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West Elk Mine <br />to and south of the BEM and 14HG fault systems. These inferred faults, named the West Flat- <br />Iron, Deep Creek, and Gunnison Faults, aze spaced approximately equal distances apart and are <br />projected to be down-thrown to the south. Because of the small vertical displacement projected <br />on each of these faults, SRK further concluded that the faults appeaz to have developed due to a <br />very small amount of applied stress and may have developed in response to intrusion of igneous <br />rocks. <br />Each of these fault systems are thought to be the result of an igneous intrusive related to the Mt. <br />Gunnison laccolith, which intruded the Mancos Shale beneath the West Elk Mine area. <br />Intrusion-related doming of the Mancos Shale induced a low rate of stress which produced <br />extensional normal faults that propagated upwards into the Rollins Sandstone and overlying coal <br />measures of the Mesaverde Formation. As the faults propagated upward, the applied stress and <br />the strength of the strata decreased. Thus the magnitude of faulting decrease upwazd and surface <br />expressions of these faults may not be present. Fault-related fracture density is greatest in the <br />Rollins and decreases upward as the overlying sediments accommodated the strain. <br />As stated in Exhibit 18B, each of the fault-related groundwater inflows is the result of <br />pressure release from hydraulically distinct groundwater systems associated with individual <br />fault-related damage zones (Mayo and Associates, 1998; Mayo and Koontz, 2000). The <br />parallel damage zones are about 2,000 feet apart. The general absence of groundwater <br />inflows from the coal seams or mudstone overlying the B Seam indicate that the Rollins <br />Sandstone waters are not in hydraulic communication with coal seams located above the B <br />• Seam. <br />Water quality and age-dating analysis was conducted on samples obtained from the BEM and <br />14HG fault systems (Mayo and Associates, 1998). This analysis suggests that the vazious <br />groundwater samples aze: 1) Not part of a regionally continuous or azeally extensive <br />groundwater system, 2) Hydraulically connected to the surface or active groundwater regime, <br />and 3) Have a mean residence time (or age) of approximately 10,500 yeazs. Details of this <br />analysis can be found in Appendix 18 and its relevance to E Seam mining in the South of Divide <br />permit revision area can be found in Appendix 18B. <br />E Seam mining is expected to encounter many of the same fault systems and possibly two <br />inferred zones not intercepted in the B Seam workings. Mayo and Associated (2004) projects <br />that the previously intercepted fault zones may have insignificant nuisance waters associated <br />with the fault zones and inflows from the Bowie Sandstone beneath the E Seam will be small or <br />non-existent. The exception may be where tectonic faults have crossed sandstone roof channels <br />allowing the channel sandstones and fractured damage zones to store water. Inflows from these <br />sandstone channels may reach as much as 500 gpm in that instance. <br />In summary, the West Elk Mine site can be chazacterized as having decreasing permeability with <br />depth as a result of lithologic changes and smaller fracture aperture, limiting downward percolation <br />of groundwater through the bedrock units, and resulting in localized dischazge via springs generally <br />above the F Seam. The exceptions are the damaged zones associated with fault systems <br />encountered in the eastern portion of the mine as described above. Additional discussion of these <br />• fault-related inflows can be found in Section 2.05.6. <br />1.04 -73 Revised Nwem6er 1004 PRt 0 <br />