SAO PAULO – A disaster at one of Vale's tailings dams earlier this year that killed at least 255 people was partially triggered by "a persistently high water level" that caused the dam to lose its strength, according to a report by a panel of experts appointed by Vale's legal advisers.
The report, released by Vale on Thursday, said there was no warning that the dam was unstable, and that no seismic activity or explosions in the area were recorded on the day the dam burst in late January.
The Brumadinho disaster came less than four years after another dam collapse at a joint venture between Vale and BHP Group in the same region, an accident that experts also blamed on water weakening the solid materials composing the dam so that they behave more like a liquid - a phenomenon known as liquefaction.
While prior experience indicates that tailings dams rarely collapse because of a single cause, the disaster in the town of Brumadinho was facilitated by several factors, including poor internal drainage and intense rain that helped cause the excess of water, the four-expert panel said.
Vale and its top executives at the time of the disaster have been assailed by politicians and prosecutors for failing to prevent the disaster despite what critics say were ample warning signs, but the panel's report said there were "no apparent signs of distress prior to failure."
The disaster has weighed heavily on Vale's share price, which is still around 5% lower than the day before the disaster, while the broader Bovespa index has risen 18% to an all-time high.