• Vale, the Brazilian mining company responsible for two deadly dam collapses since 2015, has another dam that’s at “imminent risk of rupture,” a government audit warns.
• The Xingu dam at Vale’s Alegria mine in Mariana municipality, Minas Gerais state, has been retired since 1998, but excess water in the mining waste that it’s holding back threatens to liquefy the embankment and spark a potentially disastrous collapse.
• Liquefaction also caused the collapse of a Vale tailings dam in 2019 in Brumadinho municipality, also in Minas Gerais, that killed nearly 300 people; the 2015 collapse of another Vale dam, in Mariana in 2015, caused extensive pollution and is considered Brazil’s worst environmental disaster to date.
• Vale has denied the risk of a collapse at the Xingu dam and says it continues to monitor the structure ahead of its decommissioning; regulators, however, say the company still hasn’t carried out requested measures to improve the structure’s safety, and have ordered an evacuation of the immediate vicinity.

This article originally appeared in Mongabay.
Featured image: Vale’s Xingu mining complex in Mariana. Image by Google.

by Juliana Ennes

A dam holding back mining waste from Brazilian miner Vale is at risk of collapsing, a government audit says. The same company was responsible for two tailings dam collapses since 2015 that unleashed millions of gallons of toxic sludge and killed hundreds of people in Brazil’s southeastern state of Minas Gerais.

The retired Xingu dam at Vale’s Alegria iron ore mine in Mariana — the same municipality where a Vale tailings dam collapsed in November 2015 in what’s considered Brazil’s worst environmental disaster to date — is at “serious and imminent risk of rupture by liquefaction,” according to an audit report from the Minas Gerais state labor department (SRT), cited by government news agency Agência Brasil. The SRT did not immediately reply to Mongabay’s emailed requests for comment; it also did not answer any phone calls.

In the May 20 audit report, only released last week, the SRT said the Xingu dam “does not present stability conditions.” “It is, therefore, an extremely serious situation that puts at risk workers who perform activities, access or remain on the crest, on the downstream slopes, in the flood area and in the area on the tailings upstream of the dam,” the document says.

In a statement, Vale denied the imminent risk, saying the dam “is monitored and inspected daily.” It said the structure’s conditions and safety level remain unchanged, rated level 2 on a three-point scale.

The 2015 collapse of the Fundão tailings dam belonging to Samarco, a joint venture between Vale and Anglo-Australian miner BHP Billiton, killed 19 people in the village of Bento Rodrigues, burying them in toxic mud, and flushing mining waste into rivers that affected 39 municipalities across two states. The mining waste eventually flowed more than 650 kilometers (400 miles) from its source to the Atlantic Ocean.

The district prosecutor’s office in Mariana told Mongabay that the Minas Gerais state prosecutor-general has requested the National Mining Agency (ANM) to assess the real risk of the dam rupture. “Any irregularity in the change in the classification of the structure will be evaluated after the inspection carried out by the ANM and, if necessary, with subsequent investigations,” the district prosecutor’s office said.

The ANM rated the Xingu dam’s safety at level 2 in a September 2020 assessment, after requesting Vale to improve the structure. Vale has fulfilled part of the request, but has sought a deadline extension for other repair works, without major changes in the structure, according to the ANM’s website.

In its most recent inspection, on May 5, ANM identified structural problems where no corrective measures had been implemented, according to its website. By then, the ANM considered the potential environmental impact “relevant” and the socioeconomic impact “medium,” given the concentration of residential, farming and industrial facilities located downstream of the dam.

Vale ceased dumping mining waste in the Xingu dam in 1998, but keeps workers on site to monitor the dam’s stability until it’s fully decommissioned. The decommissioning plans is in place but hasn’t been carried out yet, according to Ronilton Condessa, director of the Mariana mining workers’ union, Metabase. No timeline has been given for the decommissioning; a similar structure, the Doutor dam at Vale’s Timbopeba mine in neighboring Ouro Preto municipality, will take up to nine years.

Last week, Vale announced the suspension of train operations to the Mariana complex where its Alegria mine is located, after an evacuation order from labor auditors. The area in the immediate vicinity of the mine, known as the self-rescue zone, remains evacuated. Work at both the Timbopeba and Alegria mines has been halted.

Condessa said that because the Xingu dam is located inside the mining complex, workers continue to pass by it daily on their way to other mines that are still active.

Vale has scheduled a meeting with workers from the dam for June 16 to explain the current situation, according to Condessa. “The evacuation orders look like a preventive measure, but we still need to see a technical study in order to properly evaluate the risk,” he told Mongabay in a phone interview.

The Minas Gerais state civil defense agency said the evacuation of the self-rescue zone was ordered on a “preventive basis to protect the lives of people living downstream of the dam.”

“In collaboration with the SRT, Vale is taking measures to continue to guarantee the safety of workers, in order to resume activities,” Vale said in a June 4 statement.

A two-and-a-half-hour drive west of the Alegria mine in Mariana is the municipality of Brumadinho. This was the site in 2019 of Brazil’s deadliest mining disaster, when a tailings dam at Vale’s Córrego do Feijão iron ore mine collapsed, killing nearly 300 people. The cause of the dam’s failure was attributed to a process known as liquefaction, in which excess water weakens the dam’s embankment. This is the same risk recently identified at the Xingu dam at Vale’s Alegria mine.