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Option E - Vertical Flat Plate Screens in River General This option involves the construction of a vertical flat plate fishscreen structure upstream from the existing headworks. This will place the structure in the flow of the Colorado River. This location involves additional design challenges that are not as significant as the screen options in the canal downstream from the headworks. These include; fluctuating river water surface elevations, heavy debris loads, possible sedimentation and de-watering for construction. A plan and section ofthis arrangement is shown on Figure 10 and 11 in Appendix B. Photos 13 and 14 in Appendix A show the location of this option. The structure will consist of a concrete slab set on the invert of the river just upstream from the headworks. It will project upstream in the river and be aligned approximately parallel with the right bank. A large excavation of the right riverbank will be required to allow the flow to pass through the screens and then to the existing headworks (see Figure 10). A structural steel column and beam frame system will be attached to the concrete base slab. The columns on the river side of the structure will be equipped with vertical guides to hold the fishscreen panels. A second set of guides downstream from the screen panel guides will be used for panels containing the flow distribution baffles. The invert of the river in front of the headworks varies; for the screen designs it will be assumed to be at approximately El. 4676.0. The base of the screens will be set one foot above this, at El. 4677.0. The minimum depth of flow in the river at the headgates is controlled by the diversion dam and the sluice gates. Figure 4.2c of the Concept Development Report shows the minimum water surface with the sluice gates closed of about E1.4681.0. The minimum depth of flow on the 18 I I I I I I I I I I I I I I I I I I I