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I I I I I I I I I I I I I I I I I I I that would deposit at the screens and block the screens and cleaner. If this option were selected for final design, consideration should be given to a sedimentation study of this reach of the river. The cost estimate for this option will include the cost for providing a type of sediment flushing system to attempt to move sediment away from the base of the screens. The system will be assumed to consist of either a pumped water spray or a compressed air with an air-burst system. Either method will involve placing a pipe with nozzles below the base of the screens to move sediment away from the screens. Another feature with this option is the trashrack that extends from the upstream end of the screen structure and angles downstream at a 30 degree angle to the screens and terminates at the diversion dam. The trashrack structure is angled downstream to attempt to deflect and assist the movement of debris in a downstream direction. The trashrack will be cleaned by an automated "'" A e "" trashrake. This was used rather than manual raking because with1Iie rack is placed out in river large debris would be difficult to remove by hand. The deck of the trashrack will be at E1.4690.0, which is above the 50-year flood water elevation. The bars on the trashrack will be assumed to be at 4 inches on center to allow for the passage of fish. This option will also involve the construction of a cofferdam in the river to enable de-watering in the area of the screen and trashrack structures. The construction of the screens will be required to occur during the non-irrigation months of November through March. Table 3.3 on page 12 of the Concept Development Report shows the Monthly Mean Maximum Flow for these months to be 2,859 cfs. The cofferdam will be sized for a water surface elevation in the river resulting from a 21