2022-09-29_PERMIT FILE - C1980007 (2)

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West Elk Mine fault zones that may be encountered while mining the E Seam in the SOD permit revision area (see below). However, the known or inferred fault zones aze neazly vertical in orientation and may be very difficult to identify from vertical borehole evaluation. • Water quality analyses from various surface and subsurface sources have been reviewed to assess similarities for purposes of "finger-printing" these fault inflows. Isotope analyses on samples obtained in November 1996 from the fault inflows, after a sustained period of constant 85± gpm inflow were also conducted for "finger-printing" and age-dating (residence time) purposes. These analyses indicate this water has been below the ground surface for an extended period of time. Tritium isotope analysis shows there to be no tritium within the samples for all practical purposes. This indicates that the water entered the subsurface prior to the detonation of nuclear explosives in the atmosphere (i.e., before 1943). Carbon dating suggests that the fault inflows are as much as 10,500 years old. Oxygen and hydrogen isotope ratio analyses were also conducted on fault inflows. The results show a deviation from the ratios expected for meteoric waters in the Rocky Mountain region (i.e., the Meteoric Water Line). This deviation indicates a lack of direct communication or direct recharge from a surface water source. Additional water quality analyses have been conducted and compared with known water sources in the general vicinity of the mine to assess the potential source of the fault water and the potential impacts to the water resources of the area. These data indicate that the groundwater within these two fault systems discharge from hydraulically isolated systems even though the source has been determined to be a fractured groundwater reservoir within the Rollins Sandstone beneath the B Seam coal. Distribution systems within the mine have been and will be constructed to handle these large inflows, and to separate and discharge the water to either the large capacity sumps or the surface. MCC has constructed pipelines and necessary pump stations in the entries developed north of the BEM Fault projection in the Box Canyon Mains. Water quality results indicate that the fault system water, like other inflows to the mine, is of sufficient quality to allow for direct discharge to the North Fork. Other pipelines carry sediment-laden water to the NW or NE Panels sealed sumps or to surface ponds for treatment, if necessary, and release (or use). Evaluation of downgradient migration of water stored in these sealed sumps has been considered including evaluation of the sealed workings of the Sanborn Creek Mine (a B Seam mine on the north side of the North Fork that is no longer active). The very low permeability of the coal seams and surrounding formations suggest that very limited downgradient movement of water from the sealed sump is likely. Projections of the BEM and 14HG fault systems show that, if they were to extend across the North Fork, they would not intersect any of the B Seam workings of that mine (i.e., projections are to the east of the mine workings). These fault zones do, however, project into the F Seam workings of the Hawks Nest Mine (east of the Sanborn Creek Mine) which neither encountered these faults zones nor experienced any significant groundwater inflows. MCC believes that the water-bearing BEM and 14HG . fault systems are unique to West Elk Mine and, as a result, do not extend any significant distance away from the permit area. As a result, the proposed storage of water within the Box 1.05-253 Revised June 2005 PRIO; Rev. March 1006; Rev. May 1006 PRIG