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<br />G021~5 <br /> <br />, <br />~ <br />u <br /> <br />Concern: <br /> <br />, <br />I <br />i <br />~ <br />c <br /> <br />2.2.4 Levee and Diversion Structure for the West Side Ditch <br /> <br />r <br />~ <br /> <br />During the flood, a low dam and an earthen jetty which <br />constitutes the diversion structure for the West Side Ditch <br />failed. There is concern that the destroyed diversion <br />structure poses a threat to the levee system, <br /> <br />Findings: <br /> <br />The West Side Ditch has private water rights totalling <br />34.6 cfs, An earthen jetty extends from the north bank into <br />the channel to force low flows towards the point of diversion <br />on the south bank. A low (collapsible) dam was used to raise <br />water in the channel to a sufficient height (7535.0 feet) to <br />enable the ditch to physically divert the decreed water from <br />the river. During the flood the jetty was over topped and <br />washed out in two locations, The low dam also collapsed. <br /> <br />" <br />e <br />" <br /> <br /> <br />I <br /> <br />The existence of this diversion structure, and that of a <br />similar structure for Chicago Ditch just downstream, is a <br />significant obstruction to flows between the levees, These <br />diversion structures, in combination' with the railroad bridge, <br />the willows and other vegetation in the channel cause an <br />increase in flood heights which put further stress on the <br />levees upstream of the ditches. <br /> <br />I <br /> <br />Elimination of, the approximately 800 foot long jetty <br />with either a better designed inlet structure and/or an <br />alternate point of diversion would significantly improve the <br />conveyance capacity of the channel, The volume of the jetty <br />is estimated at 800 x 26 x 7 = 5,393 cubic yards. <br />27 <br /> <br />Periodic removal of the willows from the channel would <br />also significantly improve the channel conveyance capacity. <br /> <br />Cost Estimates: <br /> <br />To remove existing jetty and <br />diversion structure <br />5393 cu/yd x $4.00/cu/yd = <br /> <br />$ 21,572 <br /> <br />6 <br /> <br />To construct a new diversion <br />structure' <br />10,000 feet x $15/ft <br /> <br />= $150,000 <br /> <br />15,000 <br />$186,572 <br /> <br />$ 20,000 <br /> <br />r <br /> <br />Engineering at 10% <br />Subtotal <br /> <br />1'0 remove willows in this reach <br /> <br />77 <br />