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South Santiam’s Foster Dam Gets Improvements To Aid Juvenile Salmon Passage
Posted on Friday, December 01, 2017 (PST)

A winter upgrade to Foster Dam’s fish weir is expected to provide a safer passage over the dam for juvenile salmon and steelhead.


But first, the U.S. Army Corps of Engineers needs to remove a large crane from the dam’s upper deck that was once used for collection and passage over the dam of adult fish. That requires the Corps to close the road on top of the dam December 4 through 29, to all traffic in order to remove the crane.


Foster Dam is located on the South Santiam River, a tributary of the Willamette River, near Sweet Home, Oregon.


Once the crane is removed and out of the way, the Corps will install a newly-designed fish weir this winter, which the agency says should increase the cushion in the spillway for juvenile fish migrating downstream. The new weir will be taller than the existing weir and wouldn’t allow for Corps staff to place or remove it if the crane remained in place.


According to a Corps news release, a fish weir is a structure that is placed in a dam's spillway to manage water for juvenile fish passage. The weir constrains the release of water to maintain flow requirements, provides attraction for fish (stream-like flow from the surface of the reservoir) and creates a 'cushion' of water when landing on the spillway. This cushion makes the fall from the reservoir less harmful for the fish.


“The new weir is expected to effectively improve attraction, passage and survival of juvenile chinook salmon and steelhead,” said Jeffery Hicks, a Corps Portland District structural engineer. “It will do this, while minimizing impacts to other benefits of Foster Dam, such as flood risk management, hydropower generation and recreation.”


The Corps had been using the crane and elevator system, which it says was innovative for its time, for adult fish collection and passage over Foster Dam; however, the equipment wasn't fully successful in moving fish above the dam in an efficient manner. Corps biologists concluded there were better options.


"We found that transporting fish directly to the South Santiam allowed the fish to spawn more successfully," said Greg Taylor, Portland District fisheries biologist. "The crane became obsolete once we upgraded the fish facility."


Currently, the Corps partners with the Oregon Department of Fish and Wildlife to move fish above the dam after the fish climb a fish ladder to a collection facility, also known as 'trap and haul.' The crane is now in the way of Corps efforts to pass juvenile fish downstream of the dam, which is a requirement of the Willamette Valley Biological Opinion.


Photos are at:


The Corps announced a new facility at the dam in early 2015 that ensures fish can bypass the 126-foot flood control structure in better condition as they migrate upstream, improving the odds they reach their spawning grounds high in the South Santiam basin.


When Foster Dam was constructed in the 1960s, an adult fish collection system was included in the original design. The system included a ladder that guided fish into a holding pond and processing area adjacent to the spillway. From there, the fish were directed into a hopper basket, manually netted, placed into a truck, and transported upstream for release.


The new facility has several upgrades, including improved flows that attract salmon and steelhead to the base of the fish ladder more effectively, as well as larger holding pools that will minimize stressful overcrowding conditions.


Direct contact between fish and humans is significantly limited. Fish are sorted using a system that includes PIT tag detectors, hydraulic gates, and flumes (or chutes) that guide fish into holding pools or return them to the river. The fish collected in holding pools are transported to a truck using a new water-to-water transfer system that eliminates the need to dewater or capture fish in nets. The truck transports the fish upstream of the dam so they can spawn in the South Santiam River and its tributaries.


Also see:


--CBB, September 23, 2016, “Trucking Spawning Salmon Above Willamette Dam Showing Success In Offspring Survival, Adult Returns,”


--CBB, October 30, 2015, “Mortality For Transported Willamette Spring Chinook Declines When Held In Cool, Pathogen Free Water,”


--CBB, February 6, 2015, “Upgrades At Oregon’s Foster Dam (South Santiam) Fish Passage Facility Aimed At ESA-Listed Salmonids,”


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