Vale said work using unmanned equipment has commenced on the B3/B4 dam, at Mar Azul mine, in Nova Lima (MG), and Sul Superior dam, at Gongo Soco mine, in Barão de Cocais (MG).
The company said the remediation was "a complex process", involving local government approval, evacuations and the construction of back-up dams.
At the Sul Superior dam, the work will start with a collection of samples to increase knowledge on the characteristics of the material disposed in the reservoir.
Channels will also be opened to improve the flow of water from the structure, preventing accumulation in the reservoir, especially during the rainy season.
At the B3/B4 dam, the tailings removal will be performed together with the completion of the partial removal of a waste pile present at the site, from which 350 thousand cubic meters of material have already been removed since November 2020
"In view of the complexity and risks of the decharacterization process of these structures, Vale informs that it has strict control over all the actions implemented with the objective of ensuring the safety of workers and people living in nearby communities," said the company.
All activities will be fully executed remotely using unmanned equipment from a control centre.
The decharacterization of upstream dams is a legal obligation of all mining companies in Brazil, but is particularly pertinent for Vale in the wake of the Brumadinho dam disaster in January 2019, which claimed 270 lives.
