PERMFILE59255 - Laserfiche WebLink

Home Browse Search

West Elk Mine . Numerous exploration boreholes have penetrated these channels and no appreciable quantities of water or unusual water pressures have been encountered. None-the-less, if the channels are fully or almost fully water saturated, and has hydraulic communication between the up-dip and down-dip reaches, appreciable groundwater could drain into the EW Seam mine workings. The volume of water that could drain into mine workings becomes progressively greater toward the northeast. Damage zones associated with the various fault zones previously described in this section have the potential to locally increase both the permeability and storage capacity of the channels, thus increased roof inflow could occur in the vicinity of the faults. Inflow estimates of as great as 500 gpm could occur if much of the fault damage zone is water saturated. Such roof inflows are not expected to persist for more than a few weeks. The Bowie Sandstone is approximately 150 to 200 feet thick and located about 10 to 15 feet below the E Seam. Because of the depositional history, mineralogical composition, geometry, and structural architecture of the Bowie Sandstone are similar to the Rollins Sandstone, there is the potential for appreciable groundwater inflows into the E Seam workings from this source particularly if the projected fault systems are saturated. However, the thickness, water level and pressure responses, and effects from B Seam mining provide insight into the potential degree of E Seam saturation. The Bowie Sandstone is less than one half the Rollins Sandstone thickness (400 feet). This difference will not affect initial inflow rates; however it will have a profound effect on the rate • of decline of inflow rates (i.e., will be considerably faster than that observed in the B Seam when saturated fault systems were encountered). No unusual water level observations and water pressures associated with the Bowie Sandstone have been reported for the more than 100 exploration boreholes that have penetrated this sandstone unit. Regional mining of the E Seam in the Oliver #2 Mine, Bowie and Oxbow mines has not resulted in significant groundwater inflows. The strongest evidence for relatively unsaturated conditions within the Bowie Sandstone is the general absence of B Seam inflows from the mine roof in the fault damage zones. The base of the Bowie Sandstone is generally 50 to 150 feet above the top of the B Seam. During the initial stags of the Rollins Sandstone inflows from the fault damage zones, some water discharged from the mine roof in a few locations within the B Seam workings. It is likely that these initial roof inflows represent the draining of Bowie Sandstone water in the fault damage zone. Fault related inflow from the underlying Bowie Sandstone has the potential to be as great as those associated with the Rollins Sandstone. However, the relationship between the responses of the Bowie and Rollins Sandstones to fault damage zones encountered during B Seam mining suffests that large and persistent inflows will not occur. Two groundwater monitoring wells (23-H-2 and 96-27-1) have been completed in the E Seam. Well 23-H-2 was completed in 1974. Water levels in 23-H-2 have been consistently neaz the bottom of the hole. There has never been enough water to obtain a sample with a bailer. Annual Hydrology Reports contain we1123-H-2 water level observations. This well is located adjacent to three other 2.05-235 Rn~isedNavemLrr 2004 PRIG