2015-08-18_PERMIT FILE - C1982056A (4)

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inflow rates quickly declined to 65 gallons per minute (2001 & 2002 monitoring). The source of the water was from the roof (ie: Wadge overburden). No vertical or horizontal offsets were observed; therefore the inflow was not from fault. TCC enlisted the assistance of a consultant (James G. Nalven Consulting) to obtain a better understanding of the reason for the elevated inflows in this area, since this was the most water TCC had encountered since mining was initiated in the early 1980's. Mr. Nalven visited the mine site on December 2 °a and P, 1997, to investigate the source of the inflows. Preliminary evaluation indicated that the flow was coming from an area that is coincident with the Foidel Creek lineament or valley. This portion of the 6 -Right gate -road also has the lowest overburden (350 to 450 feet) in the EMD. The area is also located were the dip is increasing significantly along the steep (8 to 25 percent grade) western flank of the Twentymile Park Syncline. This unique combination of topographic and geologic features appears to have resulted in increased fracturing of the rock, open joints, and movement along bedding planes that have combined to increase permeability in the immediate area. In addition to the flow measurements, field EC readings were obtained to provide insight into the source of the water. The EC readings were recorded at 4,000 mmhos /cm. This reading corresponds with the EC values obtained from the adjacent and up -dip surface mine spoil water. Previously, TCC had experienced spoil water migrating into the underground workings and elevating the EC levels in the Wadge Overburden. This phenomenon has been recorded in the Annual Mine Inflow studies. During active operations in this area, the mine inflows were captured at the face, pumped to a "Shark Tank ", and then pumped from the section into an underground sump. During 1997, roof and floor samples were obtained from Drillholes 97 -006 and 97 -007. The data for these drillholes is presented in Tables 20D and 20E. A review of the data indicates that all parameters, except for boron, are within or below the values previously reported by TCC. The boron concentration is relatively low, at 1.57 mg/kg, and does not represent any environmental concern. It is important to note that the geochemical data is relatively consistent over the entire mine property, indicating that the roof and floor sampling and analysis that has been conducted is both adequate and representative. Previous studies (Robson and Stewart, 1990) indicate that the lower members of the Williams Fork Formation (including the Wadge Seam, Wolf Creek Coal Seam, and Wadge /Wolf Creek Interburden) function as a single hydrologic unit in this area. This conclusion is reinforced by more recent radio - isotope analysis of groundwater in the area, indicating that the groundwater is over one - million years old, and that there is little or no groundwater movement or mixing in the lower portion of the formation. Based on this information and limited historic and more recent drilling, the geologic and hydrologic conditions for the Wolf Creek Coal Seam and Wadge /Wolf Creek interburden are expected to be similar to those characterized through previous baseline work and actually encountered for the Wadge Coal Seam and overburden. Geologic structure and faulting will be essentially the same as encountered in the overlying units. Based on previous drillholes in this area that extended down to the underlying Trout Creek Sandstone, more recent underground drilling extending into the units immediately below the Wolf Creek Seam, and monitoring wells screened in the Wadge/Wolf Creek Interburden and the Wolf Creek Seam, the Wadge /Wolf Creek interburden and the Wolf Creek Seam are expected to function as a single hydrologic unit and to be somewhat drier than the Wadge Seam and associated overburden, but with similar water -table ground water characteristics. Additional drilling and geochemical analyses were conducted (MR's 13 -272, 13 -275, and 14 -276) in order to better define the conditions and characteristics of the Wadge /Wolf Creek Interburden and the Wolf Creek Coal Seam and partings to support review and permitting for full -scale mining of the WCR. This supplemental information has been included in Exhibit 53, Wolf Creek Reserve Geologic and Mine Plan Information,. NMD and Northern Portion of WCR (NMD Panels 12 -Right through 16- Right, PR99 -05, TR13 -83) The general geology and hydrology of the NMD has previously been described in the original Foidel Creek Mine application, and subsequently updated through Permit Revisions 3 and 4. The 1998 drilling program was used to validate the prior description. TC did not find any unsuspected geologic conditions that would modify the original descriptions. TR13 -83 2.04 -16.2 11/03/14