Monitoring Plan Set for McNary Turbine Operations Changeby CBB Staff
Columbia Basin Bulletin - April 16, 2004
The Bonneville Power Administration, along with researchers at the U.S. Army Corps of Engineers, told the Technical Management Team this week that a monitoring plan has been prepared to track the impact on juvenile salmon and steelhead survival when operating turbines at McNary Dam outside the 1 percent peak efficiency range.
The NOAA Fisheries 2000 biological opinion of the Federal Columbia River Power System, in reasonable and prudent alternative (RPA) 58, calls for turbines to be operated within the 1 percent peak efficiency range during spring and summer while juvenile salmon migrants are in the river.
However, BPA said that operating outside the 1 percent range would reduce the amount of water that is involuntarily spilled at the dam during the spring runoff and that would provide an economic benefit to Bonneville, which could use the extra water to generate electricity. However, it also would put more flow through the turbines and decrease survival rates at the dam for yearling chinook and steelhead by a mean of 0.18 percent. That decline is because about 3.6 percent more juvenile fish will travel through turbines instead of over the dam's spillways.
"BPA's broad objective is to provide low cost power, while also meeting its fish and wildlife objectives," said Kim Fodrea of BPA. She said previous research at the dam indicates that operating outside the 1 percent limit doesn't significantly worsen survival, as previously thought.
If the water supply forecast at The Dalles Dam is 82 million acre feet, the annual revenue gain for BPA would be about $5 million for both spring and summer operations, Fodrea said. Spring operations would gain about one-half of that. In a normal water year, she said the spring and summer operations outside the 1 percent limit would gain BPA about $12 million. The actual April final water supply forecast at The Dalles Dam is 84.2 maf, or 78 percent of normal, January through July, a drop from 87 percent of normal in March.
She said BPA had pitched the proposal to TMT last year, but the idea was not well received. This year BPA is back with the same proposal, but has added an "extensive monitoring program," Fodrea said.
Rebecca Kalamasz of the Corps' Walla Walla District office said that if the operation causes problems with juveniles it likely would be most noticeable in the forebay and gatewell environments. That's why the plan focuses on monitoring fish injuries in those areas. That focused monitoring, she said, would allow for in season management decisions that could reinstate the 1 percent limit in order to minimize those impacts.
The operating limits were set as a result of studies in the early 1980s that led to the hypothesis that turbine efficiency and fish survival are directly related. However, BPA reevaluated those studies and, incorporating more recent studies at McNary Dam, now concludes that operating outside the 1 percent efficiency limit at McNary may not result in survival different than operating within the 1 percent limit, according to information provided by BPA.
At last week's TMT meeting, salmon managers, having heard about the new monitoring plan and BPA's coming proposal to operate outside the 1 percent efficiency range, submitted their own system operational request to ensure the BiOp operating limits are honored. BPA and the Corps asked salmon managers to wait and consider the monitoring plan, which they presented at this week's meeting.
With lower than average river flows predicted this year, BPA expects less involuntary spill. While Fodrea said TMT has time to decide whether to approve the change in operations and monitoring plan, Kalamasz said that a delay could impact the monitoring work that needs to get underway as soon as possible.
TMT will consider the operation again at its April 21 meeting.
Technical Management Team: www.nwd-wc.usace.army.mil/TMT/index.html
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