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1 I Figure 1-1. Example Modified Inclined Screen STOPL SLOT FlSH BYPASS 9 60 0 SOLID MATE ? -? ~ P1AW I ;; STRU SSUPPO? 7777 . .1 m WITH A IS• INCLINED SCREEN SEMON TRAM BACK Pull BYPASS `Ir 1 0.6 m INCLINED SCREEN e + --? s- SOLID PLATB 14 m WITH A 13• INCLINED SCREEN _ CAM (Source: Taft et al. 1995) 1.3.4.2 Eicher Characteristics. The Eicher screen is a developing technology that is intended to divert fish at significantly higher approach velocities than conventional screen designs. It is named after biologist George Eicher who first developed the idea in the late 1970's as a better means of safely bypassing fish around a turbine. The basic Eicher screen is elliptical in shape and designed to fit inside the pressure penstock at an incline to flow (Figure 1-2). Non-penstock designs are also being developed. Fish are diverted up to the penstock roof where a bypass conduit is located. Rather than being designed to guide all target fish to a bypass without contact with the screen, the screen is constructed of very smooth stainless steel profile wire to minimize injury to fish that contact the screen. Debris is removed by rotating the screen about a pivotal shaft which allows flow across the reversed screen surface. During debris flushing, fish escapement may occur. This screen has been shown to operate successfully under a range of velocities up to a maximum of about 8 ft/sec. It is relatively less expensive and has smaller space requirements than most current barrier screen designs. Since it is installed in the penstock, forebay area is not required, nor is icing a problem. In addition, since the screen operates at much higher velocities, predation of bypassed species is reduced. Head loss may be significant (up to 2 feet) due to high velocities and baffling needed to obtain uniform flow. During backflushing, the flow distribution into a turbine may be affected. Control Structure Feasibility Evaluation 1-$ Miller Ecological Consultants, Inc., February 18, 1997