2003-08-26_GENERAL DOCUMENTS - C1981041

Home Browse Search

Historically, the valley has been mined for coal since the late 1800's, so the alluvial valley floor has been altered and affected by these operations. The Cameo power plant, which was a customer for coat that was mined at Roadside, lies just west of the mine site along Interstate 70. Geology Neazly the entire surface of the permit area consists of the Mesaverde Formation, a sequence of interbedded shales, siltstones and sandstones, indicative of a marine/alluvial depositional environment. Further to the south, the Wasatch and Ohio Creek Formations outcrop on the surface. The Roadside operation mines the Cameo coal seams found in the Mount Gaffield Formation of the Mesaverde Formation of sandstones, coal and shales. The Mount Garfield Formation is an example of the transitory nature of many oceanic transgressions and regressions from the Cretaceous geologic period. The Mount Garfield Formation ranges in thickness from 472 to 536 feet in the permit area and consists of three coal zones intertonguing with three prominent sandstone members. From the top to the base, the formational sequence is as follows: the Carbonera coal seam, (stratigraphic mazker of the top of the Mount Gazfield sequence), a 64-foot sandstone/shale sequence, the Cameo coal seam, 9 to 12 feet thick, Rollins sandstone member, about 114 feet thick, another shale/sandstone sequence, followed by the cliff-fomung Palisade sandstone which is 139 feet thick. Beneath the Palisade sandstone member, named for the town neazby, is the Palisade coal seam and then the Sego sandstone which forms the base of the Mount Garfield Formation. The stratigraphic column can be found in Exhibits 14, 24 and 40 of the permit application. The Cameo coal seam is the zone of interest at the Roadside Mines. Of the three coal seams in the Bookcliffs Mount Garfield Formation, only the "B" and "C" Cameo seams aze recognized as economically recoverable. The Cameo "B" seam was the primary seam extracted, although some limited mining of the "C" seam occurred through the North Portals on the west side of the Colorado River, in late 1998 and 1999. The "B" seam has also been mined via the South Portals on the east side of the river in recent yeazs, but the South Portals have been idle since January, 1997. The Cameo "B" seam in the permit azea vanes in thickness from a minimum of four feet to a maximum of eleven feet, with an average minable thickness of six feet. The coal has been classified as bituminous, with a low sulfur and high ash content. Coal extraction ceased on December 2,1999, and the operator submitted official notice of permanent cessation of operations in Mazch 2000. Further information on the geology of the permit azea can be found in Tab 6, Volume 2,of the permit application. Groundwater Hydrology The water table in the Roadside permit azea is controlled by a combination of local precipitation, topography, stratigraphy and geologic structure. The nature of the rock strata in the upper portion of the Mesaverde Formation creates a discontinuous water table. Localized perched aquifers aze found in the coal overburden which measures between 0 to 1900 feet in thickness. Groundwater moves slowly through and between these perched aquifers via the network of interconnected sandstone lenses. The strata in the Roadside Mine azea dip NE beneath the Colorado River. The Cameo Coal Seam outcrops at approximately the location and elevation of the South Portals and dips at approximately 3 degrees beneath the river to the northeast. The seam where mined at the North Portals is below the elevation of the river, but "cross dip" from the river. The entire sequence of Mesaverde that overlies the Cameo coal zone, behaves as a 11