SACRAMENTO — A last-minute intervention by the Federal Aviation Administration halted the approval of a proposed Hayward power plant today.

Twenty-five minutes before the California Energy Commission was poised to vote on the 600-megawatt Russell City Energy Center, a safety manager for the FAA e-mailed the commission requesting time to research how the plant might affect aviation safety.

Pilots are worried that intermittent hot plumes of exhaust could rise quickly from the natural-gas-fired plant's cooling tower and interfere with passing planes.

"I'm asking for some time," said FAA Regional Standards Manager George Aiken, speaking in a conference call during the crowded commission hearing in Sacramento.

The federal agency's late-blooming concerns infuriated San Jose project developer Calpine Corp., which has been trying for nearly a decade to build the plant, and garnered sighs from state commissioners.

"It's unfortunate it's taken this long to wake up the giant in Washington, D.C.," said Commissioner Jeffrey Byron, joining others in asking why the FAA did not weigh in earlier.

In July, a different branch of the FAA indicated in a letter to the commission that the plant would not cause significant air safety problems because pilots could simply be instructed to avoid flying over it.

That was after a months-long review of the project by energy commission staff scientists who concluded the opposite: that the plant should not be built because of unresolved concerns about navigable airspace.

The two commissioners who have been overseeing the project, Byron and John Geesman, overruled their own staff's assessment in August and were going to recommend to the three other commissioners today that the plant be approved anyway.

But Geesman said at the hearing today that his views were based on his "faith and reliance on correspondence" received from the FAA over the summer.

After hearing from Aiken, Geesman said the FAA should be allowed to investigate its concerns in greater detail. The other commissioners agreed to postpone their decision for up to a few weeks but told the federal regulators to hurry up.

"This is completely unprecedented . . . and is not a good way of different government levels to interact," Geesman said.

Patrick Miles, a state aviation safety inspector, said the person who sent the July letter was from the airports division of the FAA, not the flight standards division of the FAA. Miles said the airports division looks primarily at the building itself when reviewing projects.

"It focuses on the height of the structure," Miles said. "It doesn't focus on the emissions that come out."

The FAA wasn't the only agency with last-minute jitters about the Russell City plant this week.

On Tuesday night, the Hayward City Council briefly considered and then backed off of an "emergency" vote to rescind its 2005 support of the Russell City project.

Councilwoman Barbara Halliday said "we certainly know a lot more things" about the plant and the environment than was known a few years ago.

"We have a difficult situation here," Halliday said. "I'm sorry it's come to this."

For the full story, read Thursday's Daily Review.

Matt O'Brien can be reached at 510-293-2473 or mattobrien@dailyreviewonline.com.