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Only minor faulting of limited vertical displacement has been observed in the Blue Ribbon, Bear, <br />and Hawk's Nest Mines. However, in the Bowie #I Mine, a fault with a displacement of 50 feet <br />was encountered during mining. Drill hole data indicate the presence of other faults in the <br />life-of--mine azea with similar displacements. One major fault has been encountered in the Elk <br />Creek Mine. The faults which have been encountered in existing mines tend to be high angle, <br />normal faults. <br />I~droloQic Balance -Rules 2.04.5, 2.04.7, 2.05.3(4), 2.05.6(3) and 4.05 <br />Groundwater information can be found in Section 2.04.7 of the permit document. Additional <br />information can be found on Map 34 of the permit, which shows the location of the groundwater <br />monitoring stations and Map 35, which is a composite Barren Member well water level and <br />spring elevation map. <br />A description of groundwater occurrence and mining impacts on groundwater within the permit <br />and adjacent areas can be found in the "Probable Hydrologic Consequences of Mining" section of <br />this document and the "Cumulative Hydrologic Impact Study" document for this mine area. <br />There aze seven categories of potential aquifers that occur in the Somerset Coal Field. These aze: <br />1) the alluvial and terrace deposits associated with the North Fork of the Gunnison River; 2) the <br />localized, shallow alluvium along creeks tributary to the North Fork; 3) the discontinuous, <br />lenticulaz and laminar sandstones of the Mesaverde Formation; 4) the Rollins Sandstone; 5) the <br />coal seams; 6) shallow colluvial surficial deposits; and 7) fracture zones in bedrock. <br />Significant hydrogeologic units present within the West Elk Mine property include (from top to <br />bottom) the Mancos shale, the Mesaverde Formation (including the Rollins Sandstone, Lower <br />Coal Member, Upper Coal Member, and the Barren Member) and the colluvium and alluvium <br />along the drainage side slopes and valley bottoms. These hydrogeologic units are depicted on <br />Map 9 of the permit. <br />With the exception of the Mancos shale (which has an extremely low permeability and acts as an <br />aquitazd), groundwater is generally localized and of limited azeal extent within these <br />hydrogeologic units. The Mesaverde Formation is typically 2,500 feet thick at the mine and <br />consists of sandstone, shale, clay, and interbedded coal. Within the members of the Mesaverde <br />Formation, locally continuous permeable sands may contain groundwater which generally is <br />rechazged from the downward percolation of meteoric waters. <br />The most continuous sandstone of any significance in the region is the Rollins Sandstone of the <br />Mesaverde Formation. The Lower Coal Member of the Mesaverde Formation contains the <br />Upper and Lower Marine Sandstones which may locally produce significant quantities of water. <br />The colluvium which overlies the Barren Member of the Mesaverde Formation consists of <br />discrete, localized units which generally follow topography. The colluvial units rechazge and <br />discharge on a seasonal basis in response to snowmelt and precipitation events. The alluvium of <br />the North Fork consists of mixed sand, cobbles, and boulders capped by finer sands and silts. <br />The quantity of groundwater produced from the alluvial deposits is dependent upon the thickness <br />and extent of the deposit. <br />29 <br />