2012-06-20_PERMIT FILE - C2010089A (10)

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Meehan Draw which is developed on bedrock. No alluvial wells were installed due to the lack of alluvium. Overburden Water Levels. Water levels at the three new overburden monitoring holes, GW- N49, GW -N52, and GW -N55, (see completion diagrams, tabulated data and hydrographs in Appendix 2.04.7 -1) have been monitored monthly since October 10, 2008. Two of these holes (GW -N49 and GW -N52) show the seasonal fluctuation resulting from the seasonal irrigation. Water monitoring hole GW -N55 is essentially dry showing a slight increase in water level since completion but without even enough water to collect samples. This suggests that two conditions exist in the overburden zone: (1) vertical permeability of the unweathered overburden below the zone of weathering is low, and (2) the lateral permeability is also low as the unweathered overburden is not reflecting up dip recharge from the 2 Park Lateral. The amplitude of the seasonal fluctuation at GW -N49 is about 12 ft. whereas the annual fluctuation at GW -N52 is over 19 ft. Map 2.04.7 -2 and Map 2.04.7 -3, respectively show the potentiometric surfaces and direction of flow of the overburden zone at both the lowest level (winter conditions, no irrigation flow) and highest level (summer conditions with full irrigation). The gradient of the potentiometric surface varies from about 0.023 ft/ft to about 0.044 ft/ft during the seasonal low levels and 0.033 ft/ft and 0.05 ft/ft during seasonal high levels. The area directly north of the old Peabody highwall has a low seasonal gradient of 0.022 ft/ft and a gradient during the irrigation season of 0.082. The difference in gradients from summer to winter further demonstrates the ground water mounding effects of the recharge from irrigation. The hydrograph from monitoring hole GW -N8 (monitoring suspended) shows the response in 1983 to mining at Peabody's Nucla Mine, (see GW -N8 hydrograph in the Appendix 2.04.7 -1 of this section.). Dakota Coal Water Levels All three of the new coal zone monitoring holes, (GW -N48, GW- N51, and GW -N54), demonstrate the seasonal fluctuations in water levels resulting from irrigation (see Appendix 2.04.7 -1 of this application). Comparing the coal zone hydrographs with the overburden zone hydrographs indicates that the lateral permeability of the coal zone is higher than that of the unweathered overburden. The response to the start of Spring irrigation at hole GW -N54 is about a month later than at holes GW -N48 and GW -N51 suggesting that rise in water level at that hole is due to up dip recharge. This further suggests that the coal zone at this monitoring hole is relatively well confined and isolated from the overburden zone and the underburden zone. Hole GW -N54 has about 10 ft. of artesian head during the summer months. The amplitude of the seasonal fluctuation due to irrigation is about 12 ft., 19 ft., and 9 ft for holes GW -N48, GW -N51, and GW -N54, respectively. Map 2.04.7 -4 and Map 2.04.7 -5, respectively shows the potentiometric surfaces and direction of flow of the coal zone at both the lowest level (winter conditions, no irrigation flow) and highest level (summer conditions with full irrigation). The gradient of the potentiometric surface varies from about 0.029 ft/ft to about 0.047 ft/ft during the seasonal low levels and 0.033 ft/ft and 0.051 ft/ft during seasonal high levels. The area directly north of the old Peabody highwall has a low seasonal gradient of 0.028 ft/ft and a gradient during the irrigation season of 0.079. Underburden Water Levels Two (GW -N47 and GW -N50) of the three new under burden zone monitoring holes that have been monitored since October 10, 2008 clearly show the seasonal effects of surface irrigation (see Appendix 2.04.7 -1 for hydrographs). Similar to the Section 2.04.7 Page 3 November 2011