A major electricity transmission line through renewables-rich Southern California is under construction, having vanquished all but a few court cases designed to stymie it.

The Sunrise Powerlink transmission line, being built by San Diego Gas & Electric for an estimated $2 billion, will run 120 miles from Imperial County to San Diego, where the local utility is under a state mandate to provide 33 percent of its electricity mix from renewable generation by 2020.

In federal court today, Judge Roger Benitez of the U.S. District Court for the Southern District of California will hear environmental groups' final oral arguments to halt the construction that began last fall. Backcountry Against Dumps and several other local groups are disputing the Bureau of Land Management's 2009 record of decision allowing the line to cross 85 miles of federal public lands, citing potential damage to wildlife and land along the route.

"These large-scale remote projects and the line, none of them are needed because similar projects that are more distributed can be done in the urban basin," said Donna Tisdale, secretary of the Protect Our Communities Foundation, another of the plaintiffs.

Tisdale also cited the expense and uncertainty involved in connecting large-scale renewable generation to the transmission line. Two projects that SDG&E had signed contracts for -- Esmeralda Truckhaven Geothermal's 40-megawatt geothermal plant and Stirling Energy System Inc.'s 750 MW Solar Two concentrated solar project -- have fallen through since SDG&E received permission to build the line.

SDG&E also has not formally committed to using the line strictly for renewables, meaning it could be used for conventional and fossil fuel-generated power.

SDG&E spokeswoman Jennifer Ramp said the utility has signed five other renewables contracts in the Imperial Valley since committing to build the line, totaling 780 MW.

Ramp said the project would prevail over the lawsuit and other obstacles, including two construction accidents earlier this month. A helicopter lifting transmission towers into place dropped one on June 7; three days later, a different tower fell over after being placed, prompting the aircraft's suspension by the Federal Aviation Administration. Ramp said the aircraft had been returned to its manufacturer, Erickson Air-Crane, and that the line is on track to be completed by the middle of 2012.

"There's been more than a dozen legal challenges to Sunrise Powerlink so far, and it has prevailed against all those challenges," she said. "We're confident that the judge will uphold the BLM's environmental review and approval of the decision to build Sunrise Powerlink."

Previous challenges include 12 administrative appeals to the Forest Service over its approval of a 19-mile right of way through the Cleveland National Forest and an appeal to the state Supreme Court over the California Public Utilities Commission's approval.