GENERAL38637 - Laserfiche WebLink

Home Browse Search

Coal Seam Stratiora~hv The Williams Fork Formation is stratigraphically subdivided into three units or members. These are, in ascending order, the lower Williams Fork, the Twentymile sandstone, and the upper Williams Fork, with individual thicknesses of 920 ft., 100 ft., and 680 ft, respectively. The coal seams beine mined at Trapper Mine aze all in the upper Williams Fork member and aze called the H, I, L, Q, Q-rider, R and R-rider. Surface Water Hydrolo,,ny Drainages within and adjacent to the permit area (on the north-facing slope) run south to north down the slope in a dendritic pattern. Within the permit azea are portions of the following drainages, listed from west to east: Buzzazd, Coyote, No Name, Johnson, Pyeatt, and Flume. These drainages flow primarily in response to snowmelt and/or heavy rains. All of these drainages eventually discharge into the Yampa River. Drainages in the southern portion of the permit azea drain southward to the Williams Fork River. These drainages include the upper portions of Ute, Castor, Deer, Elk and Horse Gulches. Natural surface waters aze of a calcium- magnesium-sulfate type with total dissolved solids content commonly greater than 1000 mg/l in the smaller streams and less than 1000 mg/l in the lazgest streams. Total dissolved solids concentrations commonly peak during periods of low stream flows; during high flows, waters are diluted resulting in low concentrations. Ground Water Hydrology Within the general azea of the Trapper Mine, ground water exists in both bedrock and alluvial aquifers. Significant bedrock aquifers are the Trout Creek, Middle, Twentymile, and White sandstones. The Middle, Twentymile and White sandstones lie within the Williams Fork Formation; the Trout Creek sandstone is the uppermost member of the underlying Iles Formation. The major alluvial aquifers in the azea are associated with the Yampa and Williams Fork Rivers. Many of the coal seams, discontinuous sandstones, and siltstones and some of the smaller alluvial bodies in the area of the mine aze also water bearing. These, however, chazacteristically contain insufficient quantities of water to be considered significant aquifers. Of the bedrock aquifers, the Twentymile sandstone contains the best quality ground water, a bicarbonate-type water with generally a relatively low total dissolved solids content of less than 600 mg/1. Ground water in the White sandstones contains total dissolved solids generally greater than 600 mg/l due to high levels of sulfate and bicazbonate. Ground water in the coal-seam aquifers and interbedded sandstones and siltstones is poor quality commonly with total dissolved solids greater than 1000 mg/I due to high levels of bicarbonate and sodium. Resional Climate The region has a highland continental climate characterized by lo~v precipitation, large fluctuations in diurnal temperatures, low humidity, moderate wind, and high levels of insolation T.:apoe: Mane Mav 1~ .~oa