Removable Spillway Weir (RSW), Lower Granite Dam

The purpose of the RSW is to pass juvenile salmon and steelhead downstream over a "raised" spillway crest, similar to a waterfall. Existing spillways use gates that are open 50 feet below the water surface. This forces the young fish to pass through the spillway under these gates at high pressure and velocity. The prototype weir will allow the gates to be fully raised so that the fish can pass through the spillway near the water’s surface at much lower pressure and velocity. This new passage system will be a more efficient and less stressful passage route for the juvenile fish.  The weir will be fitted into spillway #1 at Lower Granite. The structure is designed so that in the event of a major flood the RSW can be lowered out of the way into the forebay thereby opening up the spillway to full flow capacity. The weir would then be raised to operating position after the flood event. The RSW weighs over 1.8 million pounds, is 115 feet tall, 83 feet wide, and 61 feet deep in the upstream to downstream dimension.

Lund Engineering worked directly for Jacobs Sverdrup and was responsible for the design and engineering of the RSW’s pier connections, main pivots and air servo-control system.

Click here for a movie of the RSW launch.

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