For months, inspectors worried about the safety of a giant mine-dam perched over a town in Brazil but blessed it anyway
By Patricia Kowsmann, Samantha Pearson, Scott Patterson andLuciana Magalhaes
Feb. 24, 2019 6:26 p.m. ET
Employees at Brazil’s mining giant Vale SA and its contract safety inspectors knew for months of dangerous conditions at the mine-waste dam that collapsed last month.
Yet inspectors certified the dam as safe, expressing worry about losing contracts with Vale, the dam owner and a major client, according to police, government prosecutors, court documents, arrest warrants and people familiar with the matter.
On Jan. 25, the structure, called Dam 1, burst, unleashing a tsunami of thick, reddish mud that killed 179 people, mostly Vale workers and contractors. An additional 131 people are missing and presumed dead. It was the deadliest mining disaster of its type in more than 50 years.
Prosecutors looking into the cause of the dam’s collapse are focused on the tight relationship between Vale and TÜV SÜD, the German certifications firm hired to conduct audits of the dam’s safety. There is little oversight of ties between safety auditors and mining companies around the world, experts say. Mine-safety rules in Brazil are especially lax and do little to prevent cozy relationships that can tempt inspection firms to mask dangers.
TÜV SÜD employees expressed concerns about the safety of the dam in emails and their reports to Vale. Inspectors nonetheless continued to sign off on safety audits.
During audits in June and September, Makoto Namba, a senior engineering inspector at TÜV SÜD, and other inspectors found evidence indicating potentially risky conditions at the 280-foot-high dam, which for more than four decades had loomed over the small town of Brumadinho, holding back more than 11 million cubic meters of mine waste.
A safety auditor’s field inspection of the dam in 2017 called attention to potential problems.
Potential indication of
tailings washed out of dam
Water built up
Water channel crack
Source: TÜV SÜD audit report
“Everything suggests [the dam] won’t pass” a key safety test, wrote Mr. Namba in May 2018, a day before a scheduled meeting with Vale to discuss some findings, in an email cited by a judge who signed arrest warrants in the case.
Mr. Namba, 62 years old, later told police he felt pressured by a Vale official to sign a safety certification. Without his signature, Vale would have to halt its adjacent mining operations, which last year were estimated to have produced more than $1 million a day in iron ore. Hundreds of people could have lost jobs. It also would have triggered a mass evacuation.
Mr. Namba and other inspectors voiced worries that Vale would cut off work in retaliation if they didn’t certify the dam as safe, according to his police testimony and emails cited by prosecutors. Mr. Namba also worried that failing to sign would jeopardize his career with TÜV SÜD’s Brazilian unit, according to a person close to his company. TÜV SÜD had contracts for safety audits at 30 other Vale dams in Brazil, as well as new projects at Dam 1.
“Is TÜV SÜD going to sign the safety declaration or not?” Vale executive Alexandre Campanha demanded to know during one meeting, according to Mr. Namba’s testimony to police.
On Sept. 26, Mr. Namba signed it. His lawyer said he did because he believed the dam was safe.
Brazilian police raided Vale and TÜV SÜD offices and arrested 13 employees of the two companies, including Mr. Namba and Mr. Campanha. Eight Vale employees were arrested on Feb. 15 and remain in custody on suspicion of murder. Mr. Namba, another TÜV SÜD engineer and three Vale employees, all arrested in January, have been released. No charges have been filed.
Both companies said they were cooperating in the investigation and were conducting their own probes. TÜV SÜD declined to comment on the firm’s relationship with Vale, but in a statement said there was “heightened uncertainty” about whether the system of safety audits in Brazil provided a reliable declaration of the stability of a dam. TÜV SÜD said it wouldn’t issue any new declarations to Vale until a review of the system has been completed.
A Vale spokeswoman said the company trusts the conduct of the contractors it hires and the employees of those contractors: “Vale is committed to the safety of its structures and has a structured system to manage the dams that includes several technical and governance actions.”
In Brazil, a country bigger than the contiguous U.S., more than a third of mine-waste dams are in an area about the size of Connecticut. All of Vale’s dams similar to Dam 1, known as upstream dams, are in this area.
