Vale knew deadly Brazil dam at extra risk

The dam collapse at the Corrego do Feijao mine in Brumadinho killed at least 165 people.
The dam collapse at the Corrego do Feijao mine in Brumadinho killed at least 165 people.

Vale SA, the world's largest iron ore miner, knew last year that the dam in Brazil that collapsed in January and killed at least 165 people had a heightened risk of rupturing, according to an internal document.

The report, dated October 3 2018, shows Vale classified Dam 1 at the Corrego do Feijao mine in Brumadinho as two times more likely to fail than the maximum level of risk tolerated under the company's own dam safety policy.

Vale previously cited an independent audit last year declaring the dam safe and said equipment showed the structure was stable weeks before the collapse.

The previously unreported document, seen by Reuters, is the first evidence Vale was concerned about the safety of the dam.

It raises questions as to why the audit around the same time guaranteed the dam's stability and why the miner did not take precautions, such as moving a company canteen downhill from the structure.

Entitled "Geotechnical Risk Management Results," Vale's internal October report placed the Brumadinho dam within an "attention zone," saying that "all prevention and mitigation controls" should be applied.

A failure could cost the company $US1.5 billion ($A2.1 billion) and had the potential to kill more than a hundred people, the report said. The dam was marked for decommissioning.

Vale said in a statement that the report comprised the views of specialist engineers, who are obliged to work within strict procedures in risk identification.

"There is no known report, audit or study with any mention of an imminent risk of collapse at Dam 1 in the Corrego do Feijao mine in Brumadinho," Vale said.

"To the contrary, the dam had all its certificates of safety and stability attested to by local and foreign specialists."

Vale has consistently said the collapsed dam was declared sound by an independent auditor in September.

The audit by Germany-based TUV SUD, which was seen by Reuters, said the dam adhered to the minimum legal requirements for stability but raised a number of concerns, particularly about drainage and monitoring.

The auditor made 17 recommendations to improve the dam's safety. Vale said the recommendations were routine and that the company attended to them all.

It is still not known what was behind the collapse, but a state environmental official said this month that all evidence pointed to liquefaction, a process whereby a solid material such as sand loses strength and behaves like a liquid.

The company has lost a quarter of its market capitalisation -- or nearly US$US19 billion ($A27 billion) -- since the January 25 collapse, Brazil's deadliest mining accident.

Australian Associated Press