PORTLAND — A federal judge says the government’s latest plans for making Columbia Basin dams safer for salmon look good, but a legal flaw could delay his approval.

Judge James Redden said Monday that approving the plans as they stand could make his decision vulnerable on appeal for violating federal procedural rules.

But Redden noted that sending the plans back to the government to do over could add months or more to litigation that has gone on for 15 years.

Redden made clear Monday at a hearing he called the most important in the case that he favored the administration’s plans, which are opposed by environmentalists, the state of Oregon and the Nez Perce tribe.

He has rejected two previous plans, known as biological opinions or “biops.”

“I really think that with a little more work, we have a biop,” he told the lawyers representing the federal and state governments, environmentalists, Indian tribes, salmon fishermen, sporting equipment dealers and others.

The federal government is supported by several Northwest tribes and the state of Washington.

The suit has wide-ranging consequences in the Pacific Northwest because it balances cheap electricity from hydropower dams against the fate of species of salmon and steelhead protected by the Endangered Species Act and prized by fishermen. The dams kill fish, and changing the way they’re run to help the fish cuts electrical output.

The basic plan Redden is considering was drawn up last year by the Bush administration.

This fall the Obama administration offered additional proposals that included fallback measures if fish numbers crash and consideration of breaching dams on the lower Snake River in Washington state.

Redden said the two efforts combined “are really a good piece of work.”

But in a letter to lawyers in the case this month, Redden said the rules forbid him to consider some material that comes in after an agency decision such as the 2008 plan has been made, and the Obama administration would have to make public some of the documents it considered in drawing up its proposals.

“It’s not a technicality,” Redden said Monday. “It’s important.”

He did not resolve the issue. He asked the lawyers for written briefs next month.

Redden also raised the possibility of the plans setting aside more water for fish without taking down dams.

The importance of the hearing was highlighted by the presence of Jane Lubchenco, a marine ecologist at Oregon State University before she was appointed administrator of NOAA, the federal agency that oversees marine fisheries.

After the hearing, Lubchenco said the agency was eager to begin putting fish protection plans to work and expects soon to release documents used in its proposals. “We have no problem sharing that science,” she said.