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<br />-r.. <br /> <br />Mr. Bill Crepeau <br />September 7, 1984 <br />Page three . <br /> <br />Hydrostatic Forces <br /> <br />- <br /> <br />If the island is completely protected with a dike system, <br />the hydrostatic forces which all interior structures, pipelines, <br />manholes, etc., will be subjected to during a flood occurrence <br />must be considered. These horizontal, vertical, and buoyancy <br />forces will have a damaging effect on sub-surface structures and <br />pipelines. <br /> <br />Erosive Forces <br /> <br />The main channel of the Colorado River has shifted and is <br />presently adjacent to the island. This shift occurred during the <br />1983-1984 floods. When the island's stream banks are subject to <br />high flows, severe erosion will occur in the vicinity of the <br />island where the water treatment plant is located. As a result <br />of the 1984 flood, all the natural stream bank armament was <br />washed away. Therefore, any future high waters will actively <br />erode the deteriorating sandbag dike. These erosive forces <br />completely destroyed the downstream portion of the island during <br />the 1984 flood. <br /> <br />Stream Migration <br /> <br />The conveyance channels of the Colorado River are migrating <br />to the north. Today, seventy percent of the mean annual volume <br />flows in the two channels that are adjacent to the island. This <br />migration is due to debris and gravel-bar buildups throughout the <br />floodplain as result of the 1983 and 1984 flooding conditions. <br />With these increased flows adjacent to the island, the Town's <br />water supply will be subject to an increased number of flood <br />risks, annually. <br /> <br />Through the Board's monitoring of the hydraulic <br />characteristics of the Silt reach of the Colorado River, it is my <br />opinion that the life of this island is short! The community's <br />proposal to relocate the plant is a wise one, and I can strongly <br />endorse that option. <br />