2017-08-16_PERMIT FILE - C2010089A

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quality sampling at Well GW -N27. A K -value (hydraulic conductivity) of 40 ft/day and a transmissivity value of 261 ft2/day was determined (see Table 7-5 in Appendix 2.04.7-1) indicating that the transmissivity in the back fill at this location is 4 to 5 times higher than that of the overburden. The saturated thickness of backfill at this location is about 6.5 feet (see hydrograph for well GW -N27 in Appendix 2.04.7-1). The aquifer characteristics (production potential) of the three stratigraphic zones indicate that they are marginal at best for domestic use and totally inadequate as a source for irrigation water. Baseline Ground Water Ouality Prior to drilling the nine ground water monitoring wells (see Map 2.04.7-1 for locations of monitoring wells GW -N47 through GW -N55) the planned well locations, completion techniques, water quality sampling schedules and the water quality sample parameters were discussed with CDRMS for their input and guidance. Samples for groundwater quality analysis were collected on a quarterly basis from eight of the nine wells; however, monitoring well GW -N55 has been nearly dry to the point that collecting samples from that well is not possible. Water quality sample collections began on October 10, 2008 and will continue for the foreseeable future. The results of the groundwater quality data are reported in Appendix 2.04.7-1 of this application along with the hydrographs from the nine monitoring wells. The water quality data from the 9 new monitoring wells supplements the water quality data reported in the New Horizon 1 permit documents. Ground water monitoring wells GW -N8 and GW -N9, installed by Peabody for the old Nucla Mine, are within the NHN permit area. Several other monitoring wells, GW -N3, GW - N4 and GW-N4R are in close proximity to the NHN permit area and provide additional water quality information. NHN permit area is isolated from any potential impacts from the adjacent New Horizon Mine as a result of stream incision of the three stratigraphic zones (OB, Coal and UB) by Tuttle Draw. Additionally, the old Peabody Nucla Mine is down dip and down drainage from NHN which essentially eliminates impacts to the NHN permit area from the old mine. From the work that has been done, it appears that another nest of 3 monitoring wells is warranted. The monitoring site would be located in the southwestern portion of the permit area and would be located immediately down gradient from the limit of mining disturbance. Therefore, after permit approval and prior to new disturbance, three (3) new ground water monitoring wells were installed in the southwestern portion of the NHN permit area. The locations of these 3 new wells are shown on Map 2.04.7-1. New ground water monitor well GW -N56 will monitor the underburden (UB), well GW -N57 will monitor the coal zone (Coal) and well GW - N58 will monitor 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 the three new monitor wells are shown on Figure 3 of Appendix 2.04.7-1. These wells will be monitored and reported on the same cycle as the other ground water monitoring wells. After review of additional data and consultation with DRMS, ground water monitoring wells GW -N56, GW -N57, and GW -N58 have been designated as points of compliance. Section 2.04.7 Page 8 December 2016 (RN -01)