In August, a month before signing off on the dam’s stability, Mr. Namba won an award from a local trade association for a project he and two other TÜV SÜD inspectors had written with two Vale managers responsible for the dam. The trade group called it pioneering work on managing risk for mining dams.
Another co-author of the study: Arsênio Negro Jr., a senior TÜV SÜD employee, sent emails last May to colleagues toying with the idea of distorting some inspection results about Dam 1 to protect another Vale contract there, according to the arrest warrant signed by a judge in the case.
Mr. Negro Jr., who wasn’t arrested, declined to comment. Mr. Campanha, among those still in custody, has denied wrongdoing and, according to his lawyer, said he didn’t pressure Mr. Namba to sign off on the safety audit.
“From the emails you notice there was collusion between some Vale employees and some TÜV SÜD employees in a way that it was presented to state and federal authorities stability declarations that didn’t directly reflect the critical situation,” William Garcia Pinto Coelho, the lead prosecutor, said at a Feb. 15 news conference.
Authorities gathered evidence that “shows in a very convincing way that this was not an accident,” he said, given both Vale and TÜV SÜD employees had access to information that showed “the critical state” of the dam. Prosecutors alleged Vale employees didn’t act on information it had about the safety risks.
Dam 1 was part of Vale’s Córrego do Feijão iron-ore mine. It was built to house mining waste or tailings—dirt, rocks and bits of ore that are dumped and kept in place behind a dike. As the waste accumulates, the dike is built up with rock, sand and dirt from tailings in stair-step fashion, to a height of nearly 30 stories at Dam 1.
Water is the enemy of these dams, with many failures related to excess moisture. Keeping a watch on water levels and draining the excess is crucial, especially during the region’s rainy season from December through February.
If the mine waste gets too wet, the innards of the dam risk liquefaction, a trick of physics that makes solids behave like liquids. A poorly drained dam has a higher risk of liquefaction, which can collapse a dam’s wall, releasing a river of rock, mud and sludge.
Dam 1 broke open around lunchtime. Lieuzo Luiz dos Santos, a Vale contractor, was drilling holes that day to sink new water-measuring instruments.
Mr. dos Santos and two longtime colleagues had joined a security officer and a construction inspector at the site in good spirits, he said, talking about their Friday night plans. At about 12:30 p.m., he turned off his drilling machine.
While stepping off, he noticed the machine start to move. He thought it was from the wind. Then Mr. dos Santos heard what sounded like an explosion. He looked down and saw the earth open beneath him. He landed on a patch of solid ground inside the rupture and saw one of his colleagues “disappear in a wave of mud.” Then he passed out.
A wall of mining waste crashed into Vale’s crowded lunchroom, below the dam, and engulfed a nearby hotel and homes, traveling as fast as 50 miles an hour.
“It was God’s hand that took me down from there,” said Mr. dos Santos, a 55-year-old father of three, who escaped with a leg fracture. He was rescued from the dam’s remains by helicopter.
“I was lucky,” he said.
Brazil’s National Mining Agency employs 34 field inspectors—but only 20 who specialize in dams—to oversee about 770 mine dams across the country.
That gives Vale and other mining companies wide latitude to use independent auditors such as TÜV SÜD. Brazil’s mining regulator director, Eduardo Leão, said there was no problem as long as safety auditors aren’t owned by the mining company.
”In Brazil, this is what independent means,” said Mr. Leão, a former Vale employee.
The Mining Association of Canada, in what is regarded as benchmark for the industry, recommends that safety inspectors keep an arm’s-length relationship with clients. Just like a financial auditor, such independence is supposed to prevent inspectors from compromising their objectivity to keep company doors open to future contracts.
Prosecutors are investigating whether financial incentives contributed to the safety certification of Dam 1. While TÜV SÜD was performing the dam audit, the firm received new Vale contracts, according to Andre Yassuda, a senior engineer at the firm, in testimony to police. The firm was hired to install equipment at the dam, for instance, and to consult on its eventual closure, Mr. Yassuda told police.
Vale is cooperating with investigators, the company said. Safety certifications signed by TÜV SÜD employees are evidence their executives thought their dam was safe, the company said.
