2018-07-02_PERMIT FILE - C2010089A (19)

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HYDROLOGY DESCRIPTION The NHN permit area is adjacent to Elk Ridge Mining and Reclamation's active New Horizon 2 Mine and incorporates part of the old Peabody Nucla Mine. Peabody performed detailed hydrologic studies at the New Horizon 1 & 2 Mine areas (formerly called the Nucla and Nucla East mine areas, respectively). Please refer to the original Peabody permit application: Volumes B, C, D, E, F, and G for hydrology data related to old Nucla Mine (New Horizon 1 Mine area). In the spring of 2008, Elk Ridge Mining personnel met with DRMS to discuss and agreed upon a hydrologic monitoring program for the NHN permit area. The plan resulted in the drilling of 9 hydrologic monitoring wells (GW -N47 through GW -N55) during the fall of 2008 and the establishment of 19 surface water monitoring stations (SW -N200 through SW -N218) and inclusion of two current New Horizon 2 Mine stations (SW -N1 and SW -N3) to supplement the existing data that had been collected in the New Horizon 1 & 2 Mine areas. Of the nine groundwater monitoring wells, three (GW -N49, GW -N52, and GW -N55) were drilled and completed as overburden monitoring wells, three were completed as coal zone monitoring wells (GW -N48, GW -N51, and GW -N54) and three were completed as underburden monitoring wells (GW -N47, GW -N50, and GW -N53). Map 2.04.7-1 shows the locations of the nine groundwater monitoring wells, and also shows the location of six groundwater monitoring wells that were completed by Peabody in and adjacent to the incorporated New Horizon 1 Mine area. Map 2.04.7-1 also shows the locations of the 21 surface water monitoring sites (SW -N1, SW -N3 and SW200-SW218), as well as monitoring sites established by Peabody for New Horizon 1 Mine. After permit approval and prior to disturbance, three (3) groundwater monitoring wells were installed in the southwestern portion of the NHN permit area. The locations of these 3 wells are shown on Map 2.04.7-1. The three wells and the nine listed above make up NHN's groundwater monitoring program. Groundwater monitor well GW -N56 monitors the underburden (UB), well GW -N57 monitors the coal zone and well GW -N58 monitors the overburden. GW -N56 was completed on August 8, 2012 while GW's N57 and N58 were completed on August 9, 2012. The completion diagrams for these three monitoring wells are shown on Figure 3 of Appendix 2.04.7- 1. All active wells will be monitored and reported in the Annual Hydrology Report. After review of additional data and consultation with DRMS, groundwater monitoring wells GW -N56, GW - N57, and GW -N58 have been designated as points of compliance. Three (3) wells (GW -N47, -N48, -N49) located in northwestern portion of the NHN permit have been removed from the monitoring plan and will be reclaimed upon approval by DRMS. Since the wells are located outside the NHN mining area (%2 mile north) and are neither up nor down gradient from the NHN disturbance area, they will likely not be beneficial in monitoring the extent and magnitude of mining related impacts. The remaining wells provide monitoring both up gradient (GW -N50, -N51, -N52) and down gradient (GW -N53, -N54, -N55) of the NHN disturbance area, including three down gradient points of compliance (GW -N56, -N57, -N58). Section 2.04.7 Page 1 March 2018 (TR -16)