SunZia Map

The 500-kV, 520-mile SunZia transmission line is expected to deliver renewable energy from resources in New Mexico and Arizona to load centers farther west beginning in 2024. 

A 520-mile high-voltage transmission line in New Mexico and Arizona that received federal right-of-way approval in 2016 is reopening its National Environmental Protection Act process with a plan to be operational by 2024.

The U.S. Department of the Interior in a January 2015 record of decision approved a route for the bidirectional, 500-kV SunZia Southwest Transmission Project to deliver high-quality wind generation resources from New Mexico through Arizona and into Southern California via the Palo Verde Hub. The Arizona Corporation Commission in 2016 approved a certificate of environmental compatibility for the 200 miles of SunZia that would run through that state. The New Mexico Public Regulation Commission in 2018 also approved rights of way for the project, but denied without prejudice its location in order to accommodate some private landowners, Tom Wray, project manager for SunZia, said in a telephone interview (see CEM No. 1509).

Since that time, Wray said, the project's developer, SouthWestern Power Group, has worked with community members, public and private landowners, nongovernment organizations, state and county officials and the U.S. Department of Defense to address concerns regarding the line's route in New Mexico. As approved by Interior, SunZia's New Mexico route runs through the Northern Call Up Area adjacent to White Sands Missile Range, where the Department of Defense sometimes runs low-profile test missions, Wray said, noting the approved route does not actually run through the range. It also crosses the Rio Grande near Socorro at a critical point for migratory birds, including the sandhill crane.

The objective, Wray said, is to get an alignment that better addresses DOD concerns by going a little farther north, where the line would not cross the testing area, which requires a new NEPA process.

"This is a voluntary effort on our part to cooperate with White Sands and the Department of Defense," Wray said. SWPG recently restarted the NEPA process with the U.S. Bureau of Land Management's New Mexico office, and expects it to last about 14 to 16 months, he said.

The new plan will not affect SunZia's route through Arizona, so there is no need to revisit permitting in that state, Wray said. SWPG will return to the NMPRC to seek location approval after completing the NEPA and getting new approval from Interior. Meanwhile, SWPG is finalizing right-of-way permission from remaining private landowners and working with the New Mexico Department of Fish and Game, the U.S. Wildlife Service, local officials and NGOs to mitigate the project's impact on migratory birds.

"I think it will be a better outcome for all parties," Wray said. SWPG is working with the University of New Mexico and others on studies to minimize avian fatalities. They are considering bird diverters and infrared lighting technology that shows promise in preventing larger birds such as cranes from colliding with static lines even in low-visibility conditions.

SWPG is also purchasing property in an effort to establish feeding areas closer to the river that could reduce bird movement during the day. Sandhill cranes usually roost on sandbars in the river to avoid predators at night, Wray explained. They leave to eat in the morning and return again to roost overnight. Limiting movement by bringing roosting and feeding closer together could reduce the chance of collision, he said. Proposals to underground the line at the river crossing were determined to have a more significant environmental impact than mitigation strategies due to the intrusiveness of that type of construction, Wray said.

SunZia is approved for 1,500 MW of transmission capacity per line with a transfer capacity of up to 4,500 MW. "That will get a lot of renewable energy to market in Arizona and California," Wray said, "and that's what we're aiming to do."

The line is set to deliver power from its anchor tenant and first customer, Pattern Energy's 300,000-acre Corona Wind Projects currently under development in east central New Mexico. Construction is scheduled to begin in 2022 if all remaining permitting hurdles have been cleared, and the line will go into operation in 2024—18 years after it was first conceived.