San Diego Gas & Electric Co. said Tuesday that it cleared a major regulatory hurdle to build a $1.9 billion power transmission line that runs 120 miles from California's Imperial Valley to the city of San Diego.

The U.S. Forest Service said it approved construction of a 19-mile leg through Cleveland National Forest, casting aside objections from environmental groups. The California Public Utilities Commission and the U.S. Bureau of Land Management have already blessed the transmission line, clearing the way for construction to begin later this year.

The Sunrise Powerlink will carry enough power for 650,000 homes when completed in the summer of 2012, according to SDG&E, a unit of San Diego-based Sempra Energy. It will also help wean the utility from gas-fired power plants to rely more on renewable energy sources like solar and wind farms.

The 500-kilovolt line has drawn heavy criticism from environmental groups and residents who say it will blight the landscape and increase the risk of wildfires.

San Diego County Supervisor Dianne Jacob, a staunch opponent, said she was deeply disappointed but not surprised. She turned her attention to opponents who are challenging the project in court.

"The approval ignores the lasting consequences that will result from the line, particularly the severe fire danger," she said. "Although we had hoped for a favorable decision, it has always been my belief that this matter would ultimately be settled by the courts."

The Forest Service said the utility agreed to several changes to limit environmental harm, such as allowing 2.1 miles of new roads instead of 10 miles and reducing the amount of acreage needed to build the line. The agency said it has strict measures to prevent wildfires.

"Throughout the deliberative process, the Forest Service sought to balance California's renewable energy needs with minimizing impacts to the environment to the greatest extent possible," said Will Metz, supervisor of Cleveland National Forest.

SDG&E said the project will generate 400 to 500 construction jobs.

Many in Imperial Valley hope the region's abundance of sunshine and wind drive an economic turnaround. El Centro, the Imperial County seat, has the highest unemployment rate among U.S. metropolitan areas.