2015-12-23_PERMIT FILE - C1982056 (2)

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overburden. Geologic structure and faulting will be essentially the same as encountered in the overlying units, and hydrologic conditions should be similar, although somewhat drier. NMD (Panels 17 -Right through 25- Right, PR03 -06 and PR06 -07) The general geology and hydrology of the remaining NMD segment has been described in the previous No. 4 and No. 5 permit revisions. Exploration drilling in 2002 was used to establish mining limits related to steep grades near the eastern flank of the Tow Creek Anticline. Combined results of the 1999 and 2002 surface 2D seismic exploration further helped to define the eastern and northern regional fault trends which control the mining boundary for the remaining NMD district longwall panels. Revised steep grade and fault limits are displayed on the Surface Geology and Wadge Seam Structure maps (Maps 5 and 6). WMD (Panels 12 -Left through 17 -Left, PR06 -07) The general geology and hydrology of the WMD is described under 2.04.5. The majority of the exploration drilling for this area was completed in the 1980's (1981 through 1989), as indicated by the drillhole locations and numbers shown on Map 6. Drilling information, along with more recent seismic work in the area, have helped to delineate structural controls and coal seam occurrence and characteristics for the WMD, as shown on Maps 5 and 6, and reflected in the geologic cross - sections (Maps 7 -9). The WMD is bounded on the north by the Twentymile Park synclinal axis and the Tow Creek anticline, on the west by a minor fault and the Fish Creek anticline, on the south by the mined -out Southwestern Mining District workings, and on the east by a major regional fault and TC's Eastern and Northern Mining Districts. Exploration drilling and seismic work do not indicate any significant additional faulting within the WMD beyond that previously identified and discussed for the general mining area. Ground water inflow conditions and water quality for the WMD are expected to be similar to the conditions encountered in the previously mined Southwestern Mining District. Inflows up to 60 gpm near fault zones, and ranging from 0 to 20 gpm over most of the WMD, are anticipated, with EC values of 3,000 -4,000 µmhos /cm. The roof and floor sample data from historic drilling and sampling in the WMD was included in the suitability evaluation, as discussed in this section. Interpretation of Overburden Geochemical Data All parameters required for analysis by the CDRMS were compared with the overburden suitability ratings developed by the Wyoming Department of Environmental Quality and the Montana Department of State Lands to determine what potential limitations might exist relative to revegetation and hydrologic considerations. Each parameter is discussed below: pH - The average pH value for the Wadge Seam and associated units was found to be 7.8 with a range from 6.2 to 8.9. For the Wolf Creek Seam and associated units, pH ranged from 7.5 to 8.8, averaging 7.9. According to the Wyoming DEQ Guideline No. 1, the reclamation suitability for both the Wadge and Wolf Creek overburden/interburden and roof and floor materials would be rated good, as shown on Tables 20B and 20C. According to the criteria published by the Montana Department of State Lands, only one of these pH values is at the suspect level of 8.8. Based on the results from a total of 20 samples for the Wadge units and 6 samples for the Wolf Creek units, TC believes that the pH of the roof and floor materials presents no problem for revegetation or water quality. Electrical Conductivity - The average electrical conductivity of the roof and floor samples was 2.1 mmhos /cm with a range of 0.6 to 3.9 mmhos /cm, and 0.31 to 1.46 mmhos /cm, averaging 0.76 mmhos /cm, for the Wadge and Wolf Creek units, respectively. The electrical conductivity values represented by these data fall within the range of normal soils and do not present potential reclamation concerns. TR13 -83 2.04 -17 11/03/14