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Mining and Water Storage Analysis <br />Raptor Pit 125 <br />Weld County, Colorado <br />Page 4 <br /> <br />Dewatering simulations were made using the estimated ultimate mine depth then raising the <br />constant head boundary seven feet above that elevation to account for the water table daylight <br />elevation that occurs during mine dewatering. These same areas were then assigned lake <br />boundaries with the lake elevations being five feet below the surface elevation as defined by <br />surveyed well elevations, topographic maps, and or, Google Earth. Figure 2 depicts the <br />extraction extents and model boundaries for all simulations. Attachments C through G present <br />model generated contours and calibration graphs for the five model runs summarized on the <br />tables below. <br />Table 1 – Cell A Dewater <br /> <br />Calibration Well Calibration Water Level Predicted Water Level Elevation Difference <br />MW-1 4779.86 <br /> <br />4778.57 -1.29 <br />MW-2 4775.47 4774.27 -1.2 <br />MW-3 4786.17 4785.88 -0.29 <br />MW-4 4777.93 4776.57 -1.36 <br /> Note: All values in feet <br /> <br /> <br />Table 2 – Dewater Cells A and B <br /> <br />Calibration Well Calibration Water Level Predicted Water Levell Elevation Difference <br />MW-1 4779.86 <br /> <br />4775.40 <br /> <br />-4.46 <br />MW-2 4775.47 4772.34 -3.13 <br />MW-3 4786.17 4785.84 -0.33 <br />MW-4 4777.93 4772.79 -5.14 <br /> Note: All values in feet <br /> <br /> <br />Table 3 – Cell A Lake Cell B 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 4774.19 -1.28 <br />MW-3 4786.17 4786.23 0.06 <br />MW-4 4777.93 4775.81 -2.12 <br /> Note: All values in feet <br />