U.S. needs minerals for green tech, but planned mines could threaten water

The Resolution Copper mine, not far from Superior, Ariz., would use billions of gallons of water from the Phoenix region over the next 40 years. Water supplies in this region are under increasing stress from drought and climate change.

Julia Simon/NPR

SUPERIOR, Ariz. — On a 107 degree morning in the mountains east of Phoenix, a miner in a hard hat plunges down the nearly 7,000-foot shaft of what may soon be the biggest underground copper mine in the United States.

But for now, the Resolution Copper mine isn’t taking out copper. It’s taking out groundwater, at a rate of around 600 gallons per minute. Because this copper is so deep underground, in geologic formations dating back more than a billion years, the mining takes place far below the water table. The mine is removing that aquifer water so the operations don’t flood. And the mine is giving away this water for free to nearby farmers, about 6 billion gallons so far.

This summer, Arizona state officials declared they won’t permit some new home construction in the Phoenix region because of concerns about groundwater. The region’s groundwater supplies are under increasing stress from drought and climate change. But it’s in that same Phoenix metro region where Resolution plans to remove groundwater for its mining operations. If the mine gets its environmental permits and begins full operations, Resolution would use billions of gallons of local groundwater and stored Colorado River water for the next 40 years.

The U.S. is pushing to secure new domestic mining supplies for metals such as copper, lithium and manganese that are critical for building things like electric vehicle batteries, solar panels and other components of the energy transition away from…