On January 25th of this year, a deadly dam disaster struck Brazil, unleashing a river of mud.
The muddy avalanche buried everything in its path and caught people unaware. The collapse of he Brumadinho Dam has left 120 dead and several hundred are still missing. Heavy rain hindered the search parties, and even though rescue attempts are continuing, the chances for any more survivors are slim.
Dams that you may know of use water to generate hydroelectric power. But Brumadinho dam is different; it is a tailings dam. Tailings dams are used to store the slushy residue from mining. Vale, the biggest mining company in Brazil as well as the largest iron ore company in the world, owns the nearby Feijao mine and claimed responsibility for the disaster. Let's find out more.
What Are Tailings?
Minerals such as copper, gold, and iron exist in nature in the form of ores. Ores are rocks that contain large quantities of the mineral. To extract the mineral, mines use a large amount of water to crush the rock using heavy machinery. The powdered rock with a sand-like texture that gets left behind is referred to as tailings.
What Is A Tailings Dam?
A tailings dam is specifically built to hold in tailing ponds -- water with finely ground rocks. Some of these tailing ponds can be as large as lakes. While the sand settles at the bottom, the water can be recycled and reused in the mining process.
The dams maintain a stable drainage system to prevent the ponds from overflowing. The sediment that drains out forms a beach which buffers the water. Once the sediment builds up to a certain level, the easiest and cheapest way to prevent the dam from overflowing is to build on top of the current dam (see image). But it is not the most stable method. In fact, the Brumadinho Dam was 28 stories high when it fell apart.
As these tailing dams are built next to mines, toxic chemicals that exit the mines often enter the water in the dam. In addition, tailing dams are susceptible to overflowing due to sediment and heavy rainfall. Similar to water-storage dams, these dams are designed based on the contour of the river and specially made to withstand earthquakes and other disasters.
Impact On Environment
Unfortunately, this is not the only dam incident in Brazil. Four years ago, another dam broke apart in Minas Gerais. As both dams were made by the same company, Vale is facing scrutiny for their inability to maintain a stable dam, and have been ordered by the court to stop operation on eight tailings dams.
In addition, the Brazilian government is being criticized for not enforcing stricter policies to ensure the dam’s safety. The Brumadinho Dam had been developing cracks according to some workers who had seen a leak patched last year. The muddy avalanche has polluted the nearby Paraopeba River which is used by locals.
Tailings Dams are not specific to Brazil. All around the world for the past two decades, tailing dams have been collapsing due to failing infrastructures like holes in the wall or damage to pipes. These startling impacts reflect the downsides of these billion-dollar projects.
Nevertheless, these dams are still being built and supported by the government. But as to whether these 3,500 dams will bring even more disasters, only time will tell.
Sources: NPS, VancouverSun, BBC, NYTimes, Internationalrivers.org, PBS