The SunZia project's road to commercial operation is facing a new round of controversy, this time from community groups that fear the transmission line from New Mexico to Arizona will inflict irreparable environmental damage.

The $2 billion project, first proposed in 2008, looks to build two 1,500-megawatt high-voltage lines running 520 miles from central New Mexico to Arizona to carry wind-generated electricity to Western markets, the Albuquerque Journal reported .

Opponents of the project question how much renewable energy it would actually transport, whether wind developers using the line can realistically find markets for up to 3,000 megawatts of wind-generated electricity, and whether the benefits for New Mexicans are worth the costs.

The project has received licenses and permits in Arizona. But it still needs approvals from the New Mexico Public Regulation Commission, the State Land Office, the Middle Rio Grande Conservancy District and the Army Corps of Engineers.

The U.S. Bureau of Land Management also must approve SunZia's plan of development for construction, including detailed avian protection and migratory bird conservation measures along the Rio Grande, before allowing the project to proceed.

High on the list of community concerns is the project's proposed river crossing at Escondida, near Socorro. Opponents fear it would be a death trap for migratory birds that forage and roost in the area, because it would cross a narrow passage between two wildlife refuges — Sevilleta National Wildlife Refuge to the north and Bosque del Apache to the south — said Cecilia Rosacker, executive director of the Rio Grande Agricultural Land Trust.

"That's some of the last wetlands left in New Mexico, and it's critical to continental bird migration," Rosacker said. "We've been working 20 years on the local level to protect birds, including endangered species."

The U.S. Fish and Wildlife Service estimates that between 8 million and 57 million birds are killed nationwide every year when they hit electric utility lines.

The Bureau of Land Management and Fish and Wildlife did review about a half-dozen proposed crossings south and north of Escondida, including a detailed study at San Antonio, near Bosque del Apache. It concluded that crossing at the narrowest point, near Escondida, would have the least impact.

The Bureau of Land Management is also reviewing the precise location of the river crossing, said Melanie Barnes, the agency's state director for resources.

That process will include public input, Barnes said.

The Associated Press contributed to this report.