Bonneville 'Corner Collector' Opens Today for
Changed conditions will allow an early opening after all of the "corner collector" at Bonneville Dam's second powerhouse to provide a safer passage route for spawned-out steelhead kelt and for any early migrating juvenile salmon and steelhead that approach the hydro project.
"We have come to a decision to open the corner collector on Friday morning, April 3," Dan Feil of the U.S. Army Corps of Engineers told the Technical Management Team Wednesday. The opening had been scheduled for April 10 when the dam's spill gates are opened to provide an additional passage route for young salmon and steelhead.
The fish can pass the dam through its hydro turbines, through mechanical bypass systems, through spill gates below the water's surface or through the surface oriented corner collector, a modification and extension of the powerhouse's existing trash and ice sluiceway.
The $50 million retrofit was completed in the spring of 2004 as a means of increasing fish passage efficiency at the dam. It delivers fish downstream in what the Corps believes is a more natural, benign manner.
The Oregon and Washington departments of fish and wildlife and the Nez Perce Tribe on May 11 submitted a system operations request to the TMT asking that the corner collector be opened immediately to facilitate any steelhead kelt working their way towards the Pacific Ocean.
The SOR said that, given "... the potential for improved juvenile survival of migrants passing during this no spill period and the Biological Opinion's reliance on kelt survival, it is appropriate to make a decision to operate the Bonneville Second Powerhouse corner collector beginning immediately...."
NOAA Fisheries' Federal Columbia River Power System BiOp judges whether federal Columbia and Snake river mainstem dams jeopardize the survival of salmon and steelhead listed under the Endangered Species Act. Snake River, Upper Columbia and Lower Columbia steelhead are among the listed stocks.
The TMT's federal, state and tribal fish and hydro system managers consider day-to-day operational strategies that are intended to benefit migrating salmon and steelhead.
The states and tribe said opening the surface passage route would help ease passage for weary steelhead kelt who had recently completed spawning upstream. They said the corner collector would get the steelhead past the dam more quickly and in better shape and thus improve their odds of surviving and returning to spawn again.
The federal "action" agencies – the Corps, the Bureau of Reclamation and the Bonneville Power Administration -- balked at the request for a variety of reasons. The 5,000 cubic feet per second flow through the corner collector would generate more total dissolved gas in the water below the dam and that increased TDG could put at risk newly hatched chum salmon. The Corps also said that no crane was available to pull the corner collector door open.
Federal officials said that providing depth compensation – -- raising the tailwater elevation by running more water through turbines – could help mitigate for the increased gas levels. But that would require additional drawing down of reservoirs upstream, such as Grand Coulee's. That could have put at risk refill goals at Grand Coulee. Stored water there is called on later in the season to augment flows for migrating salmon.
Bonneville officials also said they did not feel that the number of steelhead present at the dam in March warranted the expense of opening the door. That unleashed flow represents foregone power generating revenue – water that could have instead been channeled through the turbines.
The Corps and Bureau operate the federal dams; BPA markets power generated in the FCRPS.
Most of the concerns have gone away. A Corps crane that had been otherwise engaged is now freed up. And as of April 1 state waivers of TDG gas caps take effect. Instead of a 105 percent gas cap, the tailrace limit is now 120 percent. The waivers are requested so that spill, which also stirs up gas, can be provided for juvenile fish passage.
Additionally, emergence of young chum is now believed to be completed.
"We don't see much risk to chum," said Paul Wagner of NOAA Fisheries Service. Chum are also ESA listed. "We don't see TDG as much of a concern right now." That means there's no need to draw additional water from Grand Coulee.
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