UPDATE 1-California PUC approves Sempra's Sunrise Powerlink

(Adds detail, SDG&E comment, possible legal action)

LOS ANGELES, Dec 18 (Reuters) - Sempra Energy's (SRE.N) proposed $2 billion Sunrise Powerlink transmission project received approval on Thursday from the California Public Utilities Commission.

The 123-mile-long, 1,000-megawatt powerline is to open in 2012.

The controversial line -- fought by environmentalists and ratepayer groups -- split the five-member commission as two commissioners made separate proposals.

In the end, commission President Michael Peevey's proposal received a 4-1 "yes" vote from the board. Dissenting was Commissioner Dian Grueneich, who offered a proposal that differed from the one passed by the board, mainly in that it would have enforced a requirement that the line carry a large amount of renewable power.

Peevey and other commissioners said during a commission session held in San Francisco that they were confident Sempra's investor-owned utility, San Diego Gas & Electric Co, would keep oral promises to transit renewable power on the Sunrise Powerlink and that renewables account for a third of the power it delivers by 2020.

Sempra Chief Executive Officer Debra L. Reed said the approval will foster growth of renewable energy.

"Reliable transmission infrastructure is critically needed to reinforce the region's electric system and to open up new avenues for delivering green energy to our customers."

The Sunrise Powerlink is to run from the Imperial Valley to San Diego County.