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Removable Spillway Decision at Ice Harbor Goes to Fed Execs

by Mike O'Bryant
Columbia Basin Bulletin - December 5, 2003

NOAA Fisheries is leaning towards recommending to the Federal Executives that they approve at their Dec. 17 meeting the installation of a removable spillway weir at Ice Harbor Dam, to be completed before the spring juvenile salmon migration begins in 2005.

The topic has dominated discussion at System Configuration Team meetings for over two months, but SCT biologists have yet to reach a consensus among three options being considered, said Bill Hevlin of NOAA Fisheries and SCT chair. Hevlin elevated the discussion, but not the decision, to the Implementation Team at its monthly meeting this week.

The U.S. Army Corps of Engineers installed an RSW at Lower Granite Dam in early 2002 to improve fish passage and survival at the dam. Early results showed that both passage and survival improved and that it was accomplished with less spill at the dam. Seeking a lower cost and more effective way to spill water to improve fish survival, the Bonneville Power Administration in October 2002 proposed to SCT to accelerate the installation of RSWs at Ice Harbor and Lower Monumental dams and to install the devices as soon as possible.

"SCT's response was that it is interesting, but we would need more data to decide about Ice Harbor," Hevlin said at the IT meeting.

SCT told BPA in January 2003 that a decision could not be made without further studies at Ice Harbor Dam to determine what is influencing the lower than expected survival at the dam and after another year studying Lower Granite Dam's RSW, Hevlin said.

"Now we have the decision whether we should commit '04 funds and have the RSW at Ice Harbor ready for the spring migration," Hevlin said. "We're looking for regional input, but ultimately it will be the Executives' decision."

Preliminary results of an evaluation of the RSW at Lower Granite Dam show that survival probability rises from 93.1 percent with spill to 98 percent with the RSW and that survival is more consistent over the entire spill season with the RSW. Spill provides less consistent survival over the season, said Noah Adams of the U.S. Geologic Survey.

Given that success, the Corps, BPA and NOAA Fisheries have concluded that an RSW would also benefit passage at Ice Harbor Dam, while providing BPA a financial advantage (less spill). BPA had estimated that savings from using the RSW at Ice Harbor Dam could be as high as $22 million a year due to reduced spill levels. ("This calculation was based on a 50 year average spill level at 19 kcfs," according to notes from SCT's Nov. 21 meeting. Spill at 35,000 cubic feet per second is also being considered.) Design work on an RSW for Ice Harbor Dam is already underway.

However, SCT participants are not in total agreement with findings at Lower Granite Dam, and some wonder if survival could be improved at Ice Harbor Dam through other means.

When spilling, survival at Ice Harbor Dam is lower when the river flow is lower, said Brad Eppard of NOAA Fisheries in Pasco, Wash. Spill below a flow level of 90 kcfs "may create a hydraulic condition that is bad for fish," he said.

Tests this year at the dam of different spill gate openings and of going to bulk spill increased survival through spill to 96.4 percent, according to a chart provided by Eppard. While the NOAA Fisheries 2000 biological opinion calls for 98 percent passage survival at the dam, only in 2000 did survival come close when yearling chinook passage was measured at 97.8 percent. That dropped to 89.2 percent in 2002, and in 2003, survival was 94.8 percent with BiOp spill and 92.8 percent at 50 percent spill. Subyearling chinook fair worse: 2000 survival was 88.5 percent, while 2002 survival was 89.4 percent.

"We've been getting inconsistent results with spill at Ice Harbor, so it's very important that we identify how to improve survival through spilling at Ice Harbor," Hevlin said.

SCT has been considering three alternatives for RSW construction:

  1. Currently, the Corps is on a fast track plan to install an RSW at Ice Harbor in 2005 and to follow that in 2006 by installing an RSW at Lower Monumental Dam. An RSW at Little Goose would follow in 2007. The Corps is on track to install the Ice Harbor RSW if the region reaches a final decision on the project by January 2004. It has yet to start modeling for the Lower Monumental installation, but will begin in January or February 2004.

  2. NOAA Fisheries favors the second option, which calls for installation of an RSW at Ice Harbor Dam in 2005, with continued studies at Lower Granite Dam and phasing in lower spill at Ice Harbor Dam after the RSW is installed. The NOAA plan also includes installation of RSWs at Lower Monumental in 2006 and at Little Goose in 2007.

  3. Install an RSW at Little Goose in 2006. In the mean time, finish spillway survival studies at Ice Harbor Dam to determine why survival rates are lower than expected. Lower Monumental RSW construction would follow in 2007 and Ice Harbor in 2008, if studies determine it is needed.

The second plan is endorsed by NOAA Fisheries and Idaho Fish and Game, while salmon managers favor the third option. Howard Schaller, U.S. Fish and Wildlife Service, asked if the region is satisfied enough with the results of studies for the Lower Granite Dam RSW to move ahead.

"Are we satisfied that these results are so dramatic that we want to install them everyplace?" Schaller asked. He said 2002 and 2003 flows were similar and suggested further study that would look at the RSW performance over a wider range of flows.

Bill Tweit, Washington Department of Fish and Wildlife, wondered what "would get bounced out of the SCT budgeting process" if going forward on the accelerated construction plan. "What are we loosing that really needs to be done to do this in 2005?" he asked.

Hevlin said the Corps has already set aside $3 million for 2004, so the accelerated schedule would not displace other projects.

In addition, Tweit was uncomfortable extrapolating results at Lower Granite to Ice Harbor Dam when, according to Tweit, design of Lower Monumental and Little Goose dams were more like Lower Granite Dam than is Ice Harbor Dam.

"I'm more comfortable trying an RSW at a facility more like Lower Granite," he said. "It's more of a jump of blind faith to go all the way down to Ice Harbor first. It's the greatest possible leap we could make with the limited amount of data we have."

"The design at Ice Harbor is nearly identical to Lower Granite due to similarities in profile and hydraulics," said Steve Rainey of NOAA Fisheries. "We expect similar survival at Ice Harbor."

"We're uncomfortable that the RSW gives similar survival benefits as bulk spill," said Tom Lorr of the Columbia River Inter-Tribal Fish Commission. "I don't think we have a solid hypothesis yet about the problem with the spillway (at Ice Harbor). It's premature until we solve some of these uncertainties." He added that the tribes would write comments to the Federal Executives in the next couple of weeks.

"We didn't have a clean idea of what would happen with the RSW at Lower Granite," said Jim Litchfield, representing Montana. "So, that didn't meet your standard, either."

"We believe that within several years all these problems will be resolved," Rainey said.

Hevlin said that Ron Boyce, Oregon Department of Fish and Wildlife, who could not attend the IT meeting, was concerned that performance objectives had not yet been established for RSWs. Those objectives should address project survival, spill passage efficiency and residence time, among other issues.

Facilitator Donna Silverberg suggested that SCT or IT focus on establishing those standards in December and January.

Related Sites:
Implementation Team:

Mike O'Bryant
Removable Spillway Decision at Ice Harbor Goes to Fed Execs
Columbia Basin Bulletin, December 5, 2003

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