July 29, 2004

Salmon get a boost from technology

  • Army Corps is building a giant antenna to detect tagged fish as they use a new bypass channel at the Bonneville Dam.
    U.S. Army Corps of Engineers

     Columbia River
    Photo courtesy U.S. Army Corps of Engineers
    Water spills into the Columbia River after it navigates the ogee section of the corner collector channel.

    On April 11, fish christened the Bonneville second powerhouse corner collector — a new surface flow bypass channel — as they made their way downstream in the Columbia River.

    The idea for the new facility, completed in December 2003, was conceived in 1998 when field testing by U.S. Army Corps of Engineers biologists revealed that about 40 percent of juvenile fish in the area directly upstream of the second powerhouse were passing the dam through the existing ice and trash sluiceway — a chute used to funnel debris around the dam.

    Though the fish were drawn to the sluiceway — and 99 percent of them safely exited it — improvements to the channel's structural and biological hydraulics were made to create a more fish-friendly environment. The improvements included rerouting the exit, or plunge pool, further downstream in faster moving water, away from predators. That also prevented water from slamming fish at the bottom of the chute, said corps fishery biologist Dennis Schwartz.

    The project team
    U.S. Army Corps of Engineers

    U.S. Army Corps of Engineers

    General contractor:

    Entrance gate design:
    INCA Engineers

    Physical hydraulic modeling:
    U.S. Army Corps of Engineers

    Numerical hydraulic modeling (outfall):

    Numerical hydraulic modeling (entrance):
    Pacific Northwest National Laboratory

    Geotechnical data:
    Cornforth Consultants

    Oregon, Idaho and Washington fisheries agencies, NOAA Fisheries, tribal agencies, the Bonneville Power Administration, and the corps endorsed the $48 million project as a viable means to increase juvenile fish survival.

    The 2,800-foot-long bypass flume begins at the upstream southeastern corner of the powerhouse, where a moveable gate can be raised to allow about 5,000 cubic feet per second of water to spill into the modified ice and trash chute and then on through the 500-foot-long outfall channel that transports fish around the powerhouse. The fish will re-enter the river into the plunge pool just beyond the westernmost tip of Cascades Island, about a half-mile downstream.

    The corps estimates that about 50 percent to 60 percent of juvenile fish entering the forebay now will be guided into the corner collector. Considering that the project also will work in conjunction with Bonneville Dam's existing second powerhouse screened juvenile bypass system, the two non-turbine routes will pass about 90 percent of all juvenile fish in the second powerhouse forebay, with an estimated survival rate greater than 98 percent, Schwartz said.

    Fish behavior

    The corps hopes to confirm successful passage through the corner collector — and learn more about fish behavior just outside the entrance to the facility — when results are in from two studies.

    In one study, biologists release radio-tagged fish above Bonneville Dam and follow their routes of passage, whether they reach the downstream side of the dam via the corner collector, the spillway, turbines or the bypass facility.

    In another study, underwater cameras capture fish behavior just outside the entrance to the corner collector to help biologists determine if entrainment flow attracts the fish, discourages the fish or has no impact at all.

    Results of the studies will be available for the biologists to review in this fall.

    While biologists perform the studies to help them know more about fish behavior, they also fulfill regional information requirements. NOAA Fisheries, the federal agency responsible for managing salmon and steelhead listed as threatened under the Endangered Species Act, has required the corps to provide survival information for fish migrating through the Columbia and Snake River System.

    PIT tags

     PIT tags
    Photo courtesy Pacific States Marine Fisheries Commission
    PIT tags the size of a grain of rice are loaded into hypodermic needles, and then injected into sedated fish.

    "Many of the corps- and BPA-sponsored juvenile salmonid survival studies use PIT (passive integrated transponder) tags," said Kim Fodrea, BPA's fish and wildlife project manager.

    A PIT tag is an electronic device about the size of a grain of rice that is inserted via a hypodermic needle into the body cavity of a sedated juvenile fish. When detected by an antenna, the tag acts much like a barcode, providing a unique identification to each individual fish from which biologists can obtain information such as the fish's species, journey origin and age. The fish are then returned to the river.

    The corps has antennas at most of its juvenile bypass facilities and many of its adult fish ladders to detect returning adults. Most of the antennas are designed to fit around 1-foot to 3-foot cylindrical pipes with only a half-cubic-foot per second of water running through them. The corner collector, however, does not have a PIT tag antenna, meaning the 50 percent to 60 percent of fish using the collector will go undetected.

    Photo courtesy U.S. Army Corps of Engineers
    The 40-foot-wide, 500-foot-long concrete monolithic outfall structure was built with the help of a crane mounted on a barge.

    The System Configuration Team, a regional fish management group made up of representatives from state, federal, and tribal interests on the Columbia River that advises the corps on priorities for fish passage actions for the hydropower projects, wants a PIT tag antenna added to the corner collector and has made the work a regional priority. State, federal and tribal fish and wildlife managers also have prioritized the project for funding by BPA under the Northwest Power and Conservation Council's fish and wildlife program.

    Antenna construction

    The corps and BPA are working to design, construct, operate and maintain a newer and much larger PIT system at the Bonneville corner collector that will work in high flow situations, Schwartz said. An agreement between the two agencies provides that BPA will fund the electronics for all PIT tag detection projects and the corps will fund the structural/infrastructure changes and additions for these projects.

    Photo courtesy U.S. Army Corps of Engineers
    Corps workers install temporary hydraulic instrumentation into the completed corner collector channel.

    Both agencies are working with Digital Angel to design a PIT tag system to meet a detection goal of 60 percent, a goal recommended by the Regional Research, Monitoring and Evaluation workgroup.

    "Through improvements in the antenna and reader designs, as well as the continuing tag enhancements, Digital Angel expects to get 60 percent or better by the conclusion of the development," said Sean Casey, Digital Angel's fisheries project manager tasked with antenna electronics development.

    The prototype antenna at the corner collector will be 16 feet by 16 feet, Schwartz said, dwarfing other systems of this type. "The less invasive you can be, the better. It will be much easier on a fish to be diverted into a 16-foot-wide channel than into a 12-inch pipe," he said.

    In early February 2004, the corps awarded a contract to Accord Construction to begin the work on a watertight pool near Bonneville Dam to test the new PIT tag antenna prototype. Northern Marine, a subcontractor to Accord, was given the task of making the antenna, which is being tested this month by the corps and BPA.

    watertight pool
    Photo courtesy Digital Angel
    An Accord Construction worker enters the watertight pool that will be used to test the prototype PIT tag antenna.

    If successful, Schwartz said the antenna used for the prototype testing would be permanently installed in the channel in the upcoming fall/winter. Using the prototype is expected to save thousands of dollars by not duplicating equipment.

    Schwartz said they are looking at potentially needing an extreme makeover for the PIT tag itself in the long-term. This plan, however, is contingent on production testing of newly developed PIT tag materials in the spring of 2005. Results of this test will determine the final design that will be available for use in the 2006 to 2008 fish passage season, depending on the processes/materials needed to meet or exceed the detection goals, Schwartz said.

    In the mean time, fish will be traveling down the water freeway that promises them a speedier route past the dam as well as higher survival to the Columbia River estuary.

    Heidi Helwig is a public affairs specialist with the U.S. Army Corps of Engineers, Portland District.

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