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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/l. Ground water in the White <br /> sandstone 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/l 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 /> Local Climate <br /> The climate of the Craig, Colorado area is characteristic of semi-arid steppe regions. Average <br /> annual precipitation for the town of Craig, six miles north of Trapper, is 13.5 inches, of which <br /> over one third is snowfall (averaging 66.5 inches/year). Trapper Mine's average annual <br /> precipitation is 16.7 inches. Mean annual temperature in Craig is 437, with recorded extremes <br /> of-45°F and 100'F. Winds predominate from the west, but are locally modified by topographic <br /> features. The growing season for the area in the vicinity of Craig averages 77 frost-free days. <br /> Soil Types, Characteristics and Distribution <br /> Three soil orders are found in the permit area: <br /> 1 . Aridisols <br /> 2. Entisols <br /> 3. Mollisols. <br /> Characteristic of fairly steep, semi-arid regions of northwestern Colorado,they represent soils <br /> grading from recently developed soil bodies with minimum horizon development (Entisols) to <br /> older soils comprising well defined diagnostic horizons (Mollisols). Overall, the soils found in the <br /> permit area are relatively deep and well drained exhibiting effective rooting depth ranges from <br /> two to sixty inches. The deepest soils yielding the greatest rooting depths occur in valleys and on <br /> the leeward sides of ridges. Soil reaction is slightly acid to moderately alkaline over the permit <br /> area with the exception of inclusions of small scattered areas with saline substrata. These small <br /> areas have probably formed in place from weathered sodic shale. <br /> Vegetation Distribution <br /> Vegetation in the area grows largely in response to macro-climatic influences of the region. The <br /> north-facing slopes, having moderate to deep soils characterize a relatively mesic moisture regime <br /> and favorable levels of insolation throughout the year, exhibit well-developed mountain shrub <br /> communities. On colluvial toe slopes, communities dominated by sagebrush and grasses occur. <br /> 9 <br />