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GROUND WATER MONITORING Bedrock Wells in the Wadge Overburden (which includes the Wadge Coal), overlying Twentymile Sandstone, and underlying Trout Creek Sandstone are monitored in the mine site area. Three Trout Creek wells are monitored for water level and water quality and one well is monitored for water level only. Four Wadge Overburden wells and two Twentymile Sandstone wells are monitored for water level and water quality. Fish Creek AVF mining area wells are reported in Appendix B. Water Levels Water levels in the Trout Creek Sandstone are plotted on Figures 3 through 6. The plot of the data for We1100~-106 (Figure 3) shows large water level fluctuations that result from frequent intermittent pumping, until 1991 when the well was pumped faiely continuously. The 1993 data for this well indicate slightly lower water levels than measured in previous years due to the more continuous pumpins. Plots of water level data from wells 001-83-107 (Figure 4) and 008-75-EFC-3-2 (Figure 5) do not indicate any long term trend in water level, alt ou hllaere appears that tLt rc e was a decline in 1993. The plot of water level data from well 006-83-48C (Figure 6), located within the mined area, indicates a declining trend since the spring of 1987, with the lowest water level recorded in the fall of 1991. Well 006-83-48C was mined through during the 1993 ~• water year, and is replaced by FCM/t2. Completion problems with FCMN2 yielded a questionable pressure reading, which appears to have resulted in an anomalously low water level value. The well is in the process of being reworked, and Halliburton will be called to complete high pressure Rrouting of the well. If this grouting techniquedoes not work a new well will have to be installed. Present mine inflow data don 'nclicate arty significant contributions from the Trout Creek Sandsto owev~ , the water level declines in some monitoring wells indicates that some~~~~rization of the aquifer to the vicinity of the mine may have occurred. of mining on the Trout Creek Sandstone Aquifer are much less than predicted in the "Probable Hydrologic Consequences" section of the mine permit application, as discussed in more detail in the "Impacts" section of this report. Plots of water levels in the Twentymile Sandstone wells are presented on Figures 7 and 8. They do not indicate any pattern that might be related to impacts from underground mining. Well 006-82-48A was also mined through during the 1993 water year, and is replaced by previously installed well 91M005. Water levels in this well declined following undermining, but this is thought to be the result of the loss of the well seal below the sandstone as mining passed, given that this well was originally drilled to the Wadge and was then converted to a monitor well. This well has subsequently been abandoned. ~ ,f _.la t /. -2- 6/10194 1:27 pm