Brazil: Another dam collapse is possible

Government finds 84 dams in equal or worse shape, risking lives

BRUMADINHO, Brazil — Luiz de Castro was installing lamps at a mining complex in Brazil late last month when a loud blast split the air. He figured it was just a truck tire popping, but a friend knew better.

“No, it’s not that!” the friend said. “Run!”

Dashing up a staircase, caked in mud and pelted by flying rocks, Castro clambered to safety. But as he watched, a wall of mud unleashed by the collapse of a mining dam swallowed his coworkers, he said. At least 154 people, all buried alive.

The deluge of toxic mud stretched for five miles, crushing everything — a tragedy, but hardly a surprise, experts say.

There are 88 mining dams in Brazil built like the one that failed — enormous reservoirs of mining waste held back by little more than walls of sand and silt. And all but four of the dams have been rated by the government as equally vulnerable, or worse.

Even more alarming, at least 28 sit directly uphill from cities or towns, with more than 100,000 people living in especially risky areas if the dams failed, an estimate by the New York Times found.

In the disaster last month, all the elements for catastrophe were there: A reservoir of mining waste built on the cheap, sitting above a town. Overlooked warnings of structural problems that could lead to a collapse. Monitoring equipment broke. And perhaps above all, a country where a powerful mining industry has been free to act more or less unchecked.

The threat of poorly constructed mining dams in Brazil goes far beyond one company. The latest deadly failure — the second in Brazil in three years — has made it clear that neither the mining industry nor regulators have the situation under control.

Vale SA, the world’s largest iron ore producer, says it will close all 10 of its dams in Brazil with a design similar to the one it ran in Brumadinho. Still, the company defended its management of the dam, which had been inactive since 2016.

“The dam had a safety factor in accordance with the world’s best practices,” Vale said in a statement. The structure, it said, had been inspected regularly, and the reports “attest to the physical and hydraulic safety of the dam.”

But questions about the dam’s safety had been brushed aside for years. Despite them, the company had managed to get its plan to expand the mining complex in Brumadinho fast-tracked for approval by local officials.

The solidity of mud

Dams like the one that collapsed in Brumadinho are, in essence, lakes of thick, semihardened mud consisting of water and the solid byproducts of ore mining, known as tailings.

“Basically they are like landfills, but wet landfills,” said Gregory B. Baecher, a member of the National Academy of Engineering and a professor at the University of Maryland.

The dams’ unique construction makes them vulnerable to a bizarre and potentially devastating process called liquefaction. When that happens, a solid material seemingly resting safely in place can abruptly become a murky liquid, flowing downhill and destroying nearly everything in its path.

Even a subtle change, like an increase in water content because of especially heavy rains, say, or poor management, can create enough pressure to push apart the tailings and liquefy the mud.

“The forces are absolutely phenomenal,” said Dirk Van Zyl, a professor of mining engineering at the University of British Columbia, who investigated a 2014 collapse of a tailings dam in Canada. “You really have to see it to understand.”

A looming threat

Two weeks after the Brumadinho tragedy, sirens went off in the night 76 miles away, in Barão de Cocais. “Attention! This is a real dam break emergency,” loudspeakers blasted. “Abandon your homes immediately.”

The alarms wreaked havoc as nearly 500 people were ordered to evacuate. Vale, which owns the mining complex in Barão de Cocais, called it a “preventive measure,” explaining it had initiated its emergency plan after the consulting firm Walm refused to attest to the dam’s stability.

“We hope it doesn’t burst, but unlike many cities we had time to act,” said Décio dos Santos, the mayor. “We didn’t know the dam was dangerous.”

A company town

Given the dearth of government inspectors, companies are allowed to self-regulate, hiring independent auditors to verify dam safety through inspections and an analysis of written records — all provided by the company.

Experts say that creates a conflict of interest. “You can’t have the person doing the inspection getting paid by the company he is inspecting,” said Evandro Moraes da Gama, a professor of engineering at the Federal University of Minas Gerais specializing in mining waste.

Four days after the Brumadinho dam burst, the police arrested the outside inspectors who had attested to its stability. A judge later ordered them released.

“They’re taking it out on the inspectors, arresting them, but it’s the system that’s flawed,” Gama said.