A panel of scientists is developing a plan to carry out spill operations at Libby Dam to benefit the endangered white sturgeon, but there is a major legal obstacle that could plug up the dam's spillways for years to come.

An effort is under way to implement a recently released federal biological opinion aimed at saving white sturgeon in the Kootenai River.

Participating are technical and biological experts from the U.S. Army Corps of Engineers, the Bonneville Power Administration, the U.S. Fish and Wildlife Service, the Kootenai Tribe of Idaho, the Confederated Salish and Kootenai Tribes and the states of Montana and Idaho.

The centerpiece of the biological opinion is a call for the Corps to provide flows that exceed the 25,000 cubic feet-per-second powerhouse capacity at Libby Dam by 10,000 cfs at least three times over the next 10 years.

"The intent is to mimic as closely as possible the timing, temperature and shape the river flows would have had before Libby Dam was built," a Corps press release states.

The problem with exceeding powerhouse capacity is there is only one way to do it - releasing water over the dam's spillways. And doing that to the extent the biological opinion calls for would violate Montana water-quality standards.

"It's a huge obstacle," said Brian Marotz, special fisheries projects manager for Montana Fish, Wildlife and Parks.

Marotz, who is deeply involved with the sturgeon conservation effort, explained that Montana effectively adopted the federal Clean Water Act in its entirety. And there is no way for state officials to allow for deviations from the act's standards on dissolved gases in state waterways.

Spills in the range of 1,000 cfs to 2,000 cfs at Libby Dam will "cross the line" and exceed the state's gas saturation standards.

"We don't have a mechanism for a variance around that standard," Marotz said. "The only way to get around [the standard] would take a legislative action to change it."

The standard is written specifically to prevent harm to fisheries and aquatic insects, Marotz said, and there is a track record showing how spilling water at Libby Dam can cause harm.

An experimental spill that became an uncontrolled spill (due to heavy runoff in spring 2002) produced a high incidence of "gas bubble trauma" in fish below the dam. With more than 16,000 cfs going over the dam's spillways at one point, gas levels in the river became dangerously high.

Fish developed bubbles in their eyes, along their lateral lines and in their gill filaments. But Marotz and other state officials who monitored the situation never found any mass fish mortality.

Judging from that incident, Marotz said it is believed a spill of 10,000 cfs could be carried out for up to seven days without causing gas bubble trauma.

"We probably wouldn't see a high incidence of gas bubble trauma, unless it went on longer than that, and then it would happen very rapidly," he said.

But still, those flows would exceed state water-quality standards.

There may be more realistic ways to improve conditions for sturgeon, Marotz said.

Mechanically deepening the river channel in certain places is being considered as a way to improve spawning conditions.

The biological opinion is largely focused on providing water depth and velocity for sturgeon spawning in a stretch of river upstream from Bonners Ferry, Idaho. The "Braided Reach," as it is known, is thought to have the proper cobble-and-gravel riverbed that would allow for successful wild sturgeon spawning.

"But providing additional flow from Libby Dam is the only tool currently available to assess the effects of additional depth on sturgeon spawning and migration," this week's Corps press release states. "And it's the only tool that will allow a complete assessment of sturgeon response to these depths while enough adult fish remain in the river to spawn."

But Marotz is not optimistic that Montana state officials will have the legal ability, much less the willingness, to go along with the federal biological opinion.

"All indications are that Montana isn't at all interested in doing this," Marotz said.

It's currently estimated there are only 500 wild adult sturgeon remaining in the Kootenai River. That would put the population on the brink of extinction if not for a successful hatchery program, run by the Kootenai Tribe of Idaho, that puts juvenile sturgeon into the river.

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com