GENERAL44107 - Laserfiche WebLink

Home Browse Search

IX. Cumulative H drolo is Im act Stud and Probable H drolo is onsequences - u es an c This Cumulative Hydrologic Impact Study (CHIS) for a portion of the Yampa River basin has been prepared by the Colorado Mined Land Reclamation Division (CMLRD) pursuant to Rule 2.07.6(2)(c). This CHIS assesses the - projected cumulative hydrologic impacts of all anticipated mining operations in the general area of the proposed Foidel Creek underground mine, As discussed below, the general surface water and ground water areas do not coincide (Figure 1). The ground water area is smaller because of structural limitations. Anticipated mining is defined as the existing coal mines, those for which complete permit applications, have been submitted to the Division and leased federal coal for which there is mine plan information available. Coal mining operations in the study area (Figure 2) are summarized in TABLE 5. This assessment is divided into three major subsections: Description of the Hydrologic Environment, Probable Hydrologic Consequences of Mining, and Cumulative Hydrologic Impacts of Mining. Surface and ground water are discussed separately in each subsection. Description of the Existing Environment A. Regional Geology The sedimentary rocks above the upper Yampa River Basin in Hayden, Colorado have been intensely folded and faulted. Trout Creek, Oak Creek and their tributaries flow through a very tightly folded synclinal basin, the Twentymile Park Basin. This folding is related to the uplift of the Park Range to the East and the uplift of the Williams Fork Mountains and White River Plateau to the south. Eight active and reclaimed surface and underground coal mines rim the Twentymile Park Basin, (Figure 3). This structural basin is a sub-basin of the larger Sand Wash Basin. The Twentymile Park Basin consists of a deep central basin flanked by two shallower basins to the north and southwest. The southwestern basin is structurally connected to the Sand Wash Basin by the doubly plunging Hayden Syncline. The Hayden Syncline plunges to the northwest into the Sand Wash Basin and provides a limited outlet to the Twentymile Park Basin. The tight folding of the sedimentary rock strata within the Twentymile Park Basin has resulted in faulting within the basin. The geologic units occurring within the Twentymile Park Basin range in age from Late Cretaceous to Quaternary (Figure 4). The oldest exposed sedimentary rocks are that of the Mancos Shale, which was deposited under marine and near-marine conditions. After deposition of the Mancos Shale, sediments of the Iles and Williams Fork Formations of the Mesaverde Group were deposited mostly in terrestrial environments. Following deposition of the Mesaverde Group, sediments of the Lewis Shale were deposited in a -32-