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West Elk Mine <br />• In mid-January 1997, a second SW-NE trending fault system was intersected in the 14 <br />Southeast Headgate. Inflows from this fault system (14 Southeast Headgate (14 HG) Fault) <br />were initially about 150 gpm but intersects with this fault system in adjacent entries <br />produced an inflow of 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 <br />inflows and the potential for encountering additional water-filled fault systems. A report <br />was issued on this subject in August 1998 (Mayo and Associates, 1998). Amore thorough <br />discussion of these inflows and the results of the Mayo and Associates investigation can be <br />found later in this section. <br />Mayo and Associates also conducted a hydrogeologic chazacterization of the permit and adjacent <br />azea 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 <br />similar geologic formations and hydrogeologic conditions as they pertain to the proposed <br />• mining of the E Seam coal at West Elk Mine. A discussion of the potential effects on <br />groundwater from E Seam mining can be found later in this section and in Section 2.04.7 <br />(Probable Hydrologic Consequences). A complete version of this report is included as <br />Appendix 18B in this permit revision text. <br />As a result of these more recent investigations (Mayo and Associates, 1999, Mayo and <br />Koontz, 2000 and Mayo and Associates, 2004), it has been concluded that groundwater <br />inflows to West Elk Mine issue from groundwater systems that are part of the inactive <br />groundwater regime as it relates to the genesis, composition and storage of the water. As <br />discussed in Section 2.04.6 (Other Geologic Factors That May Affect Mining Conditions), <br />the inactive zone includes ancient stored water residing in sand channel bodies, porous <br />sections of fluvial or marine sand lenses or the damaged zones of fault and fracture <br />systems. Conversely, the active zone includes water derived from rain and snowmelt stored <br />in the near surface colluvium, alluvium or shallow bedrock formations (generally less than <br />500 feet in depth). Demonstration of the ancient characteristics of the water contained in <br />strata surrounding West Elk Mine are indicated by the 10,500 year age date assigned to <br />groundwater encountered in the BEM and 14HG Fault systems based on isotopic studies <br />(Mayo and Associates, 1998). <br />Regional Groundwater Conditions <br />For the most part, the Mesaverde Formation is dry or the rock units are of such low permeability <br />that they yield insufficient water for sustained use. Even the extensive Rollins Sandstone, a thick <br />• basal sandstone immediately above the Mancos Shale, has been found to be highly cemented and a <br />2.04 -53 Revised Nwem6er 1004 PR70 <br />