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The one alluvium fan deposit large enough to be mapped in this project is <br />generally between Sta. 33+00 and Sta. 41+00 where the haul road alignment <br />passes through the lower part of the unit. Material in the alluvial fan <br />probably will be poorly sorted as compared with stream alluvium (Q+jl). It is <br />easily conceivable that scattered boulders larger than three feet in maximum <br />dimension could be found in this deposit. <br />4.3.2 Deposits Related to Weathering Processes. The following <br />descriptions relate to units that are unstable and potentially unstable. These <br />units are formed by weathering of bedrock in Quaternary time in the lower part <br />of the Williams Fork Formation. The nature of movement and potential movement <br />is such that these units may be categorized by age, from the youngest (Qpug) to <br />the oldest (Qsg). <br />Potentially Unstable Ground (Qpug). Occurs primarily in sections of the <br />lower part of the Williams Fork Formation where marine shale is the predominant <br />rock type. Characteristics on the aerial photographs, field observation, and <br />topographic slope indicate a potential for this material to move under the <br />influence of gravity, particularly in the presence of water. <br />On the aerial photographs certain slopes were included in this unit <br />because of their appearance, similarity, and proximity to areas of unstable <br />ground. <br />This mapping unit was first defined in the photogeologic evaluation <br />because of its appearance and relationship to areas of known unstable ground. <br />The main area of potentially unstable ground occurs from Sta. 49+00 left to <br />slightly beyond the end of the Haul Road G. alignment. Isolated within the <br />boundaries of this unit are areas of observed unstable ground which would be <br />classified as landslides. In the lower part of the Williams Fork Formation <br />there appears to be a genetic relationship between potentially unstable ground <br />and existing unstable ground. <br />10 <br />