Laserfiche WebLink
With Permit Revision number 5, Oxbow Mining LLC is undertaking a new survey of surface <br />water resources in the Elk Creek Mine tract. While there aze no adjudicated water resources in <br />that tract, the USFS and USBLM requested that OMLLC inventory the resources. To date, a <br />survey was taken in the spring and a companion survey will be taken in the autumn of 2003. <br />Any resources identified will be added to Map 2.04-M5. <br />The topography of the region is characterized by steep canyons cut by the North Fork of the <br />Gunnison River and its tributaries, with several remnant alluvial terraces above the valley of the <br />North Fork. Proceeding downstream below Somerset, Colorado, the canyon widens. At Paonia, <br />Colorado, the canyon has given way to a broad alluvial plain with interspersed remnant alluvial <br />terraces. The coal to be mined is located in the Somerset Coal Field. The strata exposed in the <br />Somerset Coal Field consist of the Mancos Shale and the coal-beazing Mesaverde Formation of <br />Upper Cretaceous Age, and of the Ohio Creek Conglomerate, the Wasatch Formation and the <br />Quartz Monzonite Porphyry of Early Tertiary Age. Coal is mined from the Mesaverde <br />Formation, a 2,500 foot thick sequence of sedimentary strata overlain by the Ohio Creek <br />Conglomerate and underlain by the Mancos Shale. The strata in the Sanborn Creek and Elk <br />Creek Mines permit area dip three to five degrees north-northeast within the permit area, but <br />varies locally. <br />The Mesaverde Formation contains a number ofcoal-bearing members. The Somerset Mine <br />mined coal from the B-2 seam of the lower coal bearing (Bowie) member of the Mesaverde <br />Formation. The Sanbom Creek and Sanborn Creek East additions mined the B and C seams of <br />this member. The Elk Creek mine ramps down to the D-seam and will mine that level. The <br />Lower Coal member ranges from 260 to 350 feet thick in the Somerset Coal Field and bears three <br />minable coal seams. This member consists of interbedded and lenticular sandstones, siltstones <br />and coals, and is overlain by a massive sandstone 25 to 225 feet thick which lies directly on the C <br />seam and marks the bottom of the upper coal member. <br />Three categories of potential aquifers exist in the general area: alluvial deposits associated with <br />the North Fork of the Gunnison River and its tributaries, the Rollins Sandstone, and lenticular <br />discontinuous sandstones of the Upper Mesaverde Formation. <br />The largest alluvial aquifers are associated with the North Fork of the Gunnison River. Smaller, <br />more isolated alluvial aquifers are associated with several tributazies of the North Fork. <br />The Rollins Sandstone is the only known sandstone with sufficient porosity and lateral extent to <br />be considered a regional bedrock aquifer. The only wells in the region which are completed in <br />this aquifer are located neaz the Hawk's Nest Mine along the North Fork. <br />Localized perched bedrock aquifers exist in the discontinuous, lenticular, fine-grained sandstones <br />of the Upper Mesaverde Formation. The amount of ground water in these sandstones is <br />controlled by faulting and fracturing of the strata (secondary porosity) and the topography of the <br />recharge area. No known wells are completed in the sandstones of the Upper Mesaverde <br />Formation above the mine workings. <br />9 <br />