Brazilian miner Vale identified concerns around its tailings dams in 2009 and studied but did not implement several steps that could have prevented or lessened the damage from last week's deadly disaster, according to a corporate presentation seen by Reuters.
A tailings dam, used to store the muddy detritus of the mining process, collapsed on Friday, killing at least 84 in one of Brazil's largest industrial accidents on record.
The Brumadinho disaster, coming just over three years after a similar incident at another mine partially controlled by Vale, has fueled calls for a management overhaul and erased more than 70 billion reais ($18.61 billion) in Vale's market value.
But a decade ago, the world's largest iron ore miner was considering ways to use fewer tailings dams, including alternative uses for the waste rock, according to the 73-page presentation.
The presentation pointed to the rising volume of tailings produced at the company's mines, with some locations producing hundreds of thousands of tonnes of tailings daily.
The report suggested Vale make building materials from tailings, including bricks, a step that would give the company another revenue source and lessen the volume needing to be stored using dams.
The 2009 Vale report had recommended the company undertake a project to be called "Zero Dams" that would have involved drying out tailings, among other steps. It was not known whether the report reached the top levels of Vale management nor why it was not implemented.
Vale declined to comment. The report's author, Paulo Ricardo Behrens da Franca, left Vale a year after submitting it and now works as an industry consultant. Reached by Reuters, he did not comment.
Late Tuesday, Vale said it would take as much as 10 percent of its ore output offline in order to decommission 10 more dams like the one that burst last week.