Vale completes emergency containment works to reduce sediment flow in Brumadinho.

BRAZIL: Three large containment structures (two hydraulic filtration barriers and a dike) and 25 small stabilizing barriers have been installed between B1 at the Córrego do Feijão mine and the confluence of the Ferro-Carvão stream and the Paraopeba river in Brumadinho. This set of actions is part of the Tailings Containment Plan presented by the company to public authorities, shortly after the dam breach.

Vale completed the emergency containment works in Brumadinho (Minas Gerais) announced in June this year. The company has built a number of integrated structures designed to reduce the flow of sediments into the Paraopeba river, thus significantly reducing water turbidity. After the first rains that poured heavily in October, November and early December, the results achieved so far have been considered positive. The structures met the conceptual and fundamental goal of reducing the flow of sediments into the river in the beginning of the rainy season.
Emergency interventions also include removal and proper disposal of tailings upon approval of the Military Fire Brigade of Minas Gerais, and recovery of the affected stretch of the Paraopeba river.
Three large containment structures (two hydraulic filtration barriers and a dike) and 25 small stabilizing barriers have been installed between B1 at the Córrego do Feijão mine and the confluence of the Ferro-Carvão stream and the Paraopeba river in Brumadinho. This set of actions is part of the Tailings Containment Plan presented by the company to public authorities, shortly after the dam breach.
In addition to these structures, a metal pile barrier was installed near the confluence of the Ferro-Carvão stream and the Paraopeba river. This measure allowed cleaning of the river stretch concentrating most sediments. Also, since May 27, the solid flow into Paraopeba river was stopped.
It is important to clarify that all containment structures have been sized to dissipate the energy and speed of water, allowing it to flow through while retaining sediments. Thus, this is an integrated set of works that reduce the water ability to carry solid materials into the Paraopeba river. Water overflow in these structures is expected and monitored according to several parameters, including turbidity.
Vale also set up a River Water Treatment Plant (ETAF) near the confluence of the Ferro-Carvão stream and the Paraopeba river. From May 9 – when it began operating – until the beginning of December, ETAF Iracema returned to Paraopeba approximately three billion liters of clean water, with turbidity levels below 100 NTUs (therefore, within the legal standards established by the National Council for the Environment (Conama), with the removal of heavy metals, iron and manganese mainly.
In mid-May, Vale began preparatory activities to dredge the tailings of an affected stretch of the Paraopeba river, and started dredging in August, after the Firefighters ended the search for victims in this area. This action enables removal of the tailings accumulated in the silted region of the river, clearing its channel to accommodate a higher volume of water in the rainy season.
The material removed during dredging is stored and dehydrated in large geotextile bags. The water drained in these bags is pumped into a treatment plant and returns clean to the Paraopeba, within the standards set out by Conama. Dredging activities are planned to continue until 2020, beginning at the confluence of the Ferro-Carvão stream and the Paraopeba river, and extending almost 2km downstream. To date, about 38,000 cubic meters of material have been removed in this stretch alone.
This set of works mobilized 45 companies, 584 equipment and 2,800 workers, of which at least half are residents of Brumadinho and region. Investments this year alone amount from R$ 400 million to R$ 500 million and are expected to reach R$ 1.8 billion by 2023.
All structures can be decommissioned; that is, they can be disassembled from the moment they are no longer required for stabilization of the affected areas.
Vale clarifies that the emergency containment works have been completed; however, search efforts by the fire service, tailings removal and handling activities, and the environmental recovery of the affected areas continue.

Structural Efficiency Monitoring Plan

Vale implemented the Structural Efficiency Monitoring Plan to ensure the efficiency of the structures built. Monitoring actions are performed 24/7 while data such as rainfall, water turbidity and watercourse flow is monitored online and reported to the relevant agencies daily.
Data from measurements carried out so far showed that in November the volume of rainfall in the region of the Córrego do Feijão mine reached 209.9 mm, with only two days of water outflowing in the metal pile barrier, which is the last containment structure. The water outflowing in these two days registered an average turbidity of 20 NTU, well below the limit of 100 NTUs established by Conama, before even undergoing treatment at ETAF Iracema.
The structures that are part of the Tailings Containment Plan were designed to operate in conjunction and scaled for filtering and overflow purposes. This means that each structure allows the water to flow, but significantly reduces the flow of solids, water turbidity and the flow of sediments into the Paraopeba river.

Remaining structures in the Córrego do Feijão mine

Vale also implemented integrated measures to ensure the geotechnical safety of the remaining structures of the Córrego do Feijão mine. In B1, Vale carried out a geotechnical investigation of the remaining material, in addition to geotechnical boring, which pointed out the necessary measures to complete the stabilization of the remaining material. Partial deviation of rain water contributions and drainage of natural thalwegs (paths of a rainwater course) were carried out upstream the dam. This action will prevent rain waters from carrying sediments into the Ferro-Carvão stream.
In B6, measures included cleaning of the drain at the foot of the dam, restructuring of the surface drainage, water drainage, among others. The dam’s emergency plan has been submitted to the relevant agencies.
The works are monitored weekly by an independent technical audit commissioned by the Prosecution Office of Minas Gerais (MPMG). During the activities, Vale and the contracted companies followed a strict safety protocol prioritizing the safety of workers and the protection of the environment. In addition, all of these structures are monitored 24/7.

Careful removal and proper disposal of tailings

Since the breach of B1 dam, Vale and the Fire Service have been working together in the planning and implementation of tailings removal activities. To date, Vale has removed 1.3 million cubic meters of tailings, which, after being inspected and released for final disposal by the company, are being placed in areas within the Córrego do Feijão mine, previously authorized by the relevant agencies.
To handle the tailings, Vale built an access road where the old railway branch of the Córrego do Feijão mine used to operat e. The new road is open since August 13 and has significantly reduced traffic of heavy vehicles on local roads, in addition to improving safety for communities.
All these measures have been duly reported to environmental agencies and Brazil’s National Mining Agency (ANM) and are systematically reported to these entities. The Fire Department is also up-to-date with the entire process.
To handle the tailings, Vale built an access road where the old railway branch of the Córrego do Feijão mine used to operat e. The new road is open since August 13 and has significantly reduced traffic of heavy vehicles on local roads, in addition to improving safety for communities.
All these measures have been duly reported to environmental agencies and Brazil’s National Mining Agency (ANM) and are systematically reported to these entities. The Fire Department is also up-to-date with the entire process.