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Staff Accomplishments

New test bed to provide information for fish-friendly culverts

April 2004
Thousands of miles of essential juvenile salmon habitat are blocked by tens of thousands of culverts that lay beneath Pacific Northwest roadways. Many of these culverts, which for years have successfully channeled water under roadbeds, are acting as barriers to young salmon, preventing them the upstream passage required for growth and development. Researchers from the Environmental Technology Directorate at the Pacific Northwest National Laboratory (PNNL) have designed and installed a culvert test bed in southeastern Washington to help the Washington State Department of Transportation (WSDOT), and several West Coast transportation agencies find a more "fish friendly" design for future stream crossings and for the thousands of retrofits expected to be completed in coming years. "We're blending the expertise of hydraulics engineers, mechanical engineers, statisticians, fish biologists and fish behavior specialists to find a solution to a problem that faces the entire Northwest, and has implications for culverts throughout the country," said Walter Pearson, PNNL fish behaviorist and program manager. The full-scale, one-of-a-kind culvert test bed is located at the Washington Department of Fish and Wildlife Skookumchuck Hatchery near Tenino, Wash. The system allows scientists to adjust and measure the hydraulic conditions, such as water velocity, turbulence and depth, of various culvert designs being evaluated. By assessing different slopes and flow regimes, scientists can determine how these conditions influence fish behavior and the ability of the fish to pass through a variety of culvert designs being considered as retrofits. "There are hundreds of possible test bed configurations," Pearson said. "A particular design may stop passing fish at some flow rate or some slope and that's what we'll be looking for. This will help us design stream crossings that accommodate fish in all life stages." The ability to quickly receive research results on these configurations is very appealing to transportation agencies. "Testing culvert designs in a controlled setting will help us better understand how we can meet fish passage needs in a variety of conditions," said Paul Wagner, from WSDOT's Environmental Affairs Office. In coming years, tens of millions of dollars will be spent improving culvert fish passageways in Washington State alone. Attempts to retrofit culverts are not new. Baffles, weirs, ladders and other physical structures have been added to enhance fish passage over the years, but there is insufficient data to demonstrate the effectiveness of these efforts. The culvert test bed will provide decision-makers scientifically sound data to retrofit existing culverts and develop better designs for new culvert installations. "Investing in this system provides WSDOT with improved scientific data to ensure that we're spending money on solutions for fish passage that will work to provide long-term benefits to our environment," said Wagner. A transportation consortium that includes the states of California, Oregon, Washington and Alaska, and the Federal Highway Administration pooled funds totaling $1.16 million to contract with PNNL to conduct the first phase of a five-year $3.4 million interdisciplinary program. Other participants in the project include the Washington Department of Fish and Wildlife and Alaska Fish and Game. Scientists with extensive natural resources and hydraulics expertise were selected from PNNL's Marine Sciences Laboratory and its Hydrology Group, to design, install and operate the culvert test bed. PNNL recently completed installation of the test bed, has tested the mechanics of the device, and is currently performing hydraulic characterization. Passage of juvenile salmon through culverts is a significant Endangered Species Act issue for Pacific states. Scientists recognize fish passage both up and downstream is crucial for the rearing and feeding of young salmon. The test bed enables controlled experiments that will yield the behavioral and hydraulics data to address this ESA issue. Funding for the test bed project was provided WSDOT through an 1830-related services contract.

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