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The giant Resolution Copper mine planned east of Phoenix cannot function without lots of water. And the mining industry’s heavy water usage has come under greater scrutiny as Arizona continues grappling with historic drought.
While the multinational mining company is taking a proactive approach to meet its tremendous water needs, their actions may still have a lasting and severe impact on the local hydrological landscape around Oak Flat.
Resolution Copper needs massive amounts of water – at least 250 billion gallons from the Phoenix Active Management Area over six decades. Right now, they’re busy getting rid of massive amounts of water – pumping out 1.5 million gallons a day since 2009.
But all of that water isn’t being lost.
That underground mine water gets treated on-site, then sent to farmers near the New Magma Irrigation and Drainage District in San Tan Valley. More than 7 billion gallons have been discharged from Resolution Copper’s No. 10 mine shaft since they’re not mining yet.
“That means they don’t have to pump as much,” Resolution Copper President Vicky Peacey told KJZZ. “That saves that amount of groundwater in that area for other future uses. This is just the new way of producing copper.”
Rather than sending this precious resource to farmers in the future, Resolution Copper plans on recycling it for baking copper concentrate. Until then, Peacey says mining is merely one of many necessities competing for water in the Valley.
Warm water drips while steam circulates at the bottom of the No. 10 mine shaft.
Gabriel Pietrorazio/KJZZ
Warm water drips while steam circulates at the bottom of the No. 10 mine shaft.
“We need copper, we need critical minerals,” she added. “We need agriculture. We need home development. We have to coexist with everybody else.”
And by doing so, Resolution Copper, in return, earns long-term storage credits.
Tribal, municipal and industrial users are able to recover a one-time use of an acre-foot for each credit bought, swapped or earned within active management areas – regions where groundwater resources are heavily monitored.
“It’s not like a water right, where you get an amount of water every year,” said Arizona Water Banking Authority General Manager Rebecca Bernat. “That’s very different.”
With more than 4 million acre-feet stored, Arizona Water Banking Authority is the state’s largest single credit holder. Bernat says it’s all based on supply and demand.
“What I’ve noticed looking at the market, many water providers are right now holding on to their credits,” she explained. “They’re not interested in selling them, which makes sense, because they want to make sure they have enough supplies.”
In the past, Resolution Copper purchased long-term storage credits from the Gila River Water Storage – a partnership between utility Salt River Project and the Gila River Indian Community.
The Arizona Department of Water Resources keeps track of who has credits and how many by adding and subtracting balances. In all, Arizona holders have saved up more than 14 million acre-feet, with Resolution Copper making up close to 2% of all long-term storage credits statewide.
The copper mining project has banked more credits by recharging aquifers in central Arizona than Scottsdale, Glendale, Peoria, Avondale, Surprise, Goodyear, Tempe and even the not-for-profit SRP.
Resolution Copper has stored 313,000 acre-feet and counting, but the company estimates it’ll need twice as much: at least 775,000 acre-feet – roughly enough to supply the entire city of Tempe for 15 years.
That banking is voluntary, says Sarah Porter, director of the Kyl Center for Water Policy at Arizona State University.
“They’re not required to do that,” she elaborated. “Resolution is making investments that it is not required to make because of law or permitting. That’s something far beyond what was expected of mines, let’s say, you know, 50 years ago, and the costs for them to do it are not insignificant.”
Dewatering and recycling water is expected to account for less than a third of the mine’s consumption needs. Most of the project’s supply – roughly 540,000 acre-feet – would be pumped from the Desert Wellfield inside the East Salt River Valley.
Mining has always been criticized over water, but Porter believes “we don’t hear that complaint about other industries,” adding “maybe a little bit about groundwater-based agriculture, but industries – by and large – are not held to that standard.”
Resolution Copper's No. 10 shaft, the deepest single lift mine shaft in the U.S., overlooks the Oak Flat campground in the Tonto National Forest.
Gabriel Pietrorazio/KJZZ
Resolution Copper's No. 10, the deepest single-lift mine shaft in the U.S., overlooking the Oak Flat campground.
She insists this mine won’t single-handedly dry up the Valley.
“If you were worried about that story,” Porter stressed, ”you wouldn’t be focusing on Resolution Copper. By the same token, that doesn’t mean that local use of water will have no impacts.”
Superior Community Working Group volunteer Jim Schenck agrees.
“For a town of 3,000, we punch way above our weight to negotiate with a multinational company,” he said. “Anybody that tells you a mine doesn’t have environmental impact is a liar. The issue is, what mitigations can you make, and do they outweigh what will happen?”
The working group is made up of about 25 volunteers from communities along the Copper Corridor, like Top-of-the-World, Kearny and Winkelman.
