Vale Decharacterization Plans for B3/B4 & Superior South Dams
Vale will start activities with unmanned equipment for the removal of tailings from B3/B4 dam at Mar Azul mine in Nova Lima and Sul Superior dam at Gongo Soco mine in Barão de Cocais. Actions were assessed and approved by the Public Prosecutor's technical auditor, in addition to the entire body of external consultants hired by the company to prepare the projects, and represent the progress of the company's Decharacterization Program and the commitment to an approach fully focused on the safety of people and structures. The decharacterization of these dams, which are currently at an emergency level 3 of the Emergency Action Plans for Mining Dams, is a complex process. Aware that any intervention may increase risks, the company has already carried out several preventive actions, including the removal of all residents from the respective Self-Rescue Zones and the construction of back-up damages (downstream containment structures) in both territories.
At the Superior Sul dam, the removal will begin with the collection of samples, which aims to increase knowledge on the characteristics of the material in the reservoir, to improve and the techniques that will be used in the decharacterization process, in addition to subsidizing studies to define vibration control levels. 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. It should be noted that all activities performed and planned for the two dams will be fully executed with unmanned equipment, operated remotely and safely from a control center outside the structures. All actions were communicated to the technical audit of the Public Prosecutor's Office of Minas Gerais and the competent bodies.
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 the nearby communities. In addition, it is also worth considering additional measures to minimize any residual impacts on water bodies downstream of the back-up dams.
The back-up dams built downstream of the two dams are complete and have the capacity to contain the tailings if needed. The structure that serves South Superior dam is 36 meters high and 330 meters long. The structure that serves B3/B4 dam is 33 meters high and 221 meters long. The works follow the strictest Brazilian standards, the best engineering practices and technical references from international entities used for similar constructions. Specialist companies, independent from the designer and the builder, certified and certified that the back-up dams are stable and therefore, provide safety to the downstream communities. The technical auditor of the Public Prosecutor's Office of Minas Gerais also ratified the stability of the back-up dams.