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Mining and Water Storage Analysis <br />Raptor Pit 125 <br />Weld County, Colorado <br />Page 5 <br />Table 4 – Cell A Lake Cell B Lake Cell C Dewater <br />Calibration Well Calibration Water Level Predicted Water Levell Elevation Difference <br />MW-1 4779.86 <br /> <br />4777.61 <br /> <br />-2.25 <br />MW-2 4775.47 4774.30 -1.17 <br />MW-3 4786.17 4784.55 -1.62 <br />MW-4 4777.93 4775.00 -2.93 <br /> Note: All values in feet <br />Table 5 – Cell A Lake Cell B Lake Cell C Lake <br />Calibration Well Calibration Water Level Predicted Water Levell Elevation Difference <br />MW-1 4779.86 <br /> <br />4779.71 <br /> <br />-0.15 <br />MW-2 4775.47 4774.03 -1.44 <br />MW-3 4786.17 4786.22 0.05 <br />MW-4 4777.93 4777.37 -0.56 <br /> Note: All values in feet <br />Results <br />A review of Tables 1 through 5, show that the lining of mined pits at their ultimate depth will <br />have temporary effects on the local groundwater hydrology. Dewatering multiple pits at the <br />maximum predicted drawdown (Cells A&B) will likely have the greatest drawdown effects. It is <br />anticipated that cell closure of one mine cell (Cell C) will occur during the mining and dewatering of <br />the adjacent pit B, which will mitigate drawdown issues. Post lining head levels immediately up and <br />downgradient of the lined pits are within the range of normal seasonal water table elevation <br />changes. Predicted water level depressions (shadows) varied between -0.15 and -1.44 feet and <br />predicted mounding was estimated at 0.05 feet for the three lined pits. <br />Conclusions <br />The modeling results indicate that shadow-mounding effects of lining post extraction pits will <br />not adversely affect the regional groundwater hydrology. From a practical perspective it would <br />be nearly impossible to determine, with any degree of confidence, that water level changes are <br />the result of shadow or mounding verses natural (drought and precipitation) or irrigation <br />influences.