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West Elk Mine <br />• relatively large initial inflow that dimirdshed over time. Each new mining intersect generally <br />resulted in the loss of inflow from the previous mine crossing of the BEM Fault. <br />In mid-January 1997, a second SW-NE trending fault system was intersected in the 14 Southeast <br />Headgate. Inflows from this fault system (14 Southeast Headgate (14 HG) Fault) were initially <br />about 150 gpm but intersects with this fault system in adjacent entries produced an inflow of <br />approximately 8,000 gpm. <br />As a result of the BEM and 14HG Fault intersects and large respective inflows, Mayo and <br />Associates conducted an investigation to characterize these fault-related groundwater inflows <br />and the potential for encountering additional water-filled fault systems. A report was issued on <br />this subject in August 1998 (Mayo and Associates, 1998). A more thorough discussion of these <br />inflows and the results of the Mayo and Associates investigation can be found later in this <br />section. <br />Mayo and Associates also conducted a hydrogeologic characterization of the permit and adjacent <br />area in 1999. A complete copy of this report is included as Exhibit 18. That characterization was <br />based on 1) A synthesis of existing hydrogeologic information, 2) Isotopic data collected in 1998, <br />and 3) The results of Dr. Mayo's in-mine, fault-related, groundwater inflow investigation (Mayo <br />and Associates, 1998). <br />• A more recent Mayo and Associates (2004) study, considers the information obtained from <br />previous investigation both in the North Fork Valley and in eastern Utah coal mines in similar <br />geologic formations and hydrogeologic conditions as they pertain to the proposed mining of the <br />E Seam coal at West Elk Mine. A discussion of the potential effects on groundwater from E <br />Seam mining can be found later in this section and in Section 2.04.7 (Probable Hydrologic <br />Consequences). A complete version of this report is included as Appendix 18B in this permit <br />revision text. <br />As a result of these more recent investigations (Mayo and Associates, 1999, Mayo and Koontz, <br />2000 and Mayo and Associates, 2004), it has been concluded that groundwater inflows to West <br />Elk Mine issue from groundwater systems that are part of the inactive groundwater regime as it <br />relates to the genesis, composition and storage of the water. As discussed in Section 2.04.6 <br />(Other Geologic Factors That May Affect Mining Conditions), the inactive zone includes ancient <br />stored water residing in sand channel bodies, porous sections of fluvial or marine sand lenses or <br />the damaged zones of fault and fracture systems. Conversely, the active zone includes water <br />derived from rain and snowmelt stored in the near surface colluvium, alluvium or shallow <br />bedrock formations (generally less than 500 feet in depth). Demonstration of the ancient <br />characteristics of the water contained in strata surrounding West Elk Mine are indicated by the <br />10,500 year age date assigned to groundwater encountered in the BEM and 14HG Fault systems <br />based on isotopic studies (Mayo and Associates, 1998). <br /> <br />2.04-53 Revised June 2005 PRIO, Marla 2006; Rev. April 2006 PRIO, Sep. 2007PR12