The proposed SunZia lattice steel towers will be similar in height to these towers near Spearville, Kansas.

The Associated Press

Backers of the SunZia power line in Arizona and New Mexico turn effort to state and local permits.

Officials of the SunZia Transmission Project said Monday that, with federal approval in hand, they'll now turn their efforts towards seeking state and local siting approvals in New Mexico and Arizona.

U.S. Interior Secretary Sally Jewell was joined Saturday by members of New Mexico's congressional delegation and other federal officials to announce the government's approval of the $2 billion SunZia project.

Supporters say the 515-mile-line cutting across south-central Arizona into new Mexico would help deliver more energy to the region and improve the reliability of the existing high-voltage regulatory grid.

The dual power line proposal still needs permits from the Arizona Corporation Commission and the New Mexico Public Regulation Commission. Tucson Electric Power Co. is backing the project.

Opponents of the project, concerned particularly about its potential impacts on the San Pedro River Valley, say they'll fight the state permitting efforts and consider going to court to try to overturn the federal approval. They're also hoping that a lack of demand for power will sink the project.

Project officials say SunZia reached a number of milestones during its federal permitting efforts. Those include designation by the White House as one of only seven transmission projects in the country to receive accelerated permitting treatment, formal sponsorship by the New Mexico Renewable Energy Transmission Authority and initial agreement with Boston-based First Wind Energy to receive "anchor tenant" status.

SunZia will have additional announcements as other developments currently underway reach completion, the company said.

"We are excited to reach this milestone and to be one major step closer to unleashing the renewable energy potential of the southwest and creating jobs," said Tom Wray, SunZia project manager. "Reaching an agreement with the U.S. Department of Defense to take measures to preserve and protect the current and future missions of the White Sands Missile Range was the final hurdle in this process and a huge accomplishment in itself.

"And none of this would have been possible without the exhaustive and thorough environmental review and analysis" by the Bureau of Land Management, Wray said in a statement.

But opponents will consider challenging the adequacy of the federal environmental review of the project because they believe the high-voltage transmission line would destroy previously untouched wildlife habitat and disrupt primary wildlife migration corridors between the Galiuro and Catalina and Rincon Mountains.

"The final route selected by the Bureau of Land Management (BLM) would irreparably harm some of Arizona's most important natural and cultural resources and irreversibly damage a unique and important ecosystem," the Sierra Club and Cascabel Working Group said in a statement. "The damage that this project would do to Arizona's lower San Pedro Valley region cannot be justified given the questionable and unproved claims that this project is needed to promote renewable energy resources."

Opponent Norm Meader of the Cascabel group acknowledged that stopping the SunZia permits won't be easy, and said the most powerful argument against it is that many California utilities won't need to buy more electric power anytime soon.

"We don't think anyone will buy the power," said Meader, of Tucson, who is the Cascabel group's co-chair.

Ian Calkins, a SunZia spokesman, said the company expects to have more leverage in signing up customers now that it has a federal decision in hand, although it's difficult to say when it will have customers firmed up.

"If there was a litmus test for every piece of energy infrastructure, to secure the contracts before you begin permitting efforts, there would be no infrastructure built, or almost none. That's not the way the world works, "Calkins said.

Interior Secretary Jewell told The Associated Press in a telephone interview that New Mexico is blessed with sunshine and wind, but those resources will remain stranded unless investments are made in transmission infrastructure.

"This is a sustainable industry that will create jobs," she said. "It's an opportunity really for the state to make an investment in a future that is not tied to commodity prices, the vagaries of oil and gas prices and the boom-and-bust cycle that is so prevalent in that industry."

But U.S. Rep Steve Pearce, a New Mexico Republican whose congressional district includes the area where the transmission line would be, said the project will permanently damage national security. "Green-lighting the completion of SunZia along the chosen route is a reckless rush to judgment without thorough examination," Pearce said in a statement.

The federal Bureau of Land Management also granted a key federal permit for the project Saturday. SunZia received a "Record of Decision," which marks the end of an effort that started in May 2009.

Concerns over the impact of the project on the White Sands Missile Range in southern New Mexico landed the project in limbo in 2013.

In November, the Bureau of Land Management released its environmental review of a compromise reached with the Defense Department, calling for burying part of the line to avoid interfering with operations at White Sands. Officials were initially concerned the high-voltage line could reduce testing operations at the remote range and ultimately threaten national security.

Includes information from Star reporter Tony Davis and The Associated Press.