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

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on Map 2.04.7 -1. The relative shallow strata of the affected ground water system and the relatively small area of the surface drainage system are totally dominated by the effects of seasonal irrigation. Irrigation was brought to Nucla in 1904. Map 2.04.7 -1 shows the locations of the "2 Park Lateral" the primary artery of the irrigation system in the permit area. Disturbance within the permit will primarily affect the topography, the overburden unit and the coal unit. The under- burden will be day - lighted by the pit floor but otherwise left in place. The 2nd Park irrigation water will be diverted through a HDPE pipeline during and after mining Irrigation within the permit boundary will be suspended during mining Percolation of water from the 2 Park Lateral and the flood irrigation during mining into the underlying strata will be eliminated. The effects of reducing the recharge into both the ground water and surface water systems are discussed in the appropriate places in the following. Baseline Ground Water Levels WFC and Peabody maintained and operated a ground water monitoring network in the NHN permit area consisting of 15 monitor holes (see Map 2.04.7 -1). Each monitor hole was measured for static water level on a monthly basis. While monitoring of some of these holes has been suspended, and others have been plugged and abandoned, the data from these holes provide historical reference and this information is contained in WFC's New Horizon 1 and New Horizon 2 permit documents. None of these older holes are currently being monitored. Nine new monitor holes (GW -N47 through GW -N55) were added in the NHN permit area in October 2008 (see Map 2.04.7 -1) of this application. Typical completion diagrams one each for the overburden, coal zone, and underburden well completion monitoring zones are provided in Figure 1 of Appendix 2.04.7 -1. Water level and water quality monitoring began immediately upon completion of these 9 holes on October 10, 2008. Water levels of these new wells are measured on a monthly basis and water quality samples are measured quarterly. The tabulated water level data and resulting hydrographs are contained in Appendix 2.04.7 -1. Review of the hydrographs indicates that there is separation of the three zones (underburden, coal, and overburden). Further, most of the monitoring holes show a gradual decline in water level from October '08 through March of 2009 at which point they rapidly recover again. This demonstrates the effect that the seasonal surface irrigation has on the ground water zones. The water levels decline in the Fall and Winter after the irrigation water is shut off in the " 2 nd Park Lateral" and rapidly recover in the Spring when the irrigation flow resumes. The hydrograph for GW -N9 (contained in the New Horizon 1 Permit and in the Appendix 2.04.7 -1 of this Section) demonstrates this annual cycle from September 1979 through December of 1987. An additional nest of three additional down -dip monitoring wells are to be installed before disturbance begins These wells (GW -N56, GW -N57, and GW -N58) will be constructed in the same manner as the other nine monitoring wells and will be located in the southwest area of the permit north of the Peabody Nucla Mine highwall. (See Map 2.04.7 -1). The wells will monitor overburden, coal, and underburden aquifers and will be sampled on the same schedule as the existing wells. See Appendix 2.04.7 -1 for proposed construction details of GW -N56, GW -N57, and GW -N58. Alluvial Water LeveL The drainages developed within the NHN permit area are developed on the weathered dip slope of the northeast limb of the Nucla Syncline. Map 2.04.6 -2, (the LDX Structure Contour Map) shows the structure of the NHN permit area. The primary drainage is Section 2.04.7 Page 2 November 2011