PERMFILE67351 - Laserfiche WebLink

Home Browse Search

West Elk one 18 wells permitted for monitoringpurposes (all nertnitted to MCC or its nredecessorsl Groundwater use in the general area around West Elk Mine is generally confined to shallow wells in the alluvium of the North Fork and its tributaries. There is an existing well permit for a groundwater well completed in the SW'/,NE'/a, Section 8, T145, R90W. This well was completed in a localized sandstone unit at a depth of approximately 120-140 feet and yielded approximately 2 gpm on completion. MCC owns this well, which is no longer utilized due to its limited capacity. The Rollins Sandstone was thought to be the source of water for two stock and domestic wells completed along the North Fork neaz the reclaimed Hawk's Nest East Mine, although these wells (designated 17 and 16) are probably completed above the Rollins Sandstone (Brooks and Ackerman, USGS, 1986). These "Rollins Sandstone wells" are thought to have a surface water connection with the alluvium due to the close proximity of the wells to the river and the lower salinity of the water (Prince and Arrow, 1974). Water levels for these wells indicated a gradient pazalleling the North Fork. The relative lack of groundwater within the Mesauerde Formation can be further demonstrated by reviewing information obtained during the drilling of boreholes. Figures SA through SF in Section 2.04.6, aze stratigraphic cross-sections between drill holes that indicate those intervals within each hole where groundwater was encountered. The general lack of these notations indicates the insignificance of the groundwater quantity and availability within the coal bearing strata. Mayo et al. (1997) developed a conceptual model of groundwater flow in the Book Cliffs and • Wasatch Plateau. This model was based on an analysis of physical hydrology, solute and isotopic data, and stratigraphic sequences in the coal district. The analysis included more than 300 stable and radiogenic isotopic compositions of in-mine, spring, and surface samples; hydrographs of more than 300 springs; tens of hydrographs of mine inflows; solute compositions of more than 500 in- mine, spring, and stream waters; and more than 30 monitoring well hydrographs. The data and observations from the West Elk Mine azea, which are summarized in the reports contained in Exhibits 18 and 18B (specifically for the E Seam mining in the South of Divide permit revision area), aze consistent with their observations elsewhere, and support the conceptual model of Mayo et al. (1997) when describing the hydrogeologic conditions of the West Elk Mine site. The overall pattern of groundwater flow and surface water-groundwater interactions in the study azea can be described by a conceptual model involving both active and inactive groundwater flow regimes. Active groundwater flow systems contain abundant 3H, have excellent hydraulic communication with the surface and thus are dependent on annual rechazge events and aze affected by short-term climatic variability. Groundwater in these systems circulates shallowly and has short flow paths. The active regime includes alluvial groundwater and neaz-surface exposures of all bedrock formations except, perhaps, the Mancos Shale. The "neaz surface" extends about 500 to 1,000 feet into cliff faces or exposed ridgelines where flow is controlled by fractures and channel sands. Further into the cliff faces and ridgelines the discontinuous character of channel sands prevents active groundwater flow. Monitoring well hydrographs suggest that the vertical movement of active zone groundwater is less than 100 feet below the ground surface; however, it is likely that the active zone may locally extend for 200 to 500 feet below ground surface. 1.04 -56 Revised Nwem6er 1004 PRIO