“We were surprised,” said Vale Chief Executive Fabio Schvartsman, speaking at a news conference hours after the dam burst. “It’s because we have certificates from external audits, carried out by specialized companies, even German companies, that guaranteed its stability.”
Augusto de Arruda Botelho, the lawyer representing Messrs. Namba and Yassuda, said the reports they signed “attested to the stability of the dam and reflected, based on data provided by Vale, the situation of [the dam] at the time they signed the reports.”
The inspectors used instruments and internationally recognized criteria to attest the dam was within the minimum stability limits, the lawyer said, “even though the implementation of a series of recommendations was necessary.”
The dam began drawing scrutiny from engineers in 2010. That year, a Vale engineer published an analysis of its vulnerability to liquefaction as his master’s thesis. The paper concluded the dam was stable, but only if spared from shocks such as earthquakes, and its internal water levels were controlled.
Vale has said water levels at the dam were stable and had been in decline over the year leading up to its failure.
Around that time, Vale was closing down some of its older mines. In 2012, it hired a local consulting company, Bureau de Projetos e Consultoria, to help. Vale asked the company to come up with a plan to close down Dam 1 and remove the waste. When ore prices slumped, Vale put the project on hold, Mr. Yassuda told police.
A year later, TÜV SÜD acquired Bureau and took over its projects. The firm’s former owners, including Messrs. Yassuda and Negro Jr., moved to TÜV SÜD, along with Mr. Namba, a longtime colleague.
Pass or fail
Less than 100 miles from Dam 1, a mine-waste dam operated by a Vale joint venture collapsed in 2015 in the town of Mariana, killing 19 people.
An independent report concluded it had collapsed through liquefaction. Over the years, construction errors in the dam’s drainage system, as well as mistakes in the way that mining waste was deposited, had left the dam so unstable that three minor seismic shocks brought it down.
As part of its pledge to prevent a similar disaster, Vale revived plans to close Dam 1. The company stopped dumping mine waste there in 2016. Earlier, Vale had applied for permission to reclaim the remaining iron ore from the mass of waste before dismantling the dam.
How Tailings Are Formed
Tailings are what’s left over after mining companies extract valuable metals from raw ore. This waste can pose a great risk to ecosystems and communities where it is stored.
2. Water and sometimes chemicals are added to the milled rock to separate the metal.
3. Once the metal is extracted, the tailings that remain are in the form of a slurry…
4. …that is pumped into a reservoir with a dam designed to store them indefinitely.
1. Rock containing a desired metal is mined from the earth and finely ground.
Vale looked for a contractor to conduct an in-depth safety inspection as the company awaited permission from the state’s environmental authority to empty and decommission the dam.
Under safety rules approved after the Mariana disaster, Vale needed regular safety audits of Dam 1. In June of 2017, it chose TÜV SÜD.
The contract was a coup for the firm, and for Mr. Namba. He had worked long hours to sign Vale as a client, according to a person close to him.
On a sunny morning in August 2017, a TÜV SÜD auditor, accompanied by four Vale employees, inspected the crest of Dam 1. The grass covering the dam was trimmed, and drainage canals were cleaned.
Types of Tailings Dams
As the volume of tailings grows, new levels of the dam—often made of sandy, dried tailings—are added to increase its capacity.
In the upstream design, these new embankments rest directly upon the ’beach’ inside the reservoir. This saves money, since it requires little earthmoving.
In the centerline and downstream designs, new levels of the dam are placed atop previous levels and built outward. This results in a bulkier—and often sturdier—structure.
As the group moved toward the base of the dam, the inspector noted cracks in water drainage channels, according to a field report. These channels, essentially gullies dug into the top of the dam, direct rainwater off the structure to prevent seepage into the stored waste.
The inspector also noted a high level of water in an area next to internal drainage pipes. Part of the base of the dam slumped toward the adjacent road, a sign of possible erosion, experts said. Wooden beams patched a rupture on the face of the dam.
As part of its certification process, TÜV SÜD conducted a liquefaction study—a test that could help determine the dam’s vulnerability to collapse.
In May 2018, a day before a scheduled meeting with Vale to discuss the findings, Mr. Namba sent an email to other members of his safety-audit team, according to prosecutors: The results of the liquefaction test weren’t good.
