PERMFILE133316 - Laserfiche WebLink

Home Browse Search

This Cumulative Hydrologic Impact Study (CHIS) for a portion of the Yampa River basin has been prepared by the Colorado t4ined Land Reclamation Division • (CMLRD) pursuant to Rule 2.01.6(2)(c). This CHIS assesses the pro,)ected cumulative hydrologic impacts of all anticipated mining operations in the general area of the Hayden Gulch Mine. As discussed below, the general surface water and ground water areas do not coincide (Figure 1). The ground water area is different due to 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 3) are summarized in TABLE 1. This assessment is divided into three ma,)or 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. A. Description of the Existing Environment 1. Regional Geology The sedimentary rocks above the upper Yampa River Basin in Hayden, Colorado have been intensely folded and faulted. Many streams flow through very tightly folded synclines. 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. • Three synclines are of local importance: The Vatering Trough Syncline, the Hayden Syncline and the Twentymile Park Basin. These structural basins are sub-basins of the larger Sand Wash Basin. The Water Trough Syncline and the associated Sage Creek anticline are two north-trending folds which influence ground water flow near the Hayden Gulch Mine. The Twentymile Park Basin east of the Sage Creek anticline, consists of a deep central basin flanked by several shallower basins to the north and southwest. The southwestern portion of the basin is structually connected to the Sand Wash Basin by the doubly plunging Hayden Syncline. The Hayden Syncline ptungs to the northwest into the Sand Wash Basin and provides a limited outlet for ground water from the Twentymile Park Basin. The geologic units occurring within the area region vary 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 predominantly marine environment (USBLM, 19761. Younger sedimentary rocks of the Late Cretaceous and Cenozoic periods do not occur in the Twentymile Park Basin due to erosion or non-deposition. The following description of the geologic units occurring within the Twentymile Park Basin is modified from Warner and Dale (1982) and Brogden and Giles (1977). • -11-