Juvenile Bypass System

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The Wells Project’s juvenile bypass system was completed in 1989. The bypass system was developed to guide downstream migrating juvenile steelhead and salmon away from the turbines and into the spillways. The bypass has an efficiency rate of 92.0% for spring migrants and 96.2% for summer migrants (Skalski et al., 1996) and is the most efficient bypass system on the mainstem Columbia River. The system was developed by modifying the upper portions of spillways 2, 4, 6, 8, and 10. Each spillway has three sections. The bypass system modifies the two outside spill sections with solid steel barriers and the middle section with a slotted steel barrier. The slotted barrier has an opening that is 16 feet wide and 72 feet deep. During bypass operations, the gates on spillways 2, 4, 6, 8, and 10 are opened approximately one foot when an adjacent generating unit is operating. Spillways 2 and 10 are also configured to allow passage through either the ice trash sluiceways or through the bottom spill gates. Since most juvenile salmon and steelhead migrate near the surface, with the help of the bypass system they successfully pass Wells Dam and avoid the turbine intakes located below the bypass entrance. The bypass system is in operation annually from mid-April until late August. Because all 11 spillways may be needed during emergency operations, the bypass barriers are designed to collapse when the spillway gates are opened more than six feet.

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