FLAGSTAFF, Ariz. (AP) — An environmental review for a proposed copper mine in eastern Arizona did not adequately analyze the potential impacts of climate change and the strain that drought and demand have put on water resources in the region, a U.S. Bureau of Land Management report has found.

The U.S. Forest Service asked the Bureau of Land Management earlier this year to quality check its review for the Resolution Copper mine in Superior, about an hour east of Phoenix. The project is vehemently opposed by Native American tribes who hold the land sacred.

Resolution Copper, a joint venture of global mining giants Rio Tinto and BHP, was set to receive a parcel of land in the Tonto National Forest for mining in March 2021. Then, the Biden administration pulled back an environmental review to further consult with tribes. The move prevented the land exchange from moving forward.

As part of that consultation, the Salt River-Pima Maricopa Indian Community asked the Forest Service to have a third party look at the environmental review, with a focus on water. The Bureau of Land Management provided the report to tribes last month, and credited the Forest Service for its work on the massive document.

But the bureau said the document was hard to follow at times and suffered from insufficient evaluation or unsupported conclusions. It focused its own review on broader topics that it found deficient, under-developed or improperly analyzed, it said.

The environmental review fell short on information on water rights in Arizona, whether the mine would pull from a basin where groundwater is regulated in Arizona and the potential for catastrophic weather events that have become hallmarks of climate change, the Bureau of Land Management said.

Higher average temperatures, less overall precipitation, and an increase in wildfires and more groundwater pumping as surface supplies drop weren’t thoroughly addressed, the bureau said.

“Impacts from climate change will have significant ramifications on hydrologic conditions in the project area during both mine operation and the extended recovery period,” the agency’s report read.

Water has long been a concern in a region that’s been mired in drought.

The Bureau of Land Management said the environmental review should do more to help the public understand the permit that allows Resolution Copper to pump groundwater now and into the future — even if mining isn’t green-lit — and how that will affect water sources in the region.

The agency also noted some options for storing mine waste were too quickly dismissed.

Salt River-Pima Maricopa Indian Community President Martin Harvier said he still wants to see an entity independent of the federal government study whether operations at the mine could impact the water sources his community relies on.

“That’s the big concern that we have in the whole state of Arizona with the drought conditions that we’ve been going through for years,” he said. “We’re talking about cutbacks on surface water … our next option is getting water from our aquifers.”

Another tribe, the San Carlos Apache, asked the Forest Service earlier this month to shelve the environmental review and start over.

“The BLM report validates what we have been saying for years,” San Carlos Apache Chairman Terry Rambler said in a statement. “The Resolution mine’s destruction far outweighs its benefits and must not be built.”

Resolution Copper spokesperson Simon Letendre said Tuesday that the Forest Service’s environmental review was rigorous and thorough, and the company is committed to working closely with with government agencies, tribes, community groups and others to ensure the project moves forward safely, respectfully and sustainably.

The U.S. Forest Service said some of the topics raised by the Bureau of Land Management’s report merit further consideration. The agency hasn’t decided whether to re-do or supplement the environmental review, said Forest Service spokeswoman Michelle Burnett.

The release of the environmental review is key to the project. Under federal land, the publication of it starts a 60-day clock for the land to be transferred to Resolution Copper.

Mining wouldn’t happen for at least 10 years even if the Forest Service land ultimately is exchanged for private land elsewhere in the forest, a move made possible by a provision slipped into a must-pass U.S. defense bill in 2014. More than two dozen permits still would be needed.

Arizona Gov. Doug Ducey, the mayor of Superior and others have touted the copper mining project for the 3,700 direct and indirect jobs it’s expected to bring to the state and $1 billion annually to the economy for 60 years. Resolution Copper said the project also could be vital to the transition to clean energy in the U.S. because copper is used in the production of electric vehicles, and wind and solar systems.

Native American tribes have been at the forefront of legal challenges to the project at Oak Flat, largely over religious freedom. The Apaches call the mountainous area Chi’chil Bildagoteel in their language. It has ancient groves, spiritual deities and traditional plants that tribal members say are essential to their religion and culture.

Resolution Copper said it would not deny Apaches access to Oak Flat if it receives the land as long as it’s safe to have people there. Eventually, the mine will swallow the site, using a new process where copper is accessed through deep shafts. Resolution Copper maintains it’s safe and environmentally sound.

Companion bills in the House and Senate aim to overturn the land exchange.

While federal agencies often work together on environmental reviews for projects on federal land, environmental law experts say it’s not common for one federal agency to grade another’s work.

“It seems pretty unusual but not a bad idea to have a quality check and a good thing for the tribes to have asked for,” said Kym Meyer, senior staff attorney with the Southern Environmental Law Center, which is not connected to the project.

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Fonseca covers Indigenous communities on the AP’s Race and Ethnicity team. Follow her on Twitter: @FonsecaAP

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