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Coal Seam Stratig_raphy <br />The Williams Fork Formation is stratigraphically subdivided into three units or members. These <br />are, in ascending order, the lower Williams Fork, the Twentymile sandstone, and the upper <br />Williams Fork, with individual thicknesses of 920 ft., 100 ft., and 680 ft., respectively. The coal <br />seams being mined at Trapper Mine are all in the upper Williams Fork member and are called, in <br />descending order, the H, I, L, Q, Q- rider, R and R- rider. <br />Surface Water Hydrology <br />Drainages within and adjacent to the permit area (on the north facing slope) run south to north <br />down the slope in a dendritic pattern. Within the permit area are portions of the following <br />drainages, listed from west to east: Buzzard, Coyote, No Name, Johnson, Pyeatt, Grouse, Sage, <br />Oak and Flume. These drainages flow primarily in response to snowmelt and /or heavy rains. <br />All of these drainages eventually discharge into the Yampa River. Drainages in the southern <br />portion of the permit area drain southward to the Williams Fork River. These drainages include <br />the upper portions of Ute, Castor, Deer, Elk and Horse Gulches. Natural surface waters are of a <br />calcium- magnesium - sulfate type with total dissolved solids content commonly greater than 1000 <br />mg /l in the smaller streams and less than 1000 mg/l in the largest streams. Total dissolved solids <br />concentrations commonly peak during periods of low stream flows; during high flows, waters are <br />diluted resulting in low concentrations. <br />Ground Water Hydrology <br />Within the general area of the Trapper Mine, ground water exists in both bedrock and alluvial <br />aquifers. Significant bedrock aquifers are the Trout Creek, Middle, Twentymile, and White <br />sandstones. The Middle, Twentymile and White sandstones lie within the Williams Fork <br />Formation; the Trout Creek sandstone is the uppermost member of the underlying Iles <br />Formation. The major alluvial aquifers in the area are associated with the Yampa and Williams <br />Fork Rivers. Many of the coal seams, discontinuous sandstones, siltstones and some of the <br />smaller alluvial bodies in the area of the mine are also water bearing. These, however, <br />characteristically contain insufficient quantities of water to be considered significant aquifers. <br />Of the bedrock aquifers, the Twentymile sandstone contains the best quality ground water, a <br />bicarbonate -type water with a relatively low total dissolved solid content of less than 600 mg /1. <br />Ground water in the White sandstones contains total dissolved solids generally greater than 600 <br />mg /l due to high levels of sulfate and bicarbonate. Ground water in the coal -seam aquifers and <br />interbedded sandstones and siltstones is commonly of poor quality with total dissolved solids <br />greater than 1000 mg /l due to high levels of bicarbonate and sodium. <br />Regional Climate <br />The region has a highland continental climate characterized by low precipitation, large <br />fluctuations in diurnal temperatures, low humidity, moderate wind, and high levels of insolation <br />(exposure to sunlight). The Craig area is in the rain /snow shadow of mountain ranges to the west <br />and south and consequently has a high number of dry, clear days. <br />Trapper Mine 12 July 9, 2013 <br />