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,• <br /> <br />below the coal zone, is the 100 foot thick ledge forming Twentymile <br />Sandstone. The Twentymile Sandstone outcrops below the southern end of the <br />mine site. <br />The Twentymile Sandstone and lower lying Trout Creek Sandstone are aquifers of <br />significant regional extent. Other ground water bearing zones occur in the <br />coals and local lenticular sandstones within the mining area. Recharge areas <br />for most of these strata are on the south facing slopes along the Williams <br />Fork River Valley south of the mine. Ground water tends to flow along the dip <br />of the strata (northeast) and some of the localized lenticular sandstones <br />discharge in the form of springs north of the mine. <br />Within the permit area are portions of the Hayden Gulch, Dowden Gulch and Dry <br />Creek drainage basins. The majority of the mine area occurs within the Hayden <br />Gulch drainage. These basins contain ephemeral streams which respond <br />predominantly to spring runoff from snowmelt. Hayden and Dowden Gulch are <br />tributaries to the Williams Fork River which is perennial in nature. <br />The region is characterized by a semi-arid steppe climatic regime. The <br />prevailing wind is from the west and southwest and average annual <br />precipitation is 16.1 inches. The growing season in the region varies from 28 <br />days to 94 days; the time span depends greatly upon the elevation of a given <br />area. <br />Soils at the mine site are of the order moilisol and suborder boroll. These <br />are soils formed in cool climates which are characterized by a very dark <br />colored base-rich surface layer. Variability of the characteristics of the <br />soils on the permit area is primarily due to slope, aspect and topographic <br />position. Deeper soils are located in the valley bottoms and footslopes while <br />the shallower soils occupy the upslopes. <br />Vegetation is also distributed in response to the micro-climatic influences of <br />the north-south,trending ridge and valley complex within the area. Sagebrush <br />communities dominate the richer, deeper soils of the valley bottoms and gentle <br />slopes. Oak communities dominate the generally drier south and west facing <br />slopes in the area, and often intergrade into the other communities in the <br />form of patches of dense oak growth. Aspen dominated communities are found in <br />clumps in small hillside swales and gentle north slopes in the permit areas; <br />these areas are characterized by a more me sic moisture regime and more fertile <br />soils. The remaining mountain shrub can be subdivided into two <br />distinguishable components; communities dominated by chokecherry, and <br />communities dominated by serviceberry. Serviceberry communities are found <br />dominating steep south facing slopes in the southern portion of the mine <br />permit area. These areas are characterized by a relatively xeric moisture <br />regime and poorly developed soils receiving large amounts of high intensity <br />solar radiation. Chokecherry communities are found on the gently sloped hill <br />tops in the area. These communities intergrade with the aspen, sage, and oak <br />communities. <br />-4- <br /> <br />