The benefits of creating a fresh-water lagoon in the Russian River at Jenner for the survival of juvenile steelhead outweigh the negatives, such as the possibility of worsening water quality, Sonoma County officials decided Tuesday.

The Board of Supervisors, which faced a violation of the federal Endangered Species Act if it did not take action, approved the final environmental report on the Sonoma County Water Agency's project.

"The urgency is high that we do this today," even though the board would have preferred the discretion to do more research, Supervisor Shirlee Zane said. "But the benefits outweigh the effects of this project."

The water agency has been ordered by the National Marine Fisheries Service to manage the Russian River at Jenner to create a fresh-water lagoon during the summer to allow juvenile steelhead, a threatened species, to acclimate before going out to sea.

To meet the order, the water agency has developed a method to let the water back up behind the sand bar when the river mouth is closed.

Instead of digging a ditch to the ocean to let the river out, the water agency lets the water rise to a depth that is just below flooding low-lying buildings in Jenner and then digs a broad, shallow northwesterly outlet to the sea.

That creates is a lagoon that is more fresh water than salt water for a longer period of time for the steelhead.

Studies on similar California estuaries, such as Carmel River, Scott Creek and the Pescadero Marsh, indicate there are substantial benefits of a fresh-water lagoon for steelhead, according to federal biologists.

The federal agency also has ordered the water agency to lower flows in the Russian River to protect chinook, which are also threatened, and to create habitat in Dry Creek for coho salmon, which are endangered.

"It is a moral imperative," said Dick Butler, a regional supervisor for the National Marine Fisheries Service. "If we continue with the status quo, we will endanger the steelhead, coho and chinook salmon."

The orders were issued in 2008 and the agency was required to begin the program at Jenner immediately. Since then, it has had to manually breach the sandbar only once, in July 2010, when river flows were not sufficient to naturally open the sand bar.

The estuary program costs $950,000 a year, mostly for the expense of studies on water quality and fish along the river from Jenner to Monte Rio.

The impact report, which cost $850,000, indicated that there are possibilities of some decrease in water quality in the lagoon as more river water is allowed to stagnate there.

With higher water in the lagoon, <NO1><NO>a tsunami could worsen flood danger, seals and sea lions could be impacted and sand could be swept south on the coast and worsen conditions for surfers as some beaches.

Russian River residents contend that the project will seriously worsen water quality, that heavy equipment will chase away the seals and sea lions that gather <NO1><NO>on the sand bar and the impacts should be studied in conjunction with the other federal orders.

"To say that there is not significant problems with lower flow on water quality is simply not true," said Brenda Adelman of the Russian River Watershed Protection Committee. "Everybody who lives on the river has seen it and lives with it."

Mary Anne Sobieraj of Cazadero questioned whether the studies in other watersheds apply to the Russian River.

"None of the watersheds that you studied are like the Russian River," Sobieraj said. "They don't have the urban influence and all are less than 10 miles long."

Norma Jellison of Jenner said she had no confidence the project would be successful.

"There is no concern for the moral imperative for any other species, the impacts to public access, to the people who come from all over the Bay Area, the state and the world to stand on the overlook," Jellison said.

However, Butler warned that if the board did not certify the final environmental impact report, theSonoma County Water Agency would be out of compliance with the Endangered Species Act and subject to a federal action.

Supervisors certified the report in a 5-0 vote.

"What we are trying to do is the right thing, to protect the fisheries," said Supervisor David Rabbitt.