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• 28 and 48 feet above the toe, respectively The OSM regulations <br /> require that terraces be pla(-ed at intervals of 50 feet <br /> vertically, to help control drainage and ei osion. The terraces <br /> shown on the sections pro,,-ided to L,incr.)1.-i-Devor_e were spaced <br /> much closer, w1ii.ch pr_es;) .ably w.111 res•..lt in an ix.pr_ovt-R:ent of <br /> drainage cot-iditlons . For p.irposes of stability analysis, the <br /> terraces were placed at locations sho,,m on the preliminary sections <br /> provided to Lincol-i-DeVore. Normally, it is necessary to provide <br /> sufficient width of the terraces to per:r:it clearance for bull- <br /> dozers and other grading equipment . Therefore, a width of 10 feet <br /> was selected for the analysis . <br /> The maximum gradient for the top of <br /> the fill is 50/5, as specified by OSM regulations. This va1•ae wa.i <br /> used in modeling the slope for the analysis . As a minimum gra- <br /> dient for the top of the fill, we recom:rend 2A, in order to in- <br /> sure adequate d_ainage. <br /> Since positive drainage around the <br /> fill will be required, and the underlying native material is re- <br /> latively perir.eable, fully drained conditions we,•e assi ',ed, and no <br /> - ph.reatic line was included in the yodel. <br /> The above considerations for face slc•pe, <br /> terraces, slope height, gradient at the top of the fill, etc. , <br /> were used to provide a geoTetric model of the proposed fill slope. <br /> This is shown for the 2 - 1 slope on plate 1. For the 2. 5 : 1 and <br /> 2. 8 : 1 slopes , the geometry is similar, with the only difference <br /> being the angle of the slope face. <br /> -5- <br />