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<br /> <br />, <br /> <br />OO~3D~ <br /> <br />A freeboard of 6.'; feet was provided in the original designs prior to the <br />revisions in the Spillway design, but was later reduced to 5.8 feel. Factors influenc- <br />ing wave heigh! and wave ride-up. including maximum wind velOCity, its direction and <br />duration, offshore reservoir depths, fetch, slope of dam and shore, and the nature of <br />the surface protection. were Considered in selection of the required freeboard. The <br />reduction in freeboard (rom 6.4 to 5. 8 feet was considered permissible on the basis <br />that the sluice....'ay opening and operation had been modified and that the reservoir would <br />be at the maximum water surface for only a short period of time if the design rlood <br />OCCurred. <br /> <br />To provide for future settlement of the foundation and eonsolidation of the em. <br />bankment without a reduction in freeboard a camber was provided over the crest length. <br />Camber was varied (rom a maximum o( 1. 5 (eet by three vertical parabolic curves to <br />provide for the anticipated settlement and consolidation o( varying magnitude at differ_ <br />ent locations. Provisions were made for COvering the crest of the dam with 8 inches of <br />gravelly material, tapped with 4 inches of gravel surfaCing. Wood posts with guardrails, <br />conforming to State highway requirements, were adopted to provide safe travel over the <br />dam crest. <br /> <br />A cutoff trench was provided upstream from the Centerline o( the dam, exca. <br />Vated to a suitable and reasonably impermeable stratum. A pervious filter blanket, <br />designated as Zone 2, lOcated a minimum distance of 110 feet downstream from the <br />centerline of the dam, was provided to intercept seepage through the embankment and <br />to lower the saturation line at the downstream portion of the embankment. At the <br />lower end of the downstream toe and contiguous with the pervious blanket, provision <br />was made for Zone J, which Would be constructed of selected material from the dam <br />foundation and structure excavations. <br /> <br />The Upstream siope was designed with a 20.foot berm (fig. 5), located at an <br />ele~'alion just below that of Ihe minimum water surface. The slope immediately above <br />the berm was established at 3 to 1 to within 32 (eet of the crest, and the remainder of <br />the slope to the crest was steepened co 2-1/2 to 1. The slope was protected with 3 (eet of <br />rock riprap placed on an 18-inch gravel or crushed-rock blanket to an elevation 3 feet <br />above the normal water surface, diminiShing to 2 feet of riprap on a 12-inch blanket at <br />the dam crest. The toe of the dam below the berm .....as flattened to an 8 to 1 slope. <br />Provision was made on the outside of this slope for dumping material obtained from ex- <br />ca~'ation (or the dam foundation, Spillway, and outlet works. <br /> <br />Two 10.foot berms ....ere lOcated at the downstream slope changes to collect <br />rainfall runoff, reduce erosion to a minimum, and prOVide approaches for vehicles to <br />irrigate the seeded areas. Lower down, a 20.foot berm was provided for the installa_ <br />tion o( the Hale ditch outlet pipe. The downstream slopes were flattened progressively <br />....'Hh distance down.....ard (rom the crest, as shown on figure 5. <br /> <br />The superimposed ....'eight of the rock riprap and free.draining gravel or <br />crushed.rock blanket on the embankment material of low permeability introduces suffi~ <br />dent resistance to movement of the fine material during reservoir drawdo'\O.n to prevent <br />displacement. The blanket acts as a filter and the rock riprap protects the slopes <br />against damage from wave action. <br /> <br />The rock for riprap was required to have a specific gravity of not less than <br />2.60 so that riprap of sufficient weight to withstand the antiCipated ....a\'e action would <br />be obtained. A provision was also made that not more than 25 percent of the riprap <br />material should Consist of pieces smaller than 1,2-cubic.fOOt size, and at least 30 <br />percent should consist of pieces larger than 3-cubic-(oot size. TOt' trenches at the <br />base o( the riprap in both abutments, filled with rock riprap to a minimum depth of 5 <br />feet, ....ere provided to preVent undermining of the riprap base by ....ave action. To <br />further stabilize the abutments above the berm and adjacent to the Upstream toe, rock <br />groins, 100 feet long spaced at 200-foot centers. were placed on the original grOund <br />surface immediately upstream from the dam. <br /> <br />Toe drains were provided near the outer limit of the downstream section of the <br />embankment to facilitate egress of seepage water and thus prevent impairment to the <br /> <br />17 <br /> <br /> <br />--- <br /> <br />- <br /> <br />- <br /> <br />