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1 <br /> (mechanical cleaners, bypasses, etc.) begin to reduce some of the economy of high velocity screens. <br /> Screens with velocities up to and including 3 to 5 ft/sec have wide application in water and <br /> wastewater treatment facilities where debris collection or exclusion is the primary function. <br /> Facilities intended to function with velocities greater than 5 ft/sec are rare and mostly experimental. <br /> High velocity screens tend to have the same open spacing as low velocity screens. If fish mortality is <br /> <br />t an acceptable, albeit regrettable, consequence of downstream passage restriction in the present study, <br />the relative economy of high velocity screens may make them a particularly interesting alternative. <br />1.3.3.4 Behavioral <br /> Behavioral devices have been used for protection at dams and diversions for decades (Molting 1961, <br /> Fish Passage Technology 1995). The purpose of behavioral devices is to elicit a response either <br /> away from harm or towards a safe fish bypass at each of these facilities. Behavioral methods include <br /> a wide range of applications including electrical, lights and sound as well as several other behavioral <br /> devices. These three major types are described in more detail in immediately following sections of <br /> this narrative. The electrical methods and lights and sound try to elicit a startle response at the <br /> facilities although no success has been shown in causing movement to a desired location or in a <br /> desired direction in a consistent manner. Behavioral methods may not be able to direct fish to a <br /> bypass when the bypass flow is small compared to river flow. These are some of the limitations for <br /> behavioral methodologies. In addition, the behavioral methods only work on actively swimming life <br /> stages. Passive life stages are not deterred by behavioral devices. Features of these behavioral <br /> devices are summarized in Table 1-2. <br />1.3.3.5 Other Technologies <br /> Other technologies available are generally grouped with the behavioral devices. These include air <br /> bubble curtains, hanging chains, water jet curtains, chemicals and visual keys. There' have been no <br /> recent advances in these techniques and limited success in the use of these techniques at the facilities <br /> where they were used. Most of these would be used in conjunction with some other type of <br /> screening or passage facility and they would not be the primary technology used to safely bypass fish <br /> or deter fish from movement downstream or upstream. None of these technologies had direct <br /> application at either of the projects, Elkhead or Highline Reservoir, and therefore, not discussed in <br /> detail in this report. <br />1 <br />1 <br /> <br />Control Structure Feasibility Evaluation 1-4 <br />Miller Ecological Consultants, Inc., February 18, 1997