2016-01-07_PERMIT FILE - C2010089A (11)

Home Browse Search

15 feet during year 4, and 30 feet during year 5. The drawdown for the coal simulation was 8 feet during year 1, 5.8 feet during year 2, 6 feet during year 3, 7.3 feet during year 4, and 8 feet during year 5. The simulations for New Horizon Mine indicated that the zero impact contour for the overburden and coal after five years of mining is approximately 4,000 feet. Further, the overburden and coal drawdown contours at New Horizon Mine did not intersect any of the model boundaries, therefore, no impact of the San Miguel River from drawdown in the deeper part of the overburden or coal were predicted. However, some of these predictions do not directly correlate with actual observations made at the old Peabody Nucla Mine (New Horizon #1 Area). For instance, draw down observed at ground water monitoring hole GW -N8 (see New horizon #1 area permit) was first detected (November 1980) when the coal face was only about 760 ft from the location of GW -N8. Suggesting that at NHN Mine the zero draw down contour is much closer to the pit face than 4000 feet and the cone of depression is much steeper. Further, during the same period another ground water monitoring hole GW -N9 located only about 854 ft north of the final highwall showed no response (and has not to date) to the drainage from the old Peabody highwall. Version v.2.8.2 of MODFIOW was used to make several simulations of the expected cone of depression. These simulations utilized the hydraulic conductivity value (2.1 ft/day) that was measured at GW -N9. The MODFOW runs (Figure 2.05.6(3)-2d and Figure 2.05.6(3)-2e) are contained in Appendix 2.05.6(3)-2 and agree well with the interpretation presented on Figure 2.05.6(3)-2c which is also contained in the Appendix 2.05.6(3)-2. Calculated average daily pit inflow for the coal and overburden zones (K value 2. 1, gradient 0.055, pit length 2217 and saturated thickness of 15 ft) is about 3840 cubic ft/day or about 20 gpm in year 1 and declining in subsequent years as the bedrock zones dry out as the result of diverting the 2nd Park Lateral water through the HDPE pipeline. As a matter of clarification, the HDPE pipeline will be moved to the approximate location of the 2nd Park Lateral after mining, backfilling and replacement of top soil has progressed far enough north. This is expected to require about 3 to 4 years after mining begins. The HDPE pipeline will be retained to prevent the irrigation water from draining into the very permeable pit backfill. This will also prevent the direct loss of irrigation water along the course of 2nd Park Lateral as occurs now. The HDPE pipeline will allow for sprinkler irrigation which is much more efficient than flood irrigation. WFC will monitor the bedrock zones and pit discharge in order to refine the extent of drawdown. The hydrological monitoring program should provide reasonably accurate measurements of the effects of mining. While there are no known uses for the bedrock zone water, WFC (as described in the water augmentation plan), has a 114 acre foot consumptive use right on the Colorado Cooperative Company ditch which could be used to mitigate any potential impact on surface water right users from pit inflow drawdown. 2) Impact on Groundwater Rights. Groundwater rights (water wells) within the immediate region (1 mile radius) around the NHN permit area are listed in Table 2.04.7-4 and shown on Map 2.04.7-8 of Section 2.04.7. In all, 29 ground water rights (wells) have been identified in the Section 2.05.6(3) Page 14 Sept. 2015 (TR -11)