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slope, bedrock dip, erosional patterns, and actual and potential ground <br />failure. Calculations were made of the percent topographic slope for- a+•eas • <br />where failure has occurred, where potential failure may occur, and where <br />failure apparently has occurred in the past but where the slope appears to have <br />stabilized. The results of these calculations and field observations indicate <br />topographic slopes with grades 16% (90) or more appear to be critical. <br />Similarly, predominantly shale sections are prone to failure if their dip is 90 <br />(16% grade) or more, depending on erosional (geomorphic) conditions. Any <br />predominantly shale slope over 16% (90) is likely to fail particularly if the <br />rock dip angle and percent slope are at or about the same magnitude. There <br />probably is an upper limit to this relationship but it has not been determined <br />in this study. Slopes of less than 16% (90) developed on primarily shale <br />bedrock should not fail unless they are subjected to modification that would <br />oversteepen them or• parts of them. <br />Regional dip of the rocks in the vicinity of 005 Gulch (Haul Road G) is <br />between 9o and l00 (16% and 18%) to the west. This dip is reflected in many of <br />the topographic slopes. 'Ahere bedrock of these slopes is underlain pr•imar•ily <br />by shale, unstable conditions are likely to occur. If the topographic slope is <br />greater than the regional (16Yo to 18%) 90-10o dip, slides are more likely to <br />occur than not, depending on the erosional (geomorphic) pattern. Topographic <br />noses appear to be more stable than othe+• geomorphic forms in unstable or <br />potentially unstable ground. <br />These relationships are not absolute; however, they do present criteria of <br />which to be aware in design consideration and in field operations. It is <br />strongly suspected that where failures occur at slope percentages shallower <br />than 15% to 16%, there is an increase in the proportion of shale to sandstone, <br />and possibly an increase in moisture content of the material. These areas can <br />occur wherever the lower part of the Williams Fork Formation is present. • <br />18 <br />