Photo: Ricardo Teles

1. Raising Method

Process of raising the height of the dam to increase its storage capacity. It can be done by the upstream, downstream, centerline, or single-stage method.

Downstream

The construction of the embankments is done in the opposite direction to the dam reservoir, that is, in the direction where the water or tailings flow after passing through the dam.

Upstream

The embankments of the raising are supported on the tailings or sediment previously deposited. Construction is done towards the dam reservoir.

Centerline

Maintains the axis of the dam aligned with the center of the original structure.

Single Stage

Construction of the dam at its final height from the beginning, without subsequent raising.

2. Dam or Dike

Structure built for the disposal of tailings, containment of sediments, or water storage, resulting from the mining process. Dams that store tailings can be called Tailings Storage Facilities (TSFs).

3. Declaration of Stability Condition (DCE)

Technical document that certifies the stability of the dam.

4. De-characterization

The process of De-characterization and transforming a dam so that it no longer receives tailings and/or sediments from its primary activity. At the end of the process, the structure ceases to have the characteristics or function of a dam.

5. Engineer of Record (EoR)

External professional responsible for continuously monitoring and interpreting data from inspection and monitoring activities throughout the entire life cycle of the structures.

6. Downstream Containment Structure (DSR)

A structure built downstream of a dam with the objective of retaining materials from possible ruptures or operational failures, ensuring the protection of lives.

7. Independent Tailings Review Board (ITRB)

An independent group composed of a multidisciplinary team of experienced, internationally recognized experts, appointed to provide opinions and recommendations to Vale regarding the structures.

8. Emergency Level

Convention used in Brazil by the National Mining Agency (ANM) to grade potential emergency situations that could compromise dam safety. The classification can be 1, 2, or 3, with the latter being the most critical.

9. Emergency Action Plan for Mining Dams (PAEBM)

Document that defines procedures and responsibilities in case of emergency.

10. Tailings

Materials resulting from ore beneficiation, generally composed of fine particles and water. Tailings can be reused in the future in some cases.

11. Sediments

These are the solid materials transported and deposited by the action of water or other natural agents. It is necessary to contain these materials, for example, in dam or dike structures, to avoid environmental and operational impacts.

12. Operational Status

Phases of the life cycle of a geotechnical structure: Design, Construction, Operation, Inactive, De-characterization work in progress, and De-characterization.

13. Self-Rescue Zone (ZAS)

Area near the dam where there is not enough time for intervention by the authorities.

14. Secondary Safety Zone (ZSS)

Area furthest from the dam, where there is time for action by the authorities and execution of evacuation plans in case of emergency.

Q&A

What is the difference between de-characterization and decommissioning?

De-characterization is the act of intervening in the structure with the objective of making it completely lose its characteristics as a dam. At the end of the works, the structure remains completely stable and is reintegrated into its relevance and the environment. Decommissioning, on the other hand, is an initial stage of the de-characterization process, which begins with the confirmation that the dam is no longer necessary in the operational context of the project and, therefore, can be deactivated or de-characterized.

With the de-characterization of upstream dams, what will be the destination of the tailings from these structures?

The tailings will be disposed of in exhaust pits and in waste and tailings stacks.

Do these works pose a greater risk to the stability of the structures?

Vale has been adopting all possible measures to increase safety and minimize the risks arising from interventions related to the de-characterization process. In the case of dam de-characterization works, for example, alternatives are being studied such as the use of unmanned equipment (tractors, excavators, trucks, among other types of equipment) with remote operation, helicopters and cargo cable cars for access to risk areas. The goal is to avoid placing people in risk areas.

Not all tailings will be removed from the structures. Even so, can we say that the structures have been de-characterization and are safe for those who live or work in these locations?

It is important to emphasize that the de-characterization project aims to make the structure completely lose its dam characteristics. In other words, at the end of the works, the structures will be fully beneficial and reintegrated into their relevance and the environment. In some cases, residual tailings may remain, which do not compromise the stability of the terrain where the dam was located.

Does Vale share information about work with the community?

Yes. We regularly share announcements about the status of the work and new actions that will be initiated and measures to mitigate and reduce impacts on people. There is also, for dams under construction with evacuated communities, a schedule of meetings and site visits, agreed upon with community representatives and the Public Ministry Office of Minas Gerais.

When did the current program for the elimination of upstream structures begin?

The elimination of dams built upstream (over tailings or sediments) is a commitment reinforced by Vale since the Brumadinho dam collapse in 2019, in addition to being a legal obligation. The collapse led to a change in the company's dam management to ensure greater safety for its structures and communities, and the De-characterization Program is one of the main milestones of this management, with the objective of ensuring that nothing seems to happen again. The first structure eliminated was dam 8B (Águas Claras Mine, in Nova Lima-MG), in December 2019.

Why is it important to eliminate upstream structures?

It is important to increase the safety of communities living near these structures and our operations. When a structure loses its function of retaining water, tailings, or sediments, it no longer presents a risk of accidents like the one that occurred in 2019 at the B1 dam of the Córrego do Feijão mine in Brumadinho.

During the de-characterization process, did the communities in the Self-Rescue Zones (ZAS) remain outside their localities?

The communities located in the ZAS remained outside their homes until the work was completed. When there is no longer a risk of dam failure, people can return if they wish.

Is there environmental licensing for the de-characterization projects?

Since the works are emergency measures, the projects can be started immediately, as provided for by law, with subsequent environmental regularization. The documents related to environmental regularization and respective studies are delivered to the environmental agency.

Will the areas where dams are removed be able to receive physical facilities such as buildings and roads in the future, or will there always be restrictions on their use?

In some cases, it is possible. But we emphasize that the future use of the areas is a process that will take place as discussions progress between the company, society, and the Public Authorities.

How long does each dam de-characterization or removal take? Why does it take so long?

The de-characterization or removal of an upstream structure is a complex process and can take a long time to complete so that it is carried out with due care for safety. Each project has its own characteristics and challenges, and all are based on the premise of the safety of people and the environment. All actions are monitored and receive support from external consultants, authorities, and technical auditors from the authorities.

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