Skip to content
View Featured Image

Tribes Say SunZia Line Threatens San Pedro River, Sue To Stop Work

Above photo: The San Pedro River as seen on April 15, 2023, near Hereford Bridge, south of Sierra Vista.

Mark Henle/The Republic.

The two tribes and conservation groups say the federal government should have considered an alternate route for the power line.

Two Arizona tribes filed a lawsuit against the U.S. Department of the Interior and the Bureau of Land Management for approving a high-voltage transmission line, alleging the government failed to account for historic and cultural sites through the line’s San Pedro Valley route.

The Tohono O’odham Nation and the San Carlos Apache Tribe, along with Archaeology Southwest and the Center for Biological Diversity, filed the suit on Jan. 17 over the authorization of the SunZia transmission line.

The plaintiffs want a federal court to halt construction and require the BLM to comply with the law before continuing further activity.

Fifty miles of the transmission line will traverse the middle and lower San Pedro Valley, which has ecological and historical values that Indigenous tribes and conservation groups hope to protect.

“For more than a decade, the San Carlos Apache Tribe and others have been raising alarms about the need to protect the cultural resources in the San Pedro Valley from impacts of the SunZia project,” said San Carlos Apache Chairman Terry Rambler.

The tribes claim the agencies violated the National Historic Preservation Act, the Administrative Procedure Act and multiple executive orders on historic preservation and tribal consultation.

Developed by Canadian-owned Pattern Energy, the SunZia project is a 550-mile transmission line that will carry renewable energy from central New Mexico, through Arizona and into California.

Tribes and conservation groups say the historic and ecological treasures in the San Pedro Valley are at risk and believe alternative routes should be explored to avoid their destruction.

“They must change course, immediately stop all ground-clearing activity and work with us to protect these sites as required by federal law,” said Tohono O’odham Nation Chairman Verlon Jose.

What Is The SunZia Transmission Line?

The Biden administration has described the $11 billion transmission line as a “game-changer” for America’s transition to clean energy.

It is one of the largest infrastructure undertakings in America, originating at a substation in Torrance County, New Mexico, and ending at the Pinal Central Substation in Arizona. It will bring clean power to 3 million Americans.

The project, first introduced in 2006, will include two 500-kilovolt transmission lines traversing federal, state and private lands in Cochise, Graham, Greenlee, Pima and Pinal counties, bringing energy to markets in Arizona and California.

The transmission line will deliver power generated by Pattern Energy’s SunZia wind facility in New Mexico.

“Since 2009, the SunZia Transmission team has actively worked with BLM and participating tribes to identify and address any impacts to cultural resource properties,” said Natalie McCue, assistant vice president of environmental and permitting at Pattern Energy.

McCue said Pattern has conducted site visits, completed intensive cultural resource surveys with tribal participation, altered designs to avoid or minimize impacts and agreed to protective measures under Historic Properties Treatment Plans to mitigate effects to identified cultural resources.

“The time has passed to reconsider the route, which was approved in 2015 after a robust and comprehensive review process,” she said.

The transmission project broke ground on Sept. 1 after receiving a limited notice to proceed from the BLM. The agency briefly paused construction in November after receiving complaints from the tribes about a lack of formal consultation before work began.

The temporary suspension was lifted on Nov. 29, and the BLM planned to consult with tribal leaders to mitigate SunZia’s impacts on the land.

McCue said Pattern will “avoid, minimize, restore and mitigate any adverse impacts to historic properties.”

Tribes Believe SunZia Will Damage Sacred Lands

Bulldozers have begun clearing land for access roads and 195-foot-tall towers, and tribes say the work endangers cultural sites and sacred areas despite their complaints for over a decade.

The valley is a site of importance to the Tohono O’odham, Hopi, Zuni and Western Apache tribes.

“Tribes are some of the leading supporters of alternative energy solutions. However, there has been a pattern of bad faith going back many years,” said Jose of the Tohono O’odham Nation.

Beyond the Tohono O’odham Nation and San Carlos Apache Tribe’s reservation lands, both tribes say they have deep connections to their broader ancestral territories in the San Pedro Valley.

John Welch, the director of the landscape and site preservation program for Archaeology Southwest, says the San Pedro Valley is rich with archaeological areas and places of great historical and religious importance to the tribes, including landforms, mesas, springs and specific sites named by the tribes.

The National Historic Preservation Act protects historical and cultural sites, stating that such sites “give a sense of orientation to the American people.”

According to Section 106 of the act, federal agencies must consider projects’ effects on historic sites. If historic properties are likely to be affected, the agency must conduct a review and allow interested parties and the public to weigh in.

The plaintiffs claim they have repeatedly asked the BLM to conduct an inventory of historic properties and cultural resources in consultation with the tribes before approving the project.  They believe the BLM has proceeded based on a “deeply flawed” consultation process.

“The BLM got a group of archaeologists to walk down the right-of-way and look for artifacts instead of doing what they’re supposed to do, to take into consideration the broad context of the place’s history and the ongoing connections to living communities,” Welch said.

Environmental Implications And Alternative Routes

The tribes and conservation groups believe the project will destroy the ecological integrity of the landscape in addition to cultural sites, and believe an alternative path is available.

The San Pedro River is one of the last free-flowing rivers in the Southwest and contains essential habitat and riparian areas for wildlife.

In a 2022 environmental impact statement, the BLM found SunZia could accelerate habitat loss, affect conditions for migratory birds and remove riparian vegetation used for habitat and food for wildlife.

The riparian area is home to more than 60 mammal species, 14 fish species and 41 reptile and amphibian species, some of which are endangered or threatened.

According to Robin Silver, co-founder of the Center for Biological Diversity, the San Pedro River is a rest stop for migratory birds. The valley provides a canopied desert riparian habitat, and it is one of the few remaining in the Southwest.

He worries power lines could be an impediment to their movement, and that access roads will cause erosion and sedimentation in the valley.

“We’re talking about an incredibly rare area of Arizona where you can see a vast area of open space that’s not been grossly impacted by human development,” Silver said. “There are alternative routes that cause less environmental damage, particularly the Tucson corridor.”

Conservationists believe there are alternative paths for the SunZia power line that do not negatively affect important cultural and ecological areas. They believe the BLM and Pattern Energy should route the power line through land already degraded by infrastructure.

They believe the project was planned through the San Pedro Valley because it would be more cost-effective than building through the Tucson corridor.

“Why would we sacrifice one of America’s last great places for a power line when we don’t have to do it? It’s not the only way,” Welch said.

Hayleigh Evans covers environmental issues for The Arizona Republic and Send tips or questions to

Sign Up To Our Daily Digest

Independent media outlets are being suppressed and dropped by corporations like Google, Facebook and Twitter. Sign up for our daily email digest before it’s too late so you don’t miss the latest movement news.