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• shallow slope failures, erosion-related maintenance problems and increased difficulty <br />supporting vegetation, cut slopes can be as steep as 1.5:1 (overall) where located well <br />above ground water levels in the very stiff to hard clay. Cut slopes should not be <br />allowed to receive surface drainage from above. If possible, uphill drainage should be <br />directed away from the face of cut slopes. Deep cuts should be benched at 8 to 15-foot <br />height increments to help minimize erosion problems. Promoting native-type vegetative <br />cover will decrease the erosion potential of slopes. Ground water and seepage from the <br />face of cuts will decrease the factor of safety, possibly requiring dminage blankets, <br />mechanical slope reinforcement or other methods. <br />(2) Fill slopes should be no steeper than 2.5:1 (horizontal to vertical) overall. However, for <br />slopes where some increased risk of erosion, creep and shallow slope failures can be <br />• accommodated, the overall slope of fills can be increased to 2:1. )f steeper slopes are <br />required, the use of select rock Fill or mechanical stabilization will be necessary. The <br />face of a clay fill slope is expected to creep at an inclination of 2:1, but should not result <br />in a large failure, unless pore water pressures increase. Benching of the Fills is <br />recommended, in order to reduce the potential for face erosion and help promote re- <br />vegetation. <br />In order to utilize a mechanical stabilization technique such as plastic grid sheet to <br />increase safe fill slope inclination, a granular backfill would be necessary to generate <br />friction strength to interact with the grid and form a gravity wall. We assume this <br />backfill would have to be imported to the site. <br /> <br />14 <br />