ROGUE RIVER — State fish biologists and the federal Bureau of Reclamation are at odds over whether concerns about Rogue River's chinook salmon should delay the planned April start of Savage Rapids Dam's demolition.

ROGUE RIVER — State fish biologists and the federal Bureau of Reclamation are at odds over whether concerns about Rogue River's chinook salmon should delay the planned April start of Savage Rapids Dam's demolition.

Oregon Department of Fish and Wildlife biologists fear plans for removing the north side of the 88-year-old dam risk rendering the dam's only remaining fish ladder as impassable at times to the Rogue's depressed run of wild spring chinook.

Based on bureau computer modeling of water through the ladder, the ODFW insists the ladder should be modified to slow down flows to chinook-friendly levels before April 7. That's when work is planned to begin on a coffer dam that will force water away from the existing dam so demolition can begin.

If not, the state agency wants the bureau to halt construction of the coffer dam until August, when all the spring chinook have passed the structure and lower and slower water flows pose less of a risk, according to the ODFW.

ODFW biologists say they will withhold a state fish-passage permit for the April work unless the modifications are made and a detailed plan is written about how the bureau would deal with any fish-passage crises there.

"There appears to be a new level of risk that wasn't anticipated earlier and we don't think it's had an adequate response," said Dan VanDyke, the ODFW's Rogue District fish biologist. "The risk to passage is high in the spring and lower in late summer and fall."

Bob Hamilton, the bureau's project manager, said pushing the bulk of the in-stream work to late summer and fall would affect the fall run of wild coho salmon.

Since coho are listed as threatened under the federal Endangered Species Act, they demand top priority for protection by the bureau, Hamilton said.

"Frankly, if we're going to stress a run it has to be the chinook, not the coho," Hamilton said. "We believe we have to have this April option to protect the coho.

"Coho, in essence, are paying the bills for this work," Hamilton said. "That's the federal nexus."

Hamilton said the bureau has agreed to some changes to slow flows through the ladder this spring, but the agency has no intention of delaying the project for improvements to the ladder, Hamilton said.

"This is a dam-removal project, not a fish-ladder renovation project," Hamilton said.

State Department of State Lands and the U.S. Army Corps of Engineers permits — created in consultation with the ODFW and federal NOAA-Fisheries in 2006 — cover the new modifications and allow the project to move forward, Hamilton said.

"Why should we be applying for a permit for a plan we developed with the ODFW and NOAA-Fisheries?" Hamilton said.

The bureau intends to have contractors move forward as scheduled, removing the dam by year's end, Hamilton said.

"Shifting the start date to August makes it a tight window to get all the work done this calendar year," Hamilton said. "That does away with the flexibility we have and puts the pressure on coho."

VanDyke said the ODFW will have "added discussions" to figure out how best remove the Rogue's single largest fish-killer without harming this year's runs in the process.

"Everybody wants this project to succeed," VanDyke said.

Fish-passage headaches are nothing new at Savage Rapids Dam, which will be replaced by new electric pumps this spring to provide water to Grants Pass Irrigation District customers.

It sports two fish ladders, but the north ladder would not receive water once work begins to remove the dam's northern panels and let the Rogue flow freely through it.

That leaves the south ladder, which was originally built in 1935 and modified several times to improve its efficiency.

At issue is whether the Rogue's spring flows through the ladder will remain slow enough that adult spring chinook can negotiate the series of jump pools to cross over the dam.

In a 2006 federal biological opinion required for the bureau to get its removal permit, biologists said the Rogue could flow at up to 6,000 cubic feet per second before flows in the ladder would become a migration barrier.

At the request of the ODFW and NOAA-Fisheries, the bureau last fall created a three-dimensional computer model of the ladder. That model concluded that flows in the ladder would create a barrier at just 1,100 cfs. — well above regular flows expected in spring.

"We want the dam out of there this year," said Russ Stauff, the ODFW's Rogue Watershed manager. "But if they insist they don't need a permit and they're moving forward in April, and if there's a problem with spring chinook, then they are accountable for it."

Hamilton said the bureau plans to open the radial gates and the dam's base to divert more flow away from the ladder. The bureau plans to have contractors build a sandbag buffer to help herd migrating spring chinook toward the ladder and away from the outflow from the radial gates, he said.

With these changes, Hamilton said the ladder should remain operable at river flows up to 10,000 cfs.

"The modeling points out that the ladder is a poorer fish-passage mechanism than anyone thought," Hamilton said. "The only way you can really fix it is to blow it up and start over," Hamilton said.

"We believe we're providing the best solution," he said. "We're all trying to get to the same place. We just disagree a little on how to get there."The whole debate becomes moot if rain and snowmelt swells the Rogue in early April.

Hamilton said plans are not to install the first coffer dam beginning April 7 if flows exceed 4,000 cfs — too high to put the temporary dam in place.

"Mother Nature," Hamilton says, "may resolve the entire discussion."

Reach reporter Mark Freeman at 776-4470, or e-mail mfreeman@mailtribune.com.