2018-03-09_REPORT - C1982056 (3)

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5.0 SUMMARY AND CONCLUSIONS No significant hydrology impacts, attributable to activities at the Foidel Creek Mine, were noted during 2017. See discussion below, summarizing data assessments. Water Wells: Water levels monitored in the Twentymile Wadge Overburden wells remained stable and comparable to previously collected data, and no significant water quality influences were evident from data obtained during 2017. Twentymile Sandstone wells remained stable and comparable to previously collected data, and no significant water quality influences were evident from data obtained during 2017. Localized dewatering of the Trout Creek Sandstone appears evident in the vicinity of the TC potable water well 001-83-106 (Figure 18), although the level stabilized in 2000, and continues to be stable through 2017. The historical declining water level trend at well 001-83-107 (Figure 19), continued in 2017. This decline may be attributable to the pumping of well 001-83-106. Well monitoring at 95M001 (Figure 20) indicated a continuing decline in water levels which began in 1997, and appears to have stabilized in 2003. No significant inflows from the Trout Creek formation into the mine workings have been encountered to explain this difference in water level or to suggest that dewatering of the formation is directly attributable to mining activities. No readily apparent water quality impacts associated with mining are noted for the Trout Creek Sandstone aquifer based upon data collected during 2017. Mining related dewatering impacts were noted for the Fish Creek sandstone wells 91 M001 and 91 M004 (Figure 26), and the Ashley well (Figure 27). Wells 91M001 and 91M004 were undermined in 1995 and exhibited historic water level declines corresponding to mining activity. Water levels in these wells subsequently stabilized, exhibiting only seasonal fluctuations. Two springs (SW -1 and SW -2) are monitored in the same vicinity as 91MOO 1 and 91M004, although neither SW -1 nor SW -2 flowed in 2017. The Ashley well was undermined in 1999 and exhibited water level declines corresponding to mining activity. This well appeared to be recovering in 2000, continuing through 2017. No unusual observations are noted with respect to Foidel Creek alluvium groundwater levels. The historical increasing conductivity trend in well 001-S-5 (Figure 32) stabilized in 2004, and appears to be remaining stable through the end of 2017. No unusual observations are noted with respect to Fish Creek alluvium groundwater levels. The general water level stability noted in well 006 -AY -1 (Figure 34) since 1995, appears to continue in 2017. Overall, fluctuations at this well are insignificant. No other notable water level observations are apparent based upon review of the 2017 data. Field conductivity readings at this well appear stable over the last few years. Surface Water: 2017 was a low runoff year for Routt County. Flows on Foidel Creek, Fish Creek, and Trout Creek were lower in comparison to the normal flows. TC is still working to develop stream rating curves for the surface monitoring locations. No new flow meters were installed in 2017. TC implemented in house staff for stream gaging during 2017. 18