Historically, the groundwater gradient in the Middle Sandstone in the vicinity of the mining operation generally decreases from the southeast to the northwest. Water Quality Trout Creek Sandstone: The field parameter data for No. 5 Mine well does not suggest any significant mining related water quality impacts to the Trout Creek Sandstone. The water quality data for this Trout Creek Sandstone well is summarized on Table 5. A plot of field conductivity measurements is presented in Figure 11. Note that conductivity values for the No. 5 Mine well following the 2006 removal from TC appear elevated compared to earlier historical values. This may be related to consistent pumping at this site. Note that the No. 5 dewatering pump was damaged during the fourth quarter of 2010, and was removed and replaced with another pump in June 2012 when the area was dry enough to bring in a crane. In July 2013 all power was removed from the facility, and pumping ceased. Middle Sandstone: The field parameter data for the three Middle Sandstone wells (TR -4, TR -7A, 81-01) 5