2008-03-21_PERMIT FILE - C1980007A (4)

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West Elk Mine Associates (1998). Based on observations during drilling and development of well SOM-3E the permeability of the B-Seam is estimated to be about 2.3x10-3 ft/day (1x10-6 cm/sec) (HydroGeo, 2003). The Upper Coal Member contains approximately 230 feet of interbedded shales, siltstones, lenticular sandstones, and three persistent coal seams. These seams include the D, E, and F coal seams. In portions of the Apache Rocks permit area and all of the South of Divide permit revision area, the E Seam is of significance in that it is of sufficient thickness and quality to be mused. This stratigraphic member of the Mesaverde Formation lies between the underlying marine sandstones (principally the Bowie Sandstone) and an overlying, similar but less persistent, massive, cliff-forming discontinuous channel sandstone. Groundwater inflows into the E Seam workings are expected to occur from two potential sources: 1. Sandstone channels in and near the roof of the E Seam workings. 2. Fault-related inflows from the underlying Bowie Sandstone. Extensive sandstone channels have been snapped above the E Seam in the South of Divide permit revision area. The extent of these sandstone channels are represented in Exhibit 18B on Figure 17. Because 800 or more feet of overburden generally covers the channel sandstones, it is unlikely that they have received appreciable recharge by vertical infiltration from the overlying rocks or are in active hydraulic communication with either surface water or near surface groundwater (Mayo and Associates, 1999). The most likely recharge locations are along up-dip regions in the vicinity of Minnesota Creek and possibly near the contact with the Mt. Gunnison intrusion. However no known sandstone channel outcrops have been positively identified along the Minnesota Creek drainage due to colluvial cover. While monitoring well data have documented saturation in these channels sandstones, appreciable quantities of water or unusual water pressures have not been encountered in the numerous boreholes that have penetrated these channels. This includes no water encountered in three shafts, numerous methane drainage wells, and the current development workings in the E Seam. Inflows from these sandstone channels are expected to be minor, but in association with faults such as the 14 HG could be as great as 500 gprm. Damaged zones associated with these fault zones have the potential to locally increase both the permeability and storage capacity of the sandstone channels thus potentially increasing roof inflows in the vicinity of the faults. Such roof inflows are not expected to persist for more than a few weeks (see Exhibit 18B). Mayo and Associates Exhibit 18B describes the Bowie Sandstone as having a similar depositional history and mineralogical composition to that of the Rollins Sandstone. As a result, fault-related inflows from the Bowie Sandstone beneath the E Seam have the potential to be as great as those associated with the Rollins Sandstone. However, given the lack of continued significant roof inflows into the B Seam workings, it is thought that most, if not all, of the saturation within the Bowie Sandstone near the fault zones encountered by the B Seam workings has been drained. Only a few minor seeps discharge from Bowie Sandstone outcrops between Sylvester Gulch and the Bear Mine. The absence of appreciable spring discharges further supports the idea that the Bowie Sandstone is not saturated. 2.04-66 Revised June 2005 PRIG, March 2006; Rev. April 2006 PRIO, Sep. 2007PRI2