Brazil dam in critical alert

Article by Amanda Jasi

Leo Correa/AP/Shutterstock
Emerson dos Santos stands on the debris of his mother's house following the collapse of Dam 1 in Brumadinho, Brazil. Rescuers in helicopters on Saturday searched for survivors while firefighters dug through mud

ON 22 March Vale raised the alert level of its Sul Superior Dam of the Gongo Soco mine located in Barão de Cocais, Minas Gerais, Brazil to level 3, the highest grade of alert, reports The Guardian. According to The Guardian, Brazil’s Mining and Energy Secretary said that a level three alert means "a rupture is imminent or already happening".

This alert comes two months after the fatal collapse of another Vale mine tailings dam located in Brumadinho, Minas Gerais, Brazil. Mine tailings dams are used to store mine tailings, the waste product of ore extraction and processing. Dam 1 of the Córrego do Feijão mine collapsed on 25 January. Since then 212 people have been confirmed dead and 93 people are missing.

An independent auditor informed Vale that Sul Superior was at imminent risk of rupture on 20 March, and on 22 March Vale initiated level 3 of the Mining Dams Emergency Action Plan (PAEBM).  The Sul Superior dam is part of Vale’s accelerated decommission project and residents of the dam’s Self-Rescue Zone (ZAS) a total of 442 people  had already been evacuated on 8 February as a preventive measure. The ZAS (previously referred to as the Self-Saving Zone) is the area 10 km downstream of the dam, or “the equivalent to the arrival of the flood wave in 30 minutes”. In this area, Vale is responsible for alerting the population, in the event of an emergency.

Flavio Godinho, Lieutenant Colonel of the Minas Gerais Civil Defence Department, said that “any activity at the dam could trigger a rupture,” reports The Guardian. He also said that the authorities are studying the Sul Superior dam to review its existing contingency plan.

Public authorities are working to identify and guide residents of the dam’s Secondary Self-Rescue Zone (ZSS), the area in the flooding map that is not within the ZAS. Approximately 6,000 people are residents of the ZSS for the Sul-Superior dam. Vale has adopted measures to support an evacuation drill in the ZSS in Barão de Cocais, which will occur at 16:00 local time on 25 March.

Marcelo Klein, Coordinator of Vale's Immediate Response Committee, said: “In a crisis management situation, it is important that people stay calm, alert, and attentive to all the instructions provided. Please, trust and rest assured that the public authorities have a huge and very qualified team working behind the scenes and thinking of every detail to ensure the safety and well-being of everyone at the Secondary Safety Zone”

The Sul Superior dam was built using the upstream method, which Deputy Director of the University College London Hazards Centre Stephen Edwards referred to as “the worst type”. Dam 1 was an upstream dam, and so was a Samarco mine which fatally collapsed in 2015. Samarco is a joint-venture of Vale and BHP Billiton. Recently, Brazil banned upstream dams.

Vale reiterated that it “continues to adopt a series of preventive measures to increase the safety condition” of its dams.

The Paraopeba river

The Paraopeba river is located near the site of Dam 1 which collapsed in January. Since the collapse Vale has been monitoring the river. The company has 65 monitoring points above the Dam 1 breach site.

In the two months since the collapse, 300,000 analyses have been conducted using water, soil, tailings and sediment collected from the river. The analyses were conducted by four specialised labs hired by Vale. Vale says that the analyses show that the river is recoverable, though environmental recovery depends upon a set of actions, “including the containment of solid tailings currently occupying the site where Vale's facilities were once located”. Vale is developing a recovery plan for the river in collaboration with other companies, institutions and environmental agencies.

To accelerate the recovery of the Paraopeba river, Vale is working to contain the mine tailings from Dam 1. The company is currently negotiating with environmental agencies on a plan to prevent tailings from flowing into the river. The plan includes “the construction of four large structures – a dike, two hydraulic barriers and a sheet pile retaining wall – in the basin of the Ferro do Carvão stream, a tributary of the Paraopeba river”. The stream received the highest discharge of material from Dam 1.

The company is also building a water treatment plant 500 m from the confluence of the Paraopeba river and the Ferro Carvão stream. It is to have a flow of 2,000 m³/h.

Since the collapse of Dam 1 Vale has distributed more than 37m L of water to 19 municipalities along the Paraopeba river basin for human consumption and livestock and irrigation. The company is currently studying how to strengthen the water supply system in this region as a preventive measure in case of water shortages in the next drought period.

By the first half of 2020 Vale intends to build a 50 km pipeline that will supply Pará de Minas, the city which relied upon the Paraopeba river, with water from the Pará river. The Pará river was unaffected by sediments from the collapse of Dam 1. The intended pipeline is expected to have a flow of 284 L, which is the same amount that the city collected from the Paraopeba river before the dam collapsed. Once the river has been recovered the city’s water supply will be doubled.

Caroline Gleuza, Executive Manager of Environmental Management at Vale, said: “We deeply regret what happened, and we will do whatever it takes to recover the Paraopeba river basin, because we know that it is possible.”

Contamination of rivers by mining waste containing high levels of iron ore and other metals is a matter of great concern, The Guardian reports. It can reportedly last years or decades.

The newspaper says that the Brazilian environmental group SOS Mata Atlântica has claimed to have proof that contamination from the dam collapse has reached the São Francisco river, which supplies hundreds of municipalities and larger cities with drinking water. However, Brazil’s National Water Agency denied further contamination of São Francisco river.

Vale updates

On 21 March Vale received Provisional Operational Authorization from the Secretary of State for Environment and Sustainable Development (SEMAD) for its Laranjeiras dam. The company had been waiting for this after a court decision authorised it to begin activity at the dam again.  The company will now be able to restart operations at its Brucutu dam. The company said on 21 March that it intended to do so “in the next 72 hours”.  

Vale has now outlined a schedule for registration for emergency compensation payments to residents in locations in Brumadinho. Previously the company announced payments to two communities which were most affected by the collapse, Parque do Cachoeira and Córrego do Feijão. Once registrations have been reviewed and accepted, Vale will make payments retrospectively for 12 months, January to December.

Vale has shared the composition of its three Extraordinary Independent Consulting Committees. Two were created in January; one to follow up on the measures for support and recovery following the collapse of Dam 1, the other to investigate the cause of the collapse and find those responsible. In February the company announced a committee for dam safety which is responsible for advising the company’s Board regarding issues of tailings dam safety.

Vale recently informed on its humanitarian aid and recovery actions following the collapse, up until 21 March.

Article by Amanda Jasi

Staff reporter, The Chemical Engineer

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