2022-02-22_PERMIT FILE - C1980007 (5)

Home Browse Search

West Elk Mine 2.04-45 Rev. 11/04- PR10, 04/06- PR10, 09/07- PR12, 10/08- PR14; 01/22- MR459 Seam mining was under the least amount of cover, chances of surface water, combined with shallow overburden and/or major fractures, impacting mining operations would have been highest in the F Seam. Underground mapping of miles of F Seam workings has shown a relationship between shallow cover under drainages and poor roof conditions caused by water, but has not shown a clear-cut relationship between fracture zones and wet roof conditions, with the exception of the Sylvester Gulch entries. Since the E Seam is deeper than the F Seam, it can be assumed that the effects of shallow overburden and fracture related water on underground mining operations in the E Seam would be less than in the F Seam, even though immediate roof rock sequences and types a re similar. The B Seam is deeper still, and seems to have more competent roof rocks than the E and F Seam, so it can be assumed that near surface and fracture related water would have little impact on a mining operation in the B Seam. Where depths of cover are less, water may be encountered beneath the more prominent drainages. Groundwater in the inactive zone is ancient stored water residing in sand channel bodies, within the porous sections of fluvial or marine sand lenses, or within the damaged zones or fault and fracture systems. The strata containing water surrounding the West Elk Mine region has ancient water in the inactive zone that has been age dated to approximately 10,500 years (A. Mayo, 1998). The residence time is consistent with similar non-tributary water found in coal mines of the Wasatch Plateau and Book Cliffs of Utah. Melt-off of Pleistocene glaciers from the West Elk Mountains south and east of MCC’s coal lease holdings provided an ample source of water of the appropriate age as the source for the inactive zone water. In coal mines inactive zone inflows typically occur as: 1. Roof inflows from sandstone channels located in the lower portion of the Mesaverde Group. Inflows from overlying sandstone channels issue from roof bolt holes, vertical borings, or the bottoms of channels exposed during mining. 2. Floor inflows occurring as springs from shoreface and foreshore marine sandstones. 3. Roof and or floor inflows issuing from damage zones associated with faulting. These damage zone inflows can significantly increase the inflow rates and total volumes of flows associated with marine sandstone springs. In unusual circumstances minor amounts of near surface (active zone) groundwater can enter the mine environment along fault damage zone. The A through C Seam coal sequence is sandwiched between two large marine sandstone bodies, the Rollins and Bowie Sandstones. These sands have moderate to good porosity at 5 to 16 percent, but with a permeability of .001 Darcy or less. These marine sandstones could store water but don’t. Inflows from roof channels or springs not associated with faulting are rare or nonexistent. Indeed, exploration drilling on or near MCC’s coal leases during the past 40 years has not encountered significant water in the coals or sandstones. Perched aquifers are rarely encountered and have restricted lateral extents. The low transmissivity and poor aquifer characteristics of the coals have also been evidenced by interception of water bearing fault systems in the B Seam development. On four separate