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This opinion is based mainly on a cursory examination, without special or ~ <br />detailed study. <br />4.1.2 Twentymile Sandstone and Above. The Twentymile Sandstone forms a <br />prominent bluff on the north side of 005 Gulch. This massive sandstone is at <br />the base of the upper part of the Williams Fork Formation. The contact of the <br />base of the Twentymile Sandstone was generally mapped north and south of 005 <br />Gulch by photogeologic methods. Neither of the planned engineering units in <br />this project are included within the Twentymile Sandstone and overlying rocks. <br />4.2 Structure <br />The general structure was mapped photogeologically to determine if there <br />were any anomalous conditions that might be related to ground stability in the <br />area. Strike and dip of the rocks is shown on Drawings 9111-1 and 9111-2, <br />although the amount of dip is not indicated. The amount of dip generally <br />averages about loo to the west and northwest since the area is located on the <br />western flank of the Sage Creek anticline. <br />Abnormally steep dips of 32o and 47o and one reverse dip of 29o are mapped <br />in and adjacent to unstable and potentially unstable ground between Sta. 65+00 <br />and Sta. 73+00, left. These dips may be on large masses of rock that appear to <br />be in place, but have been moved by erosional processes and possibly by <br />slumping. <br />Two faults are mapped in the south half of sec. 10, T.5N., R.88W. These <br />faults are not as easily observed on the ground as they are on the aerial <br />photographs. The faults do not have any apparent adverse effect on the ground <br />stability either in 005 Gulch or• in the area adjacent to it. <br /> <br />8 <br />