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The rupture of the Vale dam last Friday (25) may have been caused by liquefaction, a problem that only occurs in systems built upstream by the uplift, as in the Brumadinho (MG) structure, the Undersecretary for Environmental Regulation Secretary of State for the Environment, Hidelbrando Neto.
Decommissioning: Understanding the process announced by Vale
However, it would be necessary to understand why liquefaction would have occurred, said the undersecretary, because the data provided by Vale show this equipment called piezometers n & # 39 did not detect the internal movement of water in the structure.
The conclusion in the Samarco case was published by the authorities and then confirmed by a study subcontracted by the miners themselves, which indicated technical causes of liquefaction but did not report the culprits.
"The two disasters involved upstream dams and in both cases, at least that this is the information we receive here is liquefaction, "said Neto, pointing out that ns another method of building bars
"So I think the Union will walk the path to stop, ban, these dams upstream, what the state did", did he added, pointing out that the government of Minas Gerais had been stopped any license involving any type of dam until the country revises its regulations, in addition to prohibiting the application of the technology in upstream, in a decree of 2016.
The authorities also pointed out that some factors that can sometimes precipitate problems in the dams have not been verified.
"There was no tremor, there was no rain, which are usually triggers." The question everyone asks is: what happened?
The break-up of Vale's dam on Friday killed at least 110 people, 71 of whom were identified and more than 200 missing.
The upstream system costs about half of the other dams, but presents a higher security risk because its walls are built on a waste base rather than an external material or solid soil.
An Alternative to Iron Ore, Residue and Dam – Photo: Alexandre Mauro / G1
This is the downstream method, when walls are built on dry ground, in addition to other technologies, such as dry residue disposal, cavas or piles.
With nearly 12 million cubic meters of iron ore tailings, the structure that served the Córrego do Feijão mine released a mountain of mud that engulfed the company's administrative area and a dining hall with hundreds of employees. the society. It has also reached the communities, inns, forests and rivers of the region.
There are currently 50 dams upstream in Minas Gerais, of which 27 are in operation and 23 are paralyzed, including Brumadinho.
The State Secretary for the Environment and Sustainable Development of Minas Gerais is responsible for issuing licenses for dams in the state.
But Neto pointed out that the competence to inspect the dams is federal and that, through the public statements already presented by the government and the National Mine Agency (ANM), the legislation should be amended.
The changes, he said, should occur mainly on issues related to technical parameters indicating that the dam is stable.
"Because when you take both disasters, and in both cases, you have reports guaranteeing stability, then you have to review some technical parameters," said Neto.
"ANM has already issued a statement in which it says that will reinforce the inspection and start with that of the upstream dams that are without guarantee of stability," he said.
Neto estimates that the regulations around this type of dam became stricter after the disaster of Samarco, without changing the technical parameters of the badessment.
"What happened most recently was a change of direction, the technical badysis remains the same, all the same … The organ was more efficient, but met the same standards and parameters techniques, "he said. The state of Minas Gerais has already ordered to remove them all, but there is a dam upstream in Brazil, so it must act of a federal change. "
Vale recently announced that it has 10 upstream mining dams, all out of business, and announced $ 5 billion in investments to accelerate the dismantling of these structures.
This week, the company stated that 39, in 2016, shortly after the Samarco event, it had determined the decommissioning of the 19 existing dams located upstream of the iron ore in Brazil.
In recent years, all have become inactive and maintained their stability reports issued by specialized and independent companies, according to Vale.
To speed up the process of dismantling dams, the company said that it will have to stop iron ore production in the areas close to the units located in Minas Gerais, with an impact of 40 million tonnes of iron ore, which will be partially offset by the increase in production in other systems. my production of the company.
Understanding the process of decommissioning dams – Photo: Alexandre Mauro / G1
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