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Federal Police in Minas Gerais, Brazil, released the forensic report on the cause of the tailings liquefaction that led to the dam collapse at Vale’s (NYSE: VALE) Córrego do Feijão mining complex in Brazil, which killed 270 people two years ago.
The report concluded that the disaster was triggered by vertical perforations in a weak point of the structure.
According to the investigators, the procedure was initiated by Vale five days prior to the rupture with drilling machines that operate with fluid injection. The pressure of these liquids caused dissolution of the stored sediments and subsequent generation of waves, which ended up shaking the dam.
Minas Gerais state is tightening regulations on tailings dams in an effort to avoid further tragedies
Vale previously said that the rupture had been caused by the weight of the tailing itself, associated with rains at the end of 2018.
Federal Police also dismissed the hypothesis that a detonation at a nearby mine would have triggered the liquefaction.
Vale said it “became aware on Friday 26th of the expedition of the Federal Police’s technical expert report on the possible causes of the rupture of Dam I, of the Córrego do Feijão mine, and that “it will evaluate the entire content of the report.”
In September 2019, Brazilian police indicted Vale, the testing service TÜV SÜD and 13 employees of the two companies for producing misleading documents about the safety of the dam. Each of these crimes can yield from 3 years to 6 years, and can reach a total of 18 years in prison.
In January 2020, Vale SA’s former chief executive officer Fabio Schvartsman was charged with homicide.
Vale executives and members of the government of Minas Gerais signed in February a R$ 37.6 billion ($7bn) deal for the reparation of the socio-economic and environmental damage caused by the dam collapse.
Brazil’s Minas Gerais state is tightening regulations on tailings dams in an effort to avoid further tragedies.
The state published a decree setting out obligations for companies to classify dams according to risk, along with decommissioning of existing structures and emergency works.
“This classification is important so that the state system for the environment and water resources (Sisema) can establish inspection and monitoring priorities, focusing on those dams that represent greater potential for environmental and social damage,” the state government said in a release.
Comments
James C
I once had a tailings dam start to fail on me at the Premier Gold Mine (a long time ago). It was an upstream built dam, which naturally is prone to failure from a design point of view. Any injection of fluids into a earth dam, or even pipe breaks, will cause a dam to fail very quickly…it can happen with hours. if the dam was built with the upstream method, that type of dam was never meant to retain water behind it, as opposed to more expensive centreline dams, which are less prone to failure. How did I fix the potential dam failure temporarily? I moved spigotting operations next to the dam face, to roll back water away from the face of the dam, thus saving the dam for that period of time (water pressure and movement was moved from the face of the dam). Then I dewatered the dam fairly rapidly, knowing I had a well established beach along the inner face of the dam from spigotting operations.