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 Montana 



Locations of the Montana monitoring wells are shown in the Technical 

 Monitoring Schedules. 



Figure 8 depicts the water level changes since the inception of the 

 monitoring program in wells 6, 7, and 10 which are completed 

 respectively in Hart Coal, Hart Coal, and both Hart Coal and alluvium. 

 Recorded water level fluctuations in the three wells are less than 

 2 feet (0.6 m) over the period of record. The minor fluctuations 

 are mainly attributed to regional climatic conditions rather than an 

 impact resulting from the mining of coal to supply the Coronach 

 Generating Facility. Considering the variability of annual precipita- 

 tion for the period 1979 through 1986 [maximum 18.23 inches (463 mm), 

 minimum 8.89 inches (226 mm); NCAA data for Scobey, MT] the water 

 level fluctuations have been fairly minor. Although some fluctuation 

 has occurred, a trend of changing water level has not been established. 

 Instead, the monitoring results show minor changes with respect to an 

 apparently constant reference level in the coal aquifer wells. 



Water levels from wells 5, 9, and 17, which are completed to varying 

 depths in alluvium, Fort Union, and alluvium, respectively, are also 

 presented in Figure 8 for comparison. The shallow alluvial well (5) 

 and the Fort Union well (9) had water level fluctuations of less 

 than 2 feet (0.6 m) over the 6 1/2 year period of record. The 

 recently completed deep alluvial well (17) had a water level decline 

 of 2.12 feet (0.65 m) between late September and mid-December of 1986. 

 This well is located 3 miles south of the International Border in 

 a recharge area. The change is believed to represent a slightly 

 greater than average seasonal variation but further monitoring is 

 necessary to verify this Interpretaton. 



