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Williams Fork consists of alternating beds of sandstone, sandy shale, carbonaceous shale and <br /> coal. The coal to be mined lies within a 392foot interval in the Fairfield Member of the Williams <br /> Fork Formation. The quality of the coal seams is midway between bituminous and subbitummous. <br /> Underlying these coal beds are 9,000 feet of Mesozoic and 4,500 feet of Paleozoic sediments. The <br /> Williams Fork Formation is estimated to be 1,600 feet thick in the permit area and is underlain by <br /> the ridge forming Trout Creek Sandstone member of the Iles Formation. <br /> Overburden material consists of a sequence of sedimentary claystones, siltstones, shales and <br /> carbonaceous silty shales. These sediments are typical of the cyclothems deposited along the <br /> western interior of North America during the Late Cretaceous time. The site specific stratigraphy is <br /> described in Exhibit 6 and on Map 8 of the PAP. There are four coal seams below the "F" seam <br /> which cannot be economically mined by surface mining methods. <br /> Results of test borings are included in Section 2.04.6 of Volume 1 (East and West Pit), Volume 12 <br /> (South Taylor Pit and Lower Wilson Area), and Volume 15 (Collom Pit) of the PAP. Test borings <br /> resulted in information on the presence of subsurface water, characterization of the physical <br /> properties of the overburden, and testing and evaluation of the geochemical properties of the <br /> overburden. <br /> 3.2.6 Climate <br /> Climatic information is found in Section 2.04.8 of Volume 1 of the PAP. The region is <br /> characterized by a semiarid steppe climate regime. Precipitation averages 18 inches per year with <br /> a significant portion of this yearly precipitation occurring as snowfall. Prevailing winds over the <br /> permit area are from the southwest and average eight to nine miles per hour. High winds are not <br /> common due to the protection afforded by local terrain. <br /> 3.2.7 Soils <br /> Soils information is found in Section 2.04.9 of Volume 1, Volume 12 and Volume 15 as well as <br /> Exhibit 9 of the PAP. The most prevalent soils, including Burnette, Work, Lamphier, Rhone, and <br /> Northwater Loams, are mollisols of the suborder boroll, which developed from residuum or <br /> colluvium on gently sloping to rolling ridgetops, moderately steep side slopes, and in gently <br /> sloping, concave narrow stream valleys. Shallow, rocky soils of the order entisol occur to a limited <br /> extent within the area to be disturbed on steep, south facing slopes. The very thick Silas loam soil, <br /> developed from alluvium, is found within narrow bands along the larger ephemeral drainages. <br /> The predominant hill-slope soils have relatively thick, loamy textured mollic epipedons,well suited <br /> for reclamation use. Salvageable thickness of these soils average from 12 inches to 30 inches. <br /> Subsoils in these units are somewhat marginal due to heavier texture or excessive cobbles. The <br /> Silas loam soil along the drainage valley bottoms is generally suitable for salvage to depths of five <br /> feet or more. <br /> 3.3 Ground Water Hydrology <br /> Ground water information is found in Sections 2.04.5, 2.04.7 (Volume 1 for the East Pit, West Pit, <br /> 16 <br /> Permit Revision No.5(PR-05),C-1981-019 <br />