Laserfiche WebLink
West Elk Mine(C-1980-007) MT-9 <br /> prominent and consistent throughout the existing F and B Seam workings. Fracture sets and cleat <br /> orientations of the E Seam are also the same. The major cleat direction in the nearby Bear and Elk <br /> Creek mines is from North 70 to 75 degrees east and is probably representative of the face cleat <br /> direction in the Jumbo Mountain area. <br /> There are seven categories of potential aquifers that occur in the Somerset Coal Field. These are: 1) <br /> 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, lenticular <br /> and laminar sandstones of the Mesaverde Formation; 4) the Rollins Sandstone; 5) the coal seams; 6) <br /> shallow colluvial surficial deposits; and 7) fracture zones in the bedrock. <br /> Significant hydrogeologic units present within the West Elk Mine permit boundary include (in <br /> ascending order) the Mancos shale, the Mesaverde Formation (including the Rollins Sandstone, <br /> Lower Coal Member, Upper Coal Member, and the Barren Member) and the colluvium and alluvium <br /> along the drainage side slopes and valley bottoms. With the exception of the Mancos shale (which <br /> has an extremely low permeability and acts as an aquitard), groundwater is generally localized and of <br /> limited areal extent within these hydrogeologic units. The Mesaverde Formation is typically 2,500 <br /> feet thick at the mine and consists of sandstone, shale, clay, and interbedded coal. Within the <br /> members of the Mesaverde Formation, locally continuous permeable sands may contain <br /> groundwater which generally is 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 Upper and <br /> Lower Marine Sandstones which may locally produce significant quantities of water. The colluvium <br /> which overlies the Barren Member of the Mesaverde Formation consists of discrete, localized units <br /> which generally follow topography. The colluvial units recharge and discharge on a seasonal basis in <br /> response to snowmelt and precipitation events. The alluvium of the North Fork consists of mixed <br /> sand, cobbles, and boulders capped by finer sands and silts. The quantity of groundwater produced <br /> from the alluvial deposits is dependent upon the thickness and extent of the deposit. Evidence shows <br /> that groundwater movement is controlled largely by fractures and topography. The West Elk Mine's <br /> experience in mining the F and B Seams indicates that groundwater inflows are associated with <br /> fractures and are seasonal. <br /> Groundwater use in the general area around the West Elk Mine is confined to shallow wells in the <br /> alluvium of the North Fork of the Gunnison River and its tributaries. No private, commercial, or <br /> industrial wells are presently located within or immediately down-gradient of the permit area, other <br /> than the infiltration gallery which supplies domestic water for the town of Somerset and the Elk <br /> Creek Mine. <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 northern <br /> portion of the permit area. Sylvester Gulch has perennial flows in its lower reaches through the mine <br /> area. Minnesota Creek and its tributaries, Horse Creek, South Prong, Lick Creek, Dry Fork, and East <br /> Page 7 of 14 <br />