The catastrophic collapse of the Samarco iron ore tailings dam in Brazil that flooded the small town of Bento Rodrigues with mud last week is a sobering reminder that mineral extraction is a perilous business. At least six people are dead with more than 20 still missing.
The Samarco iron ore mine is a joint-venture between Brazilian mining company Vale and Australian company BHP.
Fresh reports indicate that Brazilian researchers had reported on the risk the Samarco dam collapsing two years ago. BHP has not commented on whether it was aware of the report.
When such disasters happen our first impulse is often try and ascribe culpability. No doubt there must be accountability if any confluence of human errors was involved in this failure.
However, in the rush to blame we must consider the complexity of how such failures might occur.
Ruling out natural causes
Seismic events and excessive rain and wind can be the natural triggers of what might be a chain of human errors in disaster prevention and response.
The US Geological Survey (USGS) did not record any major earthquake in the region at the time and this part of Brazil is not prone to large tremors. Some reports suggested a very small tremor on a scale of 2.6 on the Richter scale but USGS has noted that dam failures can usually not be attributed to any quake below 4.5.
Minas Gerais state in Brazil is known for its rainfall. However there was no abnormal rainfall or major storm system at the immediate time of the event.
Once we rule out direct natural factors the investigation must focus on the human factors which could have led to this disaster.
We also need to consider separately warning systems that could have prevented deaths and injuries.
The current interviews from the survivors suggest that the only warning they got of the tsunami of mud heading their way was the sheer sound of the collapse.
A good emergency response system would automatically trigger warning alarms, mobile text messages and other radio or TV system alerts. Why did that not happen?
The “bowtie method” is often used to analyse both the prevention and the response of such calamitous events.
This method will likely be followed to identify all the possible ways in which this tragedy could have been triggered. A detailed investigation of this kind can take several months.
Last year, The Mount Polley spill in Canada caused a major environmental hazard but thankfully there was no direct loss of human life, although drinking water quality for around 300 people was affected. The investigative panel which was set up following the spill took a year to issue its report.
The panel concluded that the tailings dam collapsed in that case because its engineering plan had neglected a layer of glacial till underneath the dam body. Fortunately there were no human habitations downstream of the spill path.
In Brazil though there were people living beneath the dam. The community residents cannot be blamed for living where they did. The planning process for the mine is the responsibility of the companies and the government collectively.
If there was a preexisting settlement in harm’s way of a tailings dam, what community engagement was undertaken by the company and the government to configure the facility to minimise harm and dislocation? Were adequate resettlement options provided? These are all essential questions which must be answered.
Mining dam disasters on the rise
There is a long history of dam failures and calamitous events from hydropower stations. The worst loss of life in this regard occurred in China when the Banqiao dam collapse in 1975 killed more than 170,000 people.
However, while hydropower dam breaches and deaths have been decreasing in recent years, mining tailings dam breaches have been on the rise. These failures are not just occurring in developing countries.
The US has endured massive failures, including the Church Rock uranium mine spill in 1972 on Navajo indigenous lands and the 2012 spill in Finland which prompted the establishment of a “Network on Responsible Mining.”
In July 2015, the Centre for Science in Public Participation issued a comprehensive report that found 33 of 67 of all serious tailings dam failures in the last 70 years occurred in the 20 years between 1990 and 2009. The International Commission on Large Dams has even had a specialised working group on mining dams for the past several years but clearly more concerted efforts are needed.
The United Nations Environment Program and the mining industry have developed guidelines for disaster preparedness, including comprehensive monitoring.
Up-to-date guidelines published in 2005 include a need to monitor:
the probability of individual events; the probability of simultaneous events (such as an earthquake resulting in rupture of a pipeline); and complications from unique environmental considerations, such as severe terrain, location on a major river, frozen conditions and so on.
Blame for the current disaster will partly depend on whether guidelines such as these have been followed.
There was initially some speculation about whether Vale and BHP would be responsible for the spill since their joint venture Samarco (established 40 years ago) that operated the mine is “a limited-liability company”. Joint venture companies can be a risk management mechanism but as the Wall Street Journal recently noted, current regulations will not protect BHP and Vale from responsibility.
The research process to investigate the spill has begun by independent experts, including the American Geophysical Union which has set up an online blog to consider causality.
At the end of the day companies like BHP and Vale should approach this matter with humility. If there is blame to be ascribed they should accept and learn from any lapses.
Broader questions of why best practice guidelines and voluntary industry covenants are not adequate to prevent such massive failures must also be asked. Most mining companies remain profitable despite a decline in the level of profits during industry downturns and yet social and environmental performance budgets are often the first to be cut.
Whether or not culpability in such disasters is assumed, companies and governments should take the moral high ground and assume responsibility for ensuring such calamities become far less likely to repeated.