Lower Granite Juvenile Fish Facility Phase 1a

  • Lower Granite Juvenile Fish Facility Phase 1a
  • Lower Granite Juvenile Fish Facility Phase 1a
  • Lower Granite Juvenile Fish Facility Phase 1a
  • Lower Granite Juvenile Fish Facility Phase 1a

Lower Granite Juvenile Fish Facility Phase 1a

Lower Granite Dam
Customer: Walla Walla District, US Army Corps of Engineers
Date Completed:

Garco has been working since January 2015 on the $50 million Lower Granite Juvenile Fish Facility Phase 1a contract for the Walla Walla District, US Army Corps of Engineers.  The project constructs a new downstream juvenile fish bypass facility to improve the survival rate of salmon and steelhead smolts crossing Lower Granite Dam on their journey from the spawning grounds to the ocean.  New features include over 2500 feet of elevated structural steel flume, carried by a combination of structural steel trusses, plate girders, and steel piping, and supported on 52 steel or concrete columns atop drilled shafts up to 8 feet in diameter.  The flume incorporates a 3-level spiral loop structure to maintain no more than a 4% slope while decreasing 70 feet in elevation.  Two dewatering structures concentrate the fish prior to entering the Juvenile Fish Facility (JFF) for loading into barges or discharge to the river.  The new bypass will reduce fish mortality by providing a much more gradual descent than the existing pressurized pipe system.