Dam De-characterization

Dam De-characterization

Dam De-characterization

Descaracterização de Barragens

Vale spares no efforts to improve its safety procedures and has taken decisive actions to renew its pact with society. On this page, you will find a compilation of actions and initiatives focused on dam de-characterization, containment, and reinforcement works. These works are key to improving the management of our operations.

According to Brazil’s National Mining Agency, de-characterization is the process to reincorporate a dam – which does not serve its primary purpose of retaining tailings from mining activities – into the relief.

This work may seem simple but it is not. Imagine that each dam has its own identity, like a fingerprint.

Before any de-characterization activity, a company must prepare a thorough and in-depth study to understand the local conditions and specificities of the dam and, then, plan the best alternative for the de-characterization process.

To ensure these specificities are covered, Vale is adopting several de-characterization models.

Click on the boxes to learn more about two of these processes:

Model 1

The infographic below depicts the dam de-characterization process in Model 1.

Hover over the illustrations to get a clear picture of each phase of the process.Hover over the illustrations to get a clear picture of each phase of the process.

Phase 1

Improving the Factor of Safety

It is achieved by pumping surface water and building peripheral channels. The pumping process of some dams involves drilling and operation of deep wells.

Reinforcement

In some cases, the company will consider reinforcing the dam shell to stabilize the structure and ensure future interventions will be carried out safely.

Phase 2

De-Characterization

Once the structure has stabilized, it is de-characterized through the reshaping of the terrain and partially or totally removing tailings from the reservoir. Depending on the structure, revegetation is carried out to reintegrate the area into the local environment.

Phase 3

Monitoring and Control

The last part of the process involves monitoring and controlling the environmental recovery of the area after de-characterization is complete. This phase also includes monitoring the biological stability of the region, that is, assessing the environmental impact of these changes.

Model 2

For the dam in Model 2, Vale decided to begin the process by removing dry (waterless) tailings from the structure. Here is the process:

Hover over the illustrations to get a clear picture of each phase of the process. Hover over the illustrations to get a clear picture of each phase of the process.

Phase 1

Removal of Tailings

First, the tailings are removed from the structure. In some cases, the company uses remotely operated excavators and tractors to prioritize safety. Unmanned trucks also transport the material to an area outside the risk area. Pumping systems and dredgers are also considered in this tailings removal process. The dam shell is removed.

Phase 2

Recovery

After the tailings and the dam shell are removed, the environmental recovery plan will be implemented to reintegrate the area into the local environment.

Phase 3

Monitoring

Monitoring devices are installed.

The de-characterization processes enable reforestation and reintegration of the area into the local environment.

Gallery

See videos and photos of the de-characterization works already started by Vale.

8B Dam

Located at Águas Claras mine, in Nova Lima, 8B no longer serves as a dam since November 2019.

Forquilha I Dam

Peripheral channels have been built to lower the water level at Forquilha I dam, at Fábrica mine, in Outro Preto.

Vargem Grande Dam

Peripheral channels have been built to lower Vargem Grande dam, in Nova Lima.

8B Dam

Details of the de-characterization works at 8B dam in 2019. The structure no longer serves as a dam.

Itabira

Rio Peixe dike construction site in Itabira.

Containment Works

To improve the safety of communities and the environment, in addition to the de-characterization processes, we are carrying out several emergency containment works to subsequently de-characterize some of the upstream dams with a high degree of risk.

Containment structures retain tailings in an extreme scenario of dam breach.

These structures are usually built with concrete, stones or metals, depending on the geological characteristics of the region.

Dams equipped with containment structures for increased safety:

  • Sul Superior dam (Gongo Soco mine);
  • B3/B4 dam (Mar Azul mine);
  • Forquilha l, ll, II and Grupo dams (Fábrica mine).


Current status of the de-characterization:

Completed: dam 8B, at the Águas Claras Mine, in Nova Lima;

De-characterization works started: Rio do Peixe, in Itabira, and construction of the spillway (first de-characterization stage) of the Doutor dam, in Ouro Preto;

Containment works in progress: Dam B3/B4, of Mina Mar Azul, in Nova Lima; and for the Forquilhas I, II and III and Grupo da Mina Fábrica dams, between Ouro Preto and Itabirito;

Containment works completed *: Barragem Sul Superior, in Barão de Cocais.

* Additional recommendations by the auditor of the Public Ministry-MG are in the technical phase.

Preparatory works and actions for de-characterization: Dike 2, Pontal System, in Itabira; Fernandinho Dam and Vargem Grande Dam, in Nova Lima; Sul Superior Dam, in Barão de Cocais.

