SAN DIEGO -- A plan by San Diego Gas & Electric to build a power line through Anzo-Borrego Desert State Park was tentatively rejected Friday by an administrative law judge, while a utility commissioner tentatively approved an alternate route.

The rulings were both released by the California Public Utilities Commission, which could vote as soon as Dec. 4 on the so-called Sunrise Powerlink Transmission Project.

The utility wants to build a new transmission line about 150 miles from Imperial County, through the park to northwestern San Diego County.

Supporters of the plan say it would bring electricity from renewable energy sources, such as solar and geothermal, that are proposed to be generated in Imperial County.

Opponents say the real reason is to transmit power from a Mexicali plant owned by Sempra Energy -- SD&G's parent company -- to California, and that the Mexican plant doesn't comply with U.S. air quality rules and pollutes Imperial County.

The proposed decision by the administrative law judge denies the Sunrise application, stating that the line is not needed to meet the state's current renewable requirements, and that, if constructed, it could result in significant costs to ratepayers and extensive environmental damage.

Among other things, the judge's proposed decision states SDG&E's service area will not experience a reliability need or "shortfall" until 2014, and the shortfall could be met more economically and reliably by generating more electricity.

The alternate proposed decision sponsored by Commissioner Dian M. Grueneich, the assigned CPUC commissioner in the Sunrise proceeding, approves, with conditions, an alternate route for the power line that avoids the park and all tribal lands.

The alternate proposed decision also concludes that Sunrise is not needed to meet the state's current 20 percent by 2010 renewable energy requirement, but that it will be needed to meet California's greenhouse gas reduction goal to have 33 percent of the state's energy needs met through renewable energy sources.

SDG&E claims it needs the transmission lines to carry power from Imperial County to fill rapidly growing demand in San Diego County.

Backcountry residents and environmentalists strongly oppose the plan, saying it would damage the environment, spoil the area's visual beauty and lower property values.

SDG&E Chief Operating Officer Michael Niggli said the alternate route is a "major milestone" for the Sunrise Powerlink.

"We are pleased the (commissioner's) decision ... agrees the line is needed to import the renewable energy supplies we need to meet California's greenhouse gas emission reduction and renewable energy goals," Niggli said.

Niggli said he hopes the entire commission will eventually support the Sunrise Powerlink.

"After three years of testimony, hearings, public meetings, a formal environmental review, and now both a proposed and alternate decision for the project, we are hopeful the full Commission also will support the Sunrise Powerlink," Niggli said.

Niggli said the alternative route Grueneich supports is also the one SDG&E prefers.

Sen. Christine Kehoe, D-San Diego, said both decisions protect the state park.

"Today marks a victory for the protection of Anza-Borrego Desert State Park and the opportunity for Californians to continue to enjoy the wonders of the California desert," Kehoe said.

The 500 kilovolt line had been planned to run through Anza-Borrego Desert State Park and along Highway 78 past Julian. The southern route avoids those areas.

The CPUC will hear oral arguments regarding the proposed decisions in a meeting in San Fransisco on Nov. 7. A vote could take place on Dec. 4.