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Lower Coal Member, Upper Coal Member, and the Barren Member) and the colluvium and <br /> alluvium along the drainage side slopes and valley bottoms. These hydrogeologic units are <br /> depicted on Map 9 of the PAP. <br /> With the exception of the Mancos shale (which has an extremely low permeability and acts as an <br /> 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 Mesaverde <br /> Formation, locally continuous permeable sands may contain groundwater which generally is <br /> recharged 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 recharge 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 /> Evidence shows that groundwater movement is controlled largely by fractures and topography. <br /> The West Elk Mine's experience in mining the F and B Seams indicates that groundwater inflows <br /> are associated with fractures and are seasonal. As discussed in the previous section of this <br /> document, a fault system was encountered while development mining in the B Seam, which <br /> produced as much as 8,000 gpm of groundwater inflow to the mine. <br /> Groundwater use in the general area around the West Elk Mine is confined to shallow wells in <br /> the alluvium of the North Fork of the Gunnison River and its tributaries. No private, <br /> commercial, or industrial wells are presently located within or down-gradient adjacent the permit <br /> area, other than the infiltration gallery which supplies domestic water for the town of Somerset <br /> and the Elk Creek Mine. <br /> A description of the surface water system can be found in Section 2.04.7 of the PAP. Supporting <br /> information is contained in Map 34, which illustrates the drainages associated with the West Elk <br /> Mine coal lease area; Map 37, which delineates the location of all known springs on the coal <br /> lease area, and Map 36, which shows the reservoirs and irrigation ditches associated with the <br /> Minnesota Creek Basin. <br /> A description of the surface water occurrence and mining impacts on adjacent areas can be found <br /> in the "Probable Hydrologic Consequences of Mining" section of this document, and the <br /> "Cumulative Hydrologic Impact Study" document for this mine area. <br /> All of the streams draining the West Elk Mine permit area are tributaries to the North Fork of the <br /> Gunnison River. Lone Pine Gulch and Gribble Gulch are ephemeral streams draining the <br /> northern portion of the permit area. Sylvester Gulch has perennial flows in its lower reaches <br /> through the mine area. Minnesota Creek and its tributaries, Horse Creek, South Prong, Lick <br /> Creek, Dry Fork, and East Fork, drain the southern portion of the permit area. Deep Creek <br /> 19 <br />