SAN FRANCISCO -- The state's Public Utilities Commission approved Pacific Gas & Electric's resubmitted application for a natural gas-fired power plant project in East Contra Costa County, again giving the green light to construction of the 586-megawatt plant.

In a 3-1 vote Thursday afternoon, commissioners approved a purchase and sales agreement for the Oakley Generating Station months after PG&E amended its proposal in response to a state appellate court ruling that the commission's first plant approval was made in haste.

Commissioner Mike Florio abstained from voting, saying he had been involved with the project as an advocate before sitting on the board.

Commissioner Catherine Sandoval cast the lone dissenting vote.

The Oakley power plant will help support the state's policy on having more efficient, environmentally friendly power sources, PUC board president Michael Peevey said. Also, it is ready for construction now rather than the years it could take other projects, he said.

"It adds up to pretty much a slam-dunk case," Peevey said.

"Obviously, we're really pleased with the decision. It will ensure we have flexibility as the state moves toward its new energy goals," PG&E spokesman Jason King said.

Assemblyman Jim Frazier, D-Oakley, Oakley Mayor Kevin Romick and county Supervisor Federal Glover of Pittsburg were among a contingent of about three dozen community members and union workers in favor of the project. Several in the crowd wore bright orange T-shirts reading "Approve Oakley Now."

"This is the best Christmas present for the area," said Greg Feere, chief executive officer for the Contra Costa Building and Construction Trades Council.

Construction of the power plant will create more than 700 jobs and bring millions of dollars into the local economy. At peak operation, the plant will produce enough electricity for about 500,000 homes.

Thursday's decision caps a topsy-turvy five-year process of approvals, reversals and appeals for the power plant, which is planned for 22 acres of industrial property near the Antioch Bridge on Bridgehead Road.

"What's been true then is still true now. It's unnecessary, and it will cost PG&E ratepayers millions of dollars," said Mindy Spatt, a spokeswoman with environment group The Utility Reform Network, or TURN.

TURN, along with environmental groups Californians for Renewable Energy (CARE), Communities for a Better Environment (CBE), Sierra Club and Division of Ratepayer Advocates, have objected to the project. The Public Utilities Commission still has not met the burden of showing that the power plant is needed, said Spatt, adding that the agency decided in April there was no conclusive need for new generation through the year 2020.

The Oakley project was initially approved in December 2010 by the Public Utilities Commission, and some minimal grading work has been done at the site. Six months earlier, that same agency had denied PG&E's application to bring a plant online by 2014 because it wanted to limit the amount of electricity plants were generating.

PG&E now aims to bring the plant online by July 2016. Danville-based Radback Energy Inc. would be responsible for building the plant and selling the plant to the utility once it is up and running.

It remains uncertain if TURN or other groups will take any further action.

"We went to the mat on this one. We haven't had time to consider what, if any, will be our next move," Spatt said.

Radback will wait awhile before restarting construction in case of any further challenges, said Eric Zell, a company spokesman.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.