The Mariana dam disaster: rule before remedy

This is article 1 of 2 in The Roman Ledger series.

I. The disaster

At about half past three on the afternoon of 5 November 2015, the Fundão tailings dam in Minas Gerais failed. Some forty million cubic metres of mine waste went down the valley of the Rio Doce. It destroyed the village of Bento Rodrigues, killed nineteen people, and reached the Atlantic roughly six hundred kilometres away. It remains the largest environmental disaster in Brazilian history.

The dam served the Germano iron ore complex, operated by Samarco Mineração SA. Samarco was a joint venture owned in equal shares by Vale SA and BHP Billiton Brasil Ltda. Above BHP Billiton Brasil sat the dual-listed BHP group: BHP Group plc, incorporated and domiciled in England, and BHP Group Ltd, incorporated in Australia.

Neither BHP parent operated the dam. Neither owned it. Samarco did, and Samarco was two corporate levels below them, held through a Brazilian intermediate company and jointly with an unrelated Brazilian mining group. On any orthodox English analysis, that distance is the end of the matter.

It was not.

II. The proceedings

In November 2018 proceedings were issued in England against both BHP parents. The claimant group is the largest in English legal history: more than 720,000 individuals, some 1,600 businesses, seventy-eight churches and faith institutions, forty-six municipalities, seven utility companies, and over 9,500 members of indigenous and Quilombola communities. The claim is valued at approximately £36 billion.

The procedural history was punishing. In November 2020 Turner J struck the claims out as an abuse of process, in terms that left little doubt about his view of them: the claimants' decision to litigate in Brazil and England simultaneously would, if unchecked, foist upon the English courts the largest white elephant in the history of group actions. He added, obiter, that he would in any event have stayed the claims against the English parent under Article 34 of the Brussels Recast Regulation, and those against the Australian parent on forum non conveniens grounds.

The Court of Appeal reversed in July 2022. The Supreme Court refused BHP permission to appeal in 2023. Separate Brazilian settlements with public authorities followed in October 2024, without disposing of the English claims.

The liability trial ran from October 2024 to March 2025. On 14 November 2025 O'Farrell J found both defendants liable. The Court of Appeal refused permission to appeal the liability findings on 6 May 2026. The second-stage trial, on causation and quantum, is listed for October 2026.

III. Why England? Domicile, and the rule that removed the escape

The first question is why an English court heard a Brazilian claim about a Brazilian dam at all.

The answer has nothing to do with environmental law. When the claim was issued, the United Kingdom was bound by the Brussels Recast Regulation. Article 4 provides that persons domiciled in a Member State shall be sued in the courts of that State. BHP Group plc was incorporated and domiciled in England. It could therefore be sued in England as of right.

The decisive point is what Article 4 excludes. In Owusu v Jackson the European Court of Justice held that a court seised on the basis of domicile may not decline jurisdiction on the ground that a court outside the Union would be a more appropriate forum. Forum non conveniens, the doctrine on which an English defendant would ordinarily rely to send a foreign dispute home, was simply unavailable.

That constraint shaped everything that followed. Turner J could not stay the claims against the English parent on forum grounds, because Owusu forbade it. What he could do, and did, was strike them out as an abuse of process, using the court's inherent jurisdiction to achieve something close to the same result. The Court of Appeal held that this went too far.

Jurisdiction over the Australian parent rested on different ground: it was joined as a necessary and proper party under the English service-out gateway, and was therefore subject to the ordinary forum analysis.

So the English forum was the product of a European jurisdiction rule containing no environmental content whatever. It says only where a defendant may be sued.

IV. Why Brazilian law? Rome II and the place of the damage

Jurisdiction determines the court. It does not determine the law that court applies. Those are separate questions, and conflating them is the commonest error made about this case.

Under the Rome II Regulation, the law applicable to a non-contractual obligation arising out of environmental damage is, in the ordinary case, the law of the country in which the damage occurs, with a claimant option in environmental cases to choose instead the law of the place of the event giving rise to it. The damage occurred in Minas Gerais. Brazilian law governed the substance of the claim from beginning to end.

This is the pivot of the whole case. The English court was not applying English standards to BHP. It was applying Brazilian standards, and Brazilian standards are materially more claimant-friendly than anything in English law.

V. What Brazilian law supplied

Federal Law 6.938 of 1981 does two things that English law does not.

First, it defines the person liable in deliberately wide terms. A polluter is any person, natural or legal, of public or private law, directly or indirectly responsible for an activity causing environmental degradation. The category of the indirect polluter has no English analogue.

Second, it makes that liability strict, and joint and several, for damage caused to the environment and to third parties. There is no requirement to establish negligence, no duty-of-care enquiry, and no need to show that this defendant's conduct was the sole or dominant cause.

The question for the court was therefore narrow: were the BHP parents indirect polluters? It held that they were, on a multifactorial assessment of BHP's control over the polluting activity, its degree of involvement in that activity, its financing of it, and the economic benefit it derived from it. Liability was additionally established on a fault basis under the Brazilian Civil Code. The claims were not time-barred.

It is worth pausing on what that test examines. Control, involvement, financing and benefit are not operational matters buried in a subsidiary. They are the ordinary business of a parent board: capital allocation, the appