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To prevent fish entrainment at the Tracy Pumping Plant, the Tracy Fish Collection Facility (TFCF) was designed to guide fish along a diagonal line of louvers into one of four primary bypass intakes. Replacement primary bypass intakes and transition boxes with a new tapered choke design were installed in 2004 to improve hydraulic conditions for fish collection. The replacement intakes were developed in the laboratory for an expected range of field operating conditions. Hydraulic field evaluations were conducted to verify the performance of the new intakes. Velocity profiles were collected in the intake entrance and upstream of the intakes to document velocity field distributions.

Results show that common field conditions such as bypass ratios less than 1.0 and high debris loads adversely affect bypass performance by degrading uniformity in the vertical velocity profiles at the bypass entrances. Such uniformity is considered a performance indicator from past studies connected with fish salvage efficiency. Facility operation with bypass ratios greater than 1.0 provides the best hydraulic conditions for efficient fish collection by minimizing flow disruption and eddying and promoting smooth flow acceleration into the intakes. Since debris can affect approach velocity distributions, debris fouling on the trashrack and louvers should be minimized.

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