backIn the largest mass tort claim in English legal history, the High Court has found in favour of over 600,000 claimants adversely affected by the collapse of the Mariana dam in Brazil.
In November 2015, the Fundão Dam collapsed, releasing around 40 million cubic metres of liquefied iron ore tailings. 19 people were killed and there was catastrophic environmental and property damage affecting large areas of southeastern Brazil.
Claims were brought in the English courts under Brazilian law against BHP Billiton and others by individuals, businesses and municipalities that were affected by the disaster. The total value of the claims is estimated to be in excess of £30 billion.
In 2020, the claims were struck out by the High Court on the basis that Brazil was the more appropriate forum. However, in 2022, the Court of Appeal overruled the High Court, confirming that the claimants had a legitimate interest in suing BHP in England and that the practical realities of pursuing the claim in Brazil would stifle access to justice.
Following a 12-week trial in the Technology and Construction Court, on 14 November 2025 Mrs Justice O’Farrell handed down judgment on the merits, finding in favour of the claimants.
The Judgment
Key issues in the judgment included foreseeability of risk and strict liability under Brazilian law. The court ruled that:
- The dam’s collapse was driven by a range of foreseeable factors, including the liquification of saturated and contractive mining residue as a result of inadequate drainage, lack of stability and continued mining activity.
- Although not the direct legal owner of the dam, by their control and operation of the relevant joint venture, BHP were directly or indirectly responsible for the polluting activity. As a polluter, BHP are strictly liable under Brazil’s Environmental Law for damage caused to the environment and to third parties by the collapse of the dam.
- BHP was liable by reason of fault pursuant to Article 186 of the Brazilian Civil Code, a finding which follows from the degree of control which BHP assumed and exercised over the joint venture’s activity. Despite the dam showing “serious signs of distress” in August 2014, BHP took no action and allowed continued activity.
Practical implications
There will now be a separate trial to determine quantum, with potentially very significant financial consequences for all of the involved parties.
The wider significance of the judgment lies not so much in the Court’s findings on breaches of Brazilian law, but in what it shows about mass tort claims in England more generally. It demonstrates that the English courts are willing and able to hear extra-territorial tort claims on a colossal, and previously unseen, scale. This will give confidence to claimant lawyers and their funders, and may increase the volume of similar claims brought in London against UK domiciled or listed multinationals, including in relation to their overseas operations.