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1. the lower Williams Fork <br /> 2. the Twentymile Sandstone <br /> 3. the upper Williams Fork <br /> with individual thicknesses of 920 ft. 100 ft. and 680ft. respectively. The coal seams being <br /> mined at Trapper Mine are all in the upper Williams Fork member and their nomenclature, in <br /> descending order consists of <br /> o F <br /> o G2 <br /> o H <br /> o I <br /> o L <br /> o M <br /> o Q <br /> o Q rider <br /> o R and R rider. <br /> Surface Water Hydrology <br /> Drainages within and adjacent to the permit area (on the north facing slopes), drain south to north <br /> in a dendritic pattern as illustrated in Map 1 above. Drainages flow primarily in response to <br /> snowmelt and/or heavy rains,eventually discharging to the Yampa River. Drainages in the <br /> southern portion of the permit area drain southward to the Williams Fork River. Natural surface <br /> waters are of a calcium-magnesium-sulfate type, with total dissolved solids content commonly <br /> greater than 1000 mg/1 in the smaller streams, and less than 1000 mg/1 in the largest streams. <br /> Total dissolved solids concentrations commonly peak during periods of low stream flows; during <br /> high flows, waters are 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 Formation. <br /> The major alluvial aquifers in the area are associated with the Yampa and Williams Fork Rivers. <br /> Many of the coal seams, discontinuous sandstones, siltstones and some of the smaller alluvial <br /> bodies in the area of the mine are also water bearing. These, however, characteristically contain <br /> insufficient quantities of water to be considered significant aquifers. Of the bedrock aquifers, the <br /> Twentymile sandstone produces the best quality ground water, a bicarbonate-type possessing a <br /> relatively low total dissolved solid content of less than 600 mg/1.Ground water in the White <br /> sandstones contains total dissolved solids generally greater than 600 mg/1 due to high levels of <br /> sulfate and bicarbonate. Ground water in the coal-seam aquifers and interbedded sandstones and <br /> siltstones is commonly of poor quality with total dissolved solids greater than 1000 mg/1 due to <br /> 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 speeds, and high levels of <br /> insolation (exposure to sunlight). The Craig area is in the rain/snow shadow of mountain ranges <br /> to the west and south and consequently has a high number of dry, clear days. <br /> 7 <br />