Sean C. Morgan
Foster Dam Road will be closed for most of the month of December while the U.S. Army Corps of Engineers removes an unused crane to make room for a new weir structure that will help juvenile fish move downstream over the dam.
The Corps plans to close the road Monday, Dec. 4, through Dec. 29. During that time, the road will be closed to all vehicle and pedestrian traffic.
For a time, the Corps used the crane and elevator system, which 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 Corps completed construction of a brand new fish collection facility in 2014.
“The crane became obsolete once we upgraded the fish facility,” Taylor said.
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, which was built and completed with the dam in 1968, 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, said Corps Spokesman Tom Conning.
The Corps has been using a “fish weir” to allow fish to pass over a spillway at Foster Dam and are upgrading that weir.
A fish weir is a structure that the Corps places 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 taller and it won’t allow Corps staff to place or remove it if the crane remains in place.
The new weir is expected to effectively improve attraction, passage and survival of juvenile Chinook salmon and steelhead, said Jeffery Hicks, 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 will install a newly designed fish weir at Foster later this winter, which should increase the cushion for fish migrating downstream.
Foster Dam generates power and regulates flows from the Green Peter Dam upstream on the Middle Fork of the Santiam River.