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<br />1) Determine where levees are required and their effect on flood elevations, <br /> <br />Note: Information in this report identifies where levees may be considered <br />and the water surface elevation for the lOa-year event. <br /> <br />2) Conduct a detailed soils analysis to determine foundation conditions, <br />seepage potential, se':tlement and slope stability. <br /> <br />3) Identify borrow are,as and provide testi ng to assure suitab"i 1 ity of <br />materi a Is and corrpact ion necessary to control seepage and provi de stab i 1 ity. <br /> <br />4) The general design of the levee wi 11 depend on the above parameters. <br />However, the U.S. Army Corps of Engineers and FEMA recDmmend some general <br />guidelines which include: <br /> <br />a. Provide a minimum of 3.0 feet of freeboal'd for the lOa-year flood event. <br /> <br />b. Provide an addit'onal 0.5 feet of freeboard at the upstream end of the <br />levee and taper to 0.0 additional feet at the downstream end. <br /> <br />c. Provide a minimum of 4.0 feet of freeboard 100 feet upstr'eam and <br />downstream of structures and bridges. <br /> <br />d. Provide a minimum crest width of 10 feet to allow for compaction <br />equipment and maintenance vehicles. <br /> <br />e. Provide a minimLm of 2 feet horizontal to 1 foot vertical side slopes <br />for rip rap p lacem"nt and stabil ity, <br /> <br />f. Provide milder side slopes for grasslined areas based upon soil <br />stability and velocities adjacent to the levee. <br /> <br />DAM FAILURE ANAlYSIS <br /> <br />A general "dam failure" anilysis was completed 1'01' several reservoirs within the <br />Co I orado River system up stream of the City of Grand J unc t i on, Co 1 orado. The <br />purpose of this analysis is to estimate the impact.s that an IJpstream dam failure <br />may have on the City of I;rand Junction and to predict the travel time of the <br />ensu'ing flood wave to re"ch the city. The flood impact of a dam failure will <br />depend on the magnitude of discharge already in ~he river at the time of <br />failure. Therefore, an estimate of the increase in flow depth with a dam <br />failure must be made based upon the existing river levels. <br /> <br />11 <br />