Schenck, who is also vice president for Legends of Superior Trails and treasurer of the nonprofit Rebuild Superior, says they’ve been testing for chemical traces in water near the project on a quarterly basis since 2017.
He shares they haven’t found anything alarming yet. And funding from Resolution Copper does not affect the group’s independence. “We have our own expert that is paid for by Resolution, but we choose them. They answer to us.”
If mining begins, groundwater levels are expected to drop between 10 and 1,000 feet across 300 square miles. It’s among several concerns raised by environmental geologist James Wells.
“I have respect for mining, frankly,” said Wells, “but this mine is a very glaring candidate for an ore deposit that perhaps should be left alone.”
A map indicating potential in potential declining groundwater levels around the Desert Wellfield within the Phoenix AMA.
James Wells/LEA Environmental, Inc.
A map indicating potential in potential declining groundwater levels around the Desert Wellfield within the Phoenix AMA.
He specializes in hydrology and geochemistry as president and senior geologist for L. Everett and Associates Environmental Inc. in California. His Santa Barbara-based firm focuses on soil and groundwater contamination.
Wells’ research suggests Resolution Copper could draw up to triple the amount of groundwater it’s currently projected to use if the company’s water-saving measures aren’t met. By Resolution’s own estimate, they plan on using only a third of the water needed per ton of ore compared to existing copper mines nationwide.
Wells thinks that’s optimistic.
His firm was hired by the San Carlos Apache Tribe to examine the project’s final environmental impact statement, which was drafted by the U.S. Forest Service. The federal agency declined to answer any of KJZZ’s questions – citing that the Department of Justice should be the primary contact. Roughly 30,000 comments were made while drafting this report – a fifth of which focused on water issues.
“Not to say that I’m perfect at it, but I think in large measure, Resolution and the Forest Service don’t really have answers to my points,” Wells shared, “because I’ve tried to be truthful and honest. They’ve even acknowledged that many of the springs will probably dry up.”
This map identifies groundwater-dependent ecosystems of concern due to possible mining by Resolution Copper.
Final Environmental Impact Statement/U.S. Forest Service
This map identifies groundwater-dependent ecosystems of concern due to possible mining by Resolution Copper.
Wells warns the Apache Leap Tuff Aquifer – which supplies water to sacred natural springs, like Devil’s Canyon, that Apaches use at Oak Flat – is a fragile hydrological system that will be broken due to the land sinking from block cave mining.
It’s a cost-effective method to extract huge deposits by allowing the ore body to collapse on itself. That’ll cause enormous amounts of water to drain deeper into the earth: hundreds of gallons, every minute, for over half a century.
“It’s awfully risky, too,” added Wells, “because there is a kind of an unquantifiable uncertainty as to the extent of the subsidence. But once the mining is completed, that subsidence is uncontrollable. They can’t stop it.”
Not to mention, large-scale mining leads to massive tailings. Resolution Copper told KJZZ it expects to produce roughly 1.3 billion tons of tailings over the mine’s lifespan to generate 40 billion pounds of copper from the behemoth ore body.
This map depicts the size and scale of the entire proposed Resolution Copper mining project.
Final Environmental Impact Statement/U.S. Forest Service
This map depicts the size and scale of the entire proposed Resolution Copper mining project.
“Everything is super-sized,” Wells emphasized. “It’s a very, very big operation, and therefore the impacts are multiplied as well.”
So, too, is the period of time needed post-mine closure to replenish hundreds of billions of gallons depleted from aquifers. Resolution Copper admits it’ll take a millennium for the groundwater to reach equilibrium, with Wells adding “in terms of our lifetimes, these are very significant and persistent impacts.”
* Resolution Copper wants to dig up a massive amount of copper ore beneath Oak Flat inside the Tonto National Forest. And by doing so, a site that some Apaches consider sacred may be destroyed.
While they’re not mining yet, Resolution Copper is slowly digging its way toward the lucrative ore. In fact, the site is already home to the deepest single-lift mine shaft in North America, and KJZZ’s Gabriel Pietrorazio goes thousands of feet underground to see it for himself.
Oak Flat — an area east of the Valley — may soon be home to a massive copper mine. It holds cultural and spiritual significance to many Apaches, whose ancestors were forced off the land by the U.S. military.
Discovered in Arizona’s Copper Triangle, Oak Flat is home to one of the richest copper deposits in the world. But the battle to mine there — about 60 miles east of Phoenix — has been bogged down by decades of politics.
Watch a KJZZ panel discussion about Oak Flat — an area sacred to generations of Apaches that may soon be home to one of the largest copper mines in the world.