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<br />Town of Greybull Levee Protection <br /> <br />In August 1998 the Wyoming National Guard, 133rd Engineering Company <br />completed a streambank stabilization project adjacent to the Town of Greybull, <br />Wyoming on the Big Horn River The streambank in front of a levee protecting the <br />town was eroding away. The erosion occurred during spring high water. The Big Horn <br />River is regulated by the Boysen Reservoir 85 miles south of Greybull. <br /> <br />During periods of excessive spring runoff, the river level has come within ten inches of <br />overtopping the levee. The streambank is composed of mostly sand, with the <br />remainder comprised of a silt/ clay mix. In preceding years, the river flow had created <br />a gravel bar which was channeling the flow toward the bank in front of the levee. The <br />bank was eroding at the rate of approximately 8 to 10 feet annually. <br /> <br />The U. S. Army Corps of Engineers, Omal1a District Hydrologic Engineering Division <br />recommended construction of a jetty system to move the river back from the levee. <br />Since the water often reaches or exceeds the bank top elevation, the sides and top of <br />the jetties are constructed of rock. This construction should permit the high water to <br />flow over the jetties and still push the current far enough into the main channel to <br />attack the gravel bar. A twenty foot shift in channel flow would match the anlOunt of <br />bank loss documented over recent years. In addition to adding to the overall stability <br />of the bank, the channel movement might reduce the effect of high water along the <br />bank seeping Into a gravel vein which runs under the levee. The water seepage does <br />not pose a structural problem for the levee, but the water floods basements in the area. <br /> <br />Plarming for the jetties construction project began in September 1995. The Town of <br />Greybull purchased all the material utilized to construct the jetties and the Wyoming <br />National Guard, 133rd Engineering Company constructed the jetties. This mitigation <br />project has an estimated value of 5300,000. No FEMA funding was utilized in this <br />project. <br />