B3/B4 Dam Containment

B3/B4 dam containment works are underway to protect Rio das Velhas and the Water Treatment Plant in Bela Fama.

B3/B4 Dam Containment

B3/B4 dam containment works are underway to protect Rio das Velhas and the Water Treatment Plant in Bela Fama.

Sul Superior Dam Containment

Containment structure in Barão de Cocais (Minas Gerais) is expected to retain 100% of the tailings from Sul Superior dam in case of an emergency involving breach.

Sul Superior Dam Containment

Containment structure in Barão de Cocais (Minas Gerais) is expected to retain 100% of the tailings from Sul Superior dam in case of an emergency involving breach.

Fábrica Mine Dam Containment

It is being implemented between the cities of Itabirito and Ouro Preto, in Minas Gerais. It was designed to retain the tailings from the dams at Fábrica mine in the event of a breach.

Fábrica Mine Dam Containment

It is being implemented between the cities of Itabirito and Ouro Preto, in Minas Gerais. It was designed to retain the tailings from the dams at Fábrica mine in the event of a breach.

Vale monitors its dams 24/7 through the Geotechnical Monitoring Center, which ensures that these construction phases are implemented safely both for the communities and everyone involved in the construction works.

This monitoring center is equipped with cameras, a robotic station (capable of detecting millimetric movements in the structure) and automated piezometers – a device that measures water temperature, pressure, and volume –, and there is a team of professionals on standby to ensure informed, fast, and safe decisions are taken.

Workers carrying out activities directly in the dams are trained on the Emergency Action Plan for Mining Dams (PAEBM, Plano de Ação de Emergência para Barragens de Mineração) and have immediate rescue support in case of emergency.

We know that construction works on the dams can affect the surrounding communities. So, we take several measures on a regular basis to mitigate the effects:

Water trucks spray the access routes to avoid the dispersion of dust from the construction works;

Noise meters are installed at the construction sites to control the noise limit;

A telemetry system monitoring the speed of trucks carrying supplies for the construction works is installed to improve traffic safety;

Safety signs are installed on access routes and roads near the construction works;

All vehicles used in the construction works are visually inspected to ensure adequate traffic conditions;

The company is raising awareness among drivers through educational campaigns, inspections, and breathalyzer testing;

Alternative access routes to the construction sites have been created to reduce heavy vehicle traffic on the roads used by communities.

Do you have any questions about the terms used on the page?

Check out our Glossary learn more about technical and specific terms for dams.

Click and Check out

Since the beginning of the pandemic, we have taken several measures to reinforce the health and safety of all our direct and third-party employees and foster a safe work environment.

  • Screening with daily checklist and body temperature measurement is mandatory for all employees before the beginning of the workday;
  • At the construction sites, the company provides alcohol-based hand sanitizer and guidance on how to prevent COVID-19;
  • Intensified cleaning of facilities, tools, and equipment before each work shift;
  • Distribution of masks for employees at all the construction sites;
  • Mass testing of direct and third-party employees.
Learn more about the measures taken by Vale to prevent the spread of the coronavirus. Click here.

Frequently Asked Questions

What is the difference between de-characterization and decommissioning?

De-characterization is the process by which a dam no longer serves its primary purpose of retaining tailings. After the construction works are completed, the remaining structure is fully stable and reincorporated into the relief and the environment.

Decommissioning is the initial phase of the de-characterization process, which begins upon the confirmation that such dam is no longer required in the operational context of the project and, therefore, can be deactivated or de-characterized.

How will the tailings from these upstream dams be handled after de-characterization?

The tailings will be disposed of in depleted mines as well as in tailings and waste rock piles.

Can these construction works further affect the stability of the structures?

Vale has been adopting all measures required to increase safety and mitigate the risks from interventions related to the de-characterization process. In the case of dam de-characterization works, the company is considering alternatives, such as using unmanned/remotely-operated equipment (tractors, excavators, and trucks, among others), in addition to helicopter and cargo cable car to access risk areas. The goal is to keep people away from the risk area.

Not all tailings will be removed from the structures. Still, is it possible to state that the structures have been de-characterized and are safe for those who live or work in these locations?

It is important to emphasize that the purpose of the de-characterization project is to fully de-characterize a dam from its purpose of retaining tailings. That is, once the de-characterization works are completed, the structures are fully stable and reincorporated into the relief and the environment. In some cases, there will be residual tailings that will not affect the stability of the soil in which the dam was built.