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locations. The backfill is essentially dry with the exception of the area in the vicinity of GW -N27 <br />and GW -N10. At GW -N27 the back fill has approximately 6.4 feet of maximum saturation. At <br />GW -N10 the backfill is dry from time to time with maximum saturation of only slightly more <br />than 1 foot. GW -N27 was installed in August of 1987 and shows seasonal fluctuation of a little <br />over 3.0 feet corresponding with run off from the irrigation flow ( hydrographs for monitor wells <br />GW -10 and GW -27 are contained in the Appendix 2.04.7-1 of this section <br />Recharge and Hydrologic Boundaries The predominate source of recharge to the shallow <br />bedrock zones at the NHN permit area is direct leakage from the 2nd Park Lateral irrigation ditch <br />where it crosses the outcrop of each of the respective zones (overburden, coal and underburden), <br />and infiltration of excess flood irrigation waters into the overburden. Minor recharge also results <br />from infiltration of precipitation. Discharge is down dip to the outcrops and old Peabody high - <br />wall (see Map 2.04.5-1 of this application). Although exploration drilling has indicated the <br />presence of faults (see Map 2.04.6-2), there is no evidence that the faulting is affecting <br />groundwater flow. <br />Infiltration and Permeability of the Unsaturated Zone Using the soil hydrologic properties <br />defined by the Soil Conservation Service of the U.S. Department of Agriculture, it is possible to <br />estimate the infiltration rates of soils occurring within the vicinity of the New Horizon 1 & 2 <br />mining areas. The soils maps are included in Section 2.04.9 of this permit application. At the <br />adjacent New Horizon 2 Mine the majority of the soils have a moderate (0.6 - 2.0 in/hr) <br />permeability and infiltration rate. A minor amount of the soils have a moderately rapid (2.0 - 6.0 <br />in/hr) permeability and infiltration rate. The subsurface strata in these areas consist <br />predominately of tightly cemented sandstones and shales which act as barriers inhibiting vertical <br />percolation. However, field observation of exposed outcrops, mine high -walls, and aquifer <br />analysis data indicate that secondary porosity (weathered and fractured bedrock strata) play a <br />significant role in allowing vertically infiltrating groundwater to infiltrate through the <br />unsaturated to the saturated zone. The NHN permit area is impacted by irrigation which is a <br />primary source of infiltrating water. Infiltration as a result of precipitation is only a minor <br />component of recharge in the NHN permit area but the majority of infiltration comes from <br />irrigation. The large majority of the soils in the mining area have a slow to medium runoff <br />potential. The strata at the NHN permit area and the New Horizon Mine are the same. The <br />lithologic logs indicate that the back fill material will generally be composed of more than 50 <br />percent fragments of blasted sandstone with lesser amounts of shale and siltstone and minor <br />amounts of bentonite. The recharge capacity and permeability of the back fill material will be <br />increased due to greater porosity and hydrologic conductivities than the undisturbed strata due to <br />increased void volumes. As an example, Peabody conducted a constant discharge pumping test <br />in the backfill (spoils) of the old Peabody Nucla Mine using the formula for the well recovery at <br />GW -N27. The results of the test showed the backfill material to have a transmissivity of 261 ft2/ <br />day and a hydraulic conductivity of 40 ft/day (about 0.21 gpm/ft2) which are many times higher <br />Section 2.04.7 Page 5 March 2018 (TR -16) <br />