Samarco dam disaster: mining sector must learn from failings

The chain of events and triggers that can cause a disaster like Samarco’s dam collapse is bound to happen again.

The scene of devastation after a dam burst in the village of Bento Rodrigues, Brazil, last year. Picture: AFP

Minas Gerais state police took four months to determine the cause of last November’s deadly collapse of the Fundao tailings dam at the BHP Billiton and Vale jointly owned Samarco iron ore operation.

And they were just as quick to point the finger, seeking qualified homicide (manslaughter) charges against six Samarco executives and one contractor in the wake of the collapse that killed 14 mine workers and five residents.

The police investigation concluded that the cause of the Fundao dam collapse was liquefaction (when solid material turns liquid), with seven contributing factors.

They included alleged failures in water-level monitoring, monitoring equipment failures, and substantial increases in the dam’s height. Yesterday the panel of independent experts assembled by BHP, Vale, and Samarco to identify the cause of the dam failure released their report, some six months after the state police had their say.

Unlike the police report, the panel’s report was not an attempt at attributing blame. It too found that the dam failed because of a liquefaction event.

In doing so, it listed a series of shortcomings and incidents at the dam stretching back to 2009 that the average reader would digest with a sense of rising alarm. But again, it was not in the panel’s remit to apportion blame.

As owners but not operators of the 50-50 Samarco joint venture, BHP and Vale weren’t playing the blame game either.

After all, there are a number of civil, criminal and regulatory investigations — and court actions — under way in Brazil.

So apart from a highly technical but perfectly understandable explanation of what went wrong from the panel, has the exercise of commissioning the 10-month study by the panel of experts been worthwhile? It would be nice to think so. BHP and Vale are sharing the learnings with the world of mining where more than 3500 tailings dams can be found.

But that is no guarantee that there won’t be further dam collapses around the world. The report itself references both recent and decades-old failings at other dams that were severe enough in themselves to have put the global industry on perpetual high alert over tailings dams.

But as the mining goes on, and more and more tailings are added to dams, the long chain of events and unforeseen triggers that can cause the sort of disaster witnessed in Brazil on November 5 last year is bound to happen again.

Mitigation is the only hope. And that means that tailings dams should not be built upstream from population centres. The environment would still get hit but human casualties would be contained. In the case of the Fundao collapse, the nearby village of Bento Rodrigues was all but wiped off the map when 32 million cubic metres of red sludge hurtled down the valley floor below at a speed approaching 40km an hour, eventually making its way 600km across two states and into the ­Atlantic. There are both operating and decommissioned tailings dams all over the world, many of which sit perched above villages and towns. Australia’s relatively flat terrain means it is not such a big issue here.

But you’ve got to wonder about some of those old NSW coal towns. As it is, BHP has done an audit of its 10 biggest tailings dams, including coal in Queensland and NSW, and nickel and iron ore in Western Australia, and Olympic Dam in South Australia.

They have been declared OK.

But as its man in charge of the Samarco response, former Wollongong boy Dean Dalla Valle said yesterday, there was no reason to believe anyone at BHP had any information that indicated that the Fundao dam was in danger of collapsing.

So the world’s biggest miner, with its nominees on the Samarco board, did not see the Fundao collapse coming.

That’s kind of depressing remembering there are 3500 tailings dams out there. But Dalla Valle did offer some hope.

“When you have a significant event like this then you need to use it to always continue to improve, to get better, and I think we’re doing that,’’ he said.

Hopefully the rest of the industry and host governments around the world will follow suit.