Vale’s decision to halt ore exploration operations and to deactivate ten dams that use tailings storage methods similar to the Córrego do Feijão mine, which broke last week in Brumadinho (MG), was classified by the company’s president, Fábio Schvartsman, of “definitive plan” and “drastic”.
The measure envisages, in practice, to retire the upstream dam method – equal to that of Brumadinho, which is considered cheaper and easier to license, but also the least secure. In it, the alterations (that is, the expansion of the containment structure) are made with the reject itself.
Dams are structures that contain tailings from iron ore beneficiation operations, made with the use of water and chemicals. To increase the storage capacity of these structures there are three types of more common methods: in addition to the amount, there is downstream – which uses other materials such as stones and clay to contain the tailings – and center line – which is a mixture of the two methods .
“(Vale’s decision) means that they will only use dams with elevation by the center-line and downstream methods, in addition they will go to delamination and alternative techniques,” says the engineer and professor of the Federal University of Viçosa (UFV ), Eduardo Marques.
However, the measure is not immediate and still depends on environmental licensing. According to Schvartsman, the interruption and deactivation processes are already ready and will be sent for environmental agency licensing in the next 45 days. If approved, they should last from one to three years.
The company’s decision also leaves it immune to new accidents – despite having been authorized to expand the operation in December last year, the Brumadinho dam has not been receiving tailings since 2015 and yet has become the muddy sea that has left hundreds of missing and, until Wednesday afternoon, 99 dead.
The dam shutdown operation needs to be reviewed, monitored and closely monitored, according to experts heard by BBC News Brazil.
Although safer, downstream and centerline methods can have a greater environmental impact at the time of construction, with, for example, larger deforested areas.
For the engineer Rafaela Baldí, the decision of Vale does not necessarily lead to more security.
According to her, prevails “the mistaken understanding that banning one method solves an accident or several.”
Baldí says tailings dams using the upstream method recorded more accidents than those that did the lifting based on the other two methods. But according to the engineer, there is no information on most of the 268 accidents cataloged between 1910 and 2001 – it is unknown, therefore, whether or not these dams were the upstream model.
She cites the International Large Dams Committee’s (ICOLD) survey of 87 accidents at upstream dams, 27 downstream and 11 per center line. There are still 110 cases without information and others counted as water retention.
“The lack of research, information and lessons learned are still the biggest villains in geotechnics,” says Rafaela Baldí.
The engineer claims that all methods are risky if poorly designed, executed and monitored – and can also be safe if well done and enforced. And, according to her, it is better to invest in information production and knowledge about causes of accidents instead of banning one or another method of damming waste.
The process of halting the production and use of dams also represents an economic impact for the company. The operation should cost about R $ 5 billion.
When it discontinues the dams similar to the one it broke in Brumadinho, Vale says it will cut up to 10% of the ore production per year, equivalent to 40 million tons.
At the same time, the decision to change the method of storing tailings can also represent new types of business for Vale.
UFV professor Eduardo Marques recalls that shortly before the dam broke in Brumadinho, Vale had announced the purchase of a Brazilian company that develops new forms of mining, including dry mining – which eliminates the need for dams to contain waste from the beneficiation process using water.
New Steel, a Brazilian startup that uses magnetic separators to benefit the ore, was bought for $ 500 million in a deal announced in December and authorized by the Administrative Council for Economic Defense (Cade).
The company also develops alternative use for tailings – among them, in construction.
What about the other dams?
There is no guarantee, however, that other mining companies that operate using the same dam technique will adopt the same measures as Vale.
Pressure is not lacking. After the Fundão mine dam broke in Mariana three years ago, the Federal Public Prosecutor’s Office in Minas Gerais sent a recommendation to the National Mining Agency, the former National Department of Mineral Production, not to authorize further dams upstream in Brazil, claiming that the technique is insecure.
A concierge was published in an attempt to hinder new ventures, but little was done to deal with dams in operation or already deactivated.
In the Legislative Assembly of Mines, the bill is still standing that proposes to tighten the licensing rules for mining dams.