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-13- <br />• <br />constructed by excavating a trench approximately 12 feet deep through <br />the valley bottom. The trench should be a minimum of 50 feet wide at <br />the base with side slopes of 1:1 or flatter as necessary to maintain <br />stability during construction. The bottom of the trench should be <br />dewatered temporarily during construction. Spoil should be compacted <br />to a minimum of 90 percent of modified Proctor density to construct the <br />stabilizing toe. After the stabilizing toe has been constructed, the <br />remaining fill should be placed in loose lifts ranging from 2 to 3 feet <br />in thickness and compacted using loaded haul equipment. If large boulders <br />occur in the fill, the boulders can be broken down with a grid roller <br />or segregated to the outermost portions of the fill to form a rock shell, <br />which is highly pervious at the downstream edge of the fill. For the <br />• portions of fill underlain by these softer soils, we recommend a maximum <br />slope of 3:1 (horizontal to vertical). <br />LIMITATIONS <br />The recommendations presented in this report are based on testing <br />of specific materials, samples obtained from the haul roads, as well as <br />observations from borings collected from numerous locations along and <br />near the roads and at other locations on the Energy Fuels site. Varia- <br />lions in subsurface conditions can, and do, occur. As the construction <br />process proceeds, we recommend that the compaction of soils to support <br />the haul roads be observed on a periodic basis and the foundation <br /> <br />