Albany Democrat-Herald
By Alex Paul
August 20, 2012

Juvenile steelhead and chinook salmon appear to have a greater chance of survival when passing over Foster Dam through a weir than through the turbine system, according to biologist David Griffith of the U.S. Army Corps of Engineers.

Although the final results of the first phase of a long-term study at the reservoir won’t be ready for a couple months, Griffith said early indications are encouraging.

“We tested fish weirs at both the 614 (above sea level) and 632 feet,” Griffith said. “And although mortality was higher at the upper elevation, it may still be lower than for those fish that passed through the turbines. The lowest mortality was through the lower weir.”

Griffith said similar research projects on the Columbia River saw survival rates of about 90 percent through turbines, but the Foster power plant turbine is smaller with a tighter geometry.

“The fish have a greater chance of getting hit at Foster,” Griffith said.

In May, biologists attached self-inflating balloons to smolt, then passed them either through the fish weirs attached to the spillway control doors or through the turbines.

When the balloons inflated, the fish would float to the surface and were gathered up by people waiting with nets. Their condition and/or mortality was noted.

Every 10th fish was actually an electronic monitoring device that allowed the researchers to study the forces exerted by the drop down the fish weirs or the turbines.

The units also recorded acceleration, spin and impact.

Griffith said the next phase of the multi-year project will be to study the seasonal run timing of fish past the dam.

“We will begin that phase this winter or early next spring,” Griffith said.

The final phase will be to attach radio tags to fish and “get really accurate information as to the distribution of fish through the routes.”

Griffith said the study will include how long the fish spend in the dam’s forebay.

The project is part of the Corps of Engineers efforts to comply with a July 2008 biological opinion issued by the National Marine Fisheries Service and the U.S. Fish and Wildlife Serice concerning the effects of dams on threatened and endangered species.

There are 13 Willamette Valley Project dams that were constructed between the 1940s and late 1960s. Those dams were designed for flood control, irrigation and recreation.

At Foster Dam, smolt currently pass through two turbines — and the bigger the fish, the more chance it has of being struck by one of the two spinning blades.

Since 2008, the Corps of Engineers has placed three metal units call “stop logs” into Spillway Bay 4 from mid-April to mid-May. The wall is topped with a notched segment called a weir, over which water passes at a controlled flow.

Corps of Engineers spokesman Scott Clemans said that the water near the reservoir’s surface, where young steelhead usually swim, spills through the weir’s notch at about 300 cubic feet per second.

The spilled water combines with that from the powerhouse to assist passage of the fish out of the South Santiam Basin and toward the Columbia River estuary and Pacific Ocean.

The public will be invited to learn about all of the mid-valley projects during several days of meetings in January 2013 in Corvallis.

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