Cleaning the Creek

A mining company mucks out its own mess at Pinto Creek

Tailings are the mess left by mining, what's left after ore is broken into rock or crushed into powder and the metal has been extracted. It has no earthly use, but it has to go someplace, and so the rock gets dumped into unsightly toxic piles and the powder gets sprayed into terraces that resemble Mayan pyramids.

The BHP Copper Pinto Valley mine tailings scar a long ridge five miles west of Miami, Arizona. Anyone who has driven Route 60 from Phoenix to Globe has seen the flesh-colored flat spots on the otherwise dark and craggy skyline. They are called "impoundments" or "ponds" or "dams," because the tailings material is sprayed onto them wet. And though the outside dries into something that looks like dirt, the inside stays wet and viscous like an underdone omelet. Mining folk call that material "plastic slimes," and it makes an unstable base for anything on top of it.

On October 22, 1997, one of the BHP tailings impoundments blew out under pressure from rocky debris loaded on top of it. More than 317,000 cubic yards of mining waste the consistency of toothpaste squeezed from the heap and flowed into Pinto Creek below, filling it rim to rim, 70 feet across and 42 feet deep in some places for three quarters of a mile. Gray liquid oozed and ran from the muck, turning another three-quarter-mile reach downstream into an environmental nightmare.

As if Pinto Creek didn't already have problems.
In 1993, heavy rains had flooded the same impoundment and washed tons of tailings down Pinto Creek, roughly 20 miles to Roosevelt Lake. And for six years, environmentalists had been fighting the imminent Carlota Mine, which will be dug in the creek bed immediately upstream from the October spill.

For three years running, the environmental group American Rivers has placed Pinto Creek high on its list of the nation's most endangered rivers. The U.S. Forest Service nominated its lower reaches for "wild and scenic river" status.

But the mile-and-a-half tailings plug near the creek's source might have destroyed nearly everything wild and scenic about Pinto Creek if the weather had been different--or if BHP, the company responsible for the spill, hadn't immediately opened its wallet.

BHP, a gigantic international mining corporation headquartered in Australia, by now has sunk more than $20 million into a cleanup that may serve as a model for cleaning up future mining disasters. A state mine inspector speculated that the cost may reach $30 million before it's done.

The accident occurred because of a practice that the same mine inspector later called "stupid."

The impoundments were built in the 1970s and 1980s by Magma Copper, the mine's previous owner. There had been no new tailings placed there since 1987.

In the fall of 1996, however, BHP decided to use the tops of impoundments as dumps for another sort of mine waste. Copper ore lies deep underground, and the earth has to be stripped away to get at it. The "overburden" then has to be hauled off. BHP, with the approval of an outside engineering consulting firm, was dumping the overburden on top of the tailings impoundments. Then, after they'd placed as much as they could, they would have graded the rock and revegetated it, making the tailings scars less visible from the road.

Workers had already piled a layer of rock and fill 50 feet deep on the impoundment and were just starting to add a second 50-foot layer when it broke. The soft center simply could not support the weight of the rock dump.

"You put a 10-tiered wedding cake on a base of Jell-O, then something's going to give," says Bill Hawes, assistant state mine inspector.

"I would never want to do anything on a tailings pond more than put a few feet of waste to prevent dust from blowing," Hawes continues. "The next mine code that comes out will forbid that practice from happening."

During the course of the year in which BHP was piling rock on the tailings dam, it suffered many minor fractures, according to one worker. The ground would split open in cracks up to 20 feet across and 100 feet long, exposing the slimes beneath the hardened surface. Engineers checked it every day for stability. No one expected it to blow out completely.

Frank Candelaria was at the highest point of the rock dump on top of the Pinto Valley tailings impoundment when the earth gave way.

He sat behind the wheel of a 190-ton truck, hauling a load across the upper tier, which was about the size of a football field.

"I looked down and all of a sudden it's the Twilight Zone," he says.
The ground in front of him had cracked like thin ice, with fissures silently spiderwebbing out beneath his truck "like one of them earthquake movies."

A wall of crushed rock as plum and level as if built by a mason seemed to shoot up on his right side. In fact, Candelaria and his truck were falling, riding the entire tier like a giant elevator. It dropped 30 feet until it was level with the top of the lower tier.

Time stopped for an instant. Candelaria still hadn't realized what was happening.

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