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• area. The overall average maximum overburden thickness in the proposed 5-year mining area is between 600 ft and 700 ft. 3.2.2.2 Surface Topography The surface topography in the proposed permit area is illustrated on Map A. The development of the topography is controlled by the geologic framework, the Colorado River, South Canyon Creek and Alkali Creek. The Grand Hogback, locally named Coal Ridge, is the major topographic element in the permit area and the proposed 5-year mining area. The Grand Hogback trends roughly east-west across the mining area, turning southward at South Canyon Czeek near the eastern edge of the proposed permit area. Coal Ridge rises abruptly from an elevation of 5800 ft at the base of the hogback to elevations along the ridge from 6800 ft near the western edge of the proposed permit area to a maximum of 8273 ft at Horse Mountain. From the ridge crest, the hogback dips gently downward to the south toward Alkali Creek, generally • subparallel with the dip of the strata. This side of the ridge is characterized by numerous deep gullies which drain into Alkali Creek. The proposed 5-year mining area lays under the ridge crest of Coal Ridge. Surface elevations vary from 6300 ft near the west end of the mining area to 7900 ft near Horse Mountain. 3.2.2.3 stratigraphy The general stratigraphy of the permit area is described in Section 3.3.2 of the permit application. This section presents the pertinent aspects of the site stratigraphy as they relate to subsidence and surface subsidence effects. The stratigraphic section above the mine includes soil overburden and rock overburden. Soil overburden. The soil overburden in the proposed permit area is generally thin and restricted to valley and gully bottoms or the dip slope of Coal Ridge. Ridge crests tend to be rock outcrops. page 15