Part of the dam didn’t attain even a minimum rating for stability, he wrote. “As such, strictly speaking, we cannot sign the Stability Condition Statement,” Mr. Namba wrote, referring to the official document certifying the dam was safe.
Felipe Rocha, one of Vale’s risk managers, already knew the dam might fail the safety audit, Mr. Namba wrote in emails cited by the judge. Mr. Rocha, one of the co-authors of the award-winning report on risk management, had called Mr. Namba, promising to make repairs to improve its stability.
Tailings Dam Risks
Rate of rise
Water is a tailings dam’s worst enemy. If it saturates the dam walls or the tailings beneath an upstream dam, the whole structure can liquefy and slide. Wetter tailings also travel farther and faster if they escape, causing more destruction.
Upstream tailings dams should be raised slowly, to allow the solid tailings time to dry and consolidate enough to support a new level of the dam.
Height and angle
An undetected layer of clay or silt beneath a tailings dam can prove disastrous. In addition to being less sturdy than rock or sand, such materials drain poorly, allowing water to silently infiltrate the dam.
The taller the dam, the greater the catastrophe if it fails. The steeper the dam, the greater the risk. For an upstream dam made from tailings themselves, engineers recommend a 25% gradient—flat enough to walk up.
Mr. Rocha told Mr. Namba that a different auditor had recently agreed to sign off on another dam’s stability report, despite not passing the liquefaction study, on the promise that Vale would carry out the necessary remedial measures, according to Mr. Rocha’s email.
Mr. Rocha is among the Vale employees still in custody. Through his lawyer, Mr. Rocha denied wrongdoing and said he didn’t pressure Mr. Namba.
Mr. Yassuda of TÜV SÜD signed off on the June safety declaration. While the audit noted multiple problems, including related to water drainage, it concluded the dam was stable.
In the following months, Vale worked to address water problems. On June 11, during the installation of a drainage pipe near the right side of the dam’s base, water started gushing out, according to Vale employees cited in a TÜV SÜD report. The water carried what looked like tailings—mine waste that is supposed to remain dry and stable inside the dam.
Vale stopped work and sealed the hole. Two instruments immediately detected a rapid rise in water levels, but Vale said levels returned to normal by evening. In July, TÜV SÜD field inspectors found a buildup of mineral material at some of the dam’s new pipe exits, which experts said could have been another sign of erosion.
In early September, Mr. Namba’s team was finishing a second audit, based on his firm’s June report and the July field inspection.
The team again reported persistent problems with water drainage, the audit said. Some of the problems were caused by faulty workmanship.
“Not all drains had siphons to prevent air entry,” the report said. “In some cases, even though there were siphons, they were installed upside down.”
The audit report noted that some previously reported problems remained unresolved. It referred again to the liquefaction study in May that showed a high risk of collapse if the water wasn’t sufficiently drained. The report concluded that safety levels were within acceptable parameters.
Vale said the audit didn’t raise problems, but instead made recommendations, which it followed.
Later in September, after the audit was completed, Mr. Namba certified the dam as stable. That month, Mr. Namba’s firm won a contract to help Vale dismantle the aged dam without disrupting mining operations.
On Jan. 10, automated instruments monitored by TÜV SÜD that track water levels gave readings that, if confirmed by an inspection team, would have initiated evacuations, according to testimony by Vale employees, prosecutors said. No inspection team was sent.
Vale said it became aware of the problem on Jan. 21 and that the issue was resolved. It was related to mis-readings, the company spokeswoman said, rather than a water problem.
An email exchange between Vale and TÜV SÜD, however, showed they were still struggling with the episode three days later.
“The readings are incoherent. Please check what happened,” a Vale official said by email to TÜV SÜD and another contractor on Jan. 24: “Prioritize this!”
The next day, the dam burst. Brazil’s National Water Agency said Thursday that mine sediment had been found as far as 119 miles away.
— Alistair MacDonald contributed to this article.
Appeared in the February 25, 2019, print edition as ‘Inspectors Knew of Troubles at Brazil Dam.’
Fonte: The Wall Street Journal