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encountered in the Somerset Mine. The faults which have been encountered in existing mines <br /> tend to be high angle, normal faults. <br /> Hydrologic 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 <br /> groundwater monitoring stations and Map 35, which is a composite Barren Member well water <br /> level and 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 <br /> of this document and the "Cumulative Hydrologic Impact Study" document for this mine area. <br /> There are seven categories of potential aquifers that occur in the Somerset Coal Field. These <br /> are: 1) the alluvial and terrace deposits associated with the North Fork of the Gunnison River; <br /> 2) the localized, shallow alluvium along creeks tributary to the North Fork; 3) the <br /> discontinuous, lenticular and laminar sandstones of the Mesaverde Formation; 4) the Rollins <br /> Sandstone; 5) the coal seams; 6) shallow colluvial surficial deposits; and 7) fracture zones in <br /> 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 <br /> an aquitard), groundwater is generally localized and of limited areal 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 <br /> Mesaverde Formation, locally continuous permeable sands may contain groundwater which <br /> generally is recharged from the downward percolation of meteoric waters. <br /> The most continuous sandstone aquifer of any significance in the region is the Rollins <br /> Sandstone of the Mesaverde Formation. The Lower Coal Member of the Mesaverde <br /> Formation contains the Upper and Lower Marine Sandstones which may locally produce <br /> significant quantities of water. The colluvium which overlies the Barren Member of the <br /> Mesaverde Formation consists of discrete, localized units which generally follow topography. <br /> The colluvial units recharge and discharge on a seasonal basis in response to snowmelt and <br /> precipitation events. The alluvium of the North Fork consists of mixed sand, cobbles, and <br /> boulders capped by finer sands and silts. The quantity of groundwater produced from the <br /> alluvial deposits is dependent upon the thickness and extent of the deposit. <br /> Evidence shows that groundwater movement is controlled largely by fracture patterns and <br /> topography. The West Elk Mine's experience in mining the F and B Seams indicates that <br /> 13 <br />