Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 7311
Title: Biological evaluation of the prototype gatewell lift-tank system at Lower Granite Dam, 1994
Author/Editor: George A. Swan, M. B. Eppard, P. A. Ocker, Robert N. Iwamoto, Benjamin P. Sandford
Publication Year: 1994
Publisher: National Marine Fisheries Service
Contracting Agency: U.S. Army Corps of Engineers. Walla Walla, Washington
Contract Number: E86940120
Date: 1994

A proposed drawdown of Lower Granite Reservoir would reduce turbine intake gatewell water levels at the dam to an extent that would prevent normal egress of migrant salmonid smelts to the fingerling bypass collection gallery.  This could result in large numbers of fish stranded in the gatewells.  Because of this anticipated stranding, several options for fish removal from gatewells were considered, including dip baskets, lift tanks, air-lift pumps, and screw pumps.  After analysis of these options, lift tanks emerged as the preferred choice.  Although similar to existing gatewell dip baskets, the lift tanks differ in several significant ways, such as size; frequency and duration of operation; and fish collection, transfer, and delivery.  Furthermore, unlike gatewell dip baskets, the proposed lift-tank system had not been evaluated.  At the request of the U.S. Army Corps of Engineers, we conducted a study to evaluate a prototype lift tank in 1994.  Results of that study are presented in this report.