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Conclusions <br /> Significant incremental flooding hazards from a failure of the Orono Dam are generally limited to <br /> the Elk River between the dam and the Mississippi River, with impacts on the Mississippi River <br /> being confined to the channel at low flows and insignificant during natural flood flows on the <br /> Mississippi. Previous inundation maps for the Orono Dam have suggested a hazard to homes <br /> on the south bank of the Mississippi about 0.25 mile downstream of the confluence. The <br /> analyses reported here suggest that a failure of Orono Dam having significant consequences <br /> along the Mississippi would not coincide with flooding large enough to reach the neighborhoods <br /> in question. Therefore, the Emergency Action Plan should primarily focus on properties along <br /> the Elk River for normal-flow and flood conditions, and incidental users of the Mississippi River <br /> for low-flow conditions. <br /> Finally, the finding described above that the dambreak wave would pass under the Main Street <br /> NW bridge should not be construed to mean the bridge should remain open when a flood <br /> threatens to overtop the dam. The effects of very turbulent flow, debris, and scour cannot be <br /> predicted and closing the bridge and approaches would be prudent. <br /> File:k:\water resource eng\elk river mn\2015 dfa&map\report\report 0320.docx <br /> 7 <br /> 187 <br />