Experts have blamed the massive tailings dam rupture at Vale’s Córrego do Feijão iron ore mine in Brumadinho in the Brazilian state of Minas Gerais on drainage problems.
The expert panel highlighted that dam one lacked significant internal drainage, resulting in a high water level in the dam.
It confirmed that no monitoring devices detected precursors to failure.
Heavy tailings contain high iron content and could create stiff tailings and become very brittle if undrained, according to the report.
“The dam’s failure was sudden and abrupt, which was the result of high shear stresses in the downstream slope of the dam and the brittle undrained response of the tailings,” the panel stated in its report on the technical causes of the Feijão Dam One failure.
There was no earthquake or blasting activity recorded, while the dam showed no signs of distress prior to the failure.
The panel noted that experience from previous tailings dam failures showed they were rarely due to one cause.
In the wake of controversy surrounding the Brumadinho tailings dam disaster, Vale then-chief executive Fabio Schvartsman stepped down in March this year.
Media reports alleged that Schvartsman dismissed an email alerting him about the impending failure of the Córrego do Feijão mine’s storage facility.
Vale reported a loss of $US1.6 billion ($2.3 billion) in the March quarter as the dam disaster cut its iron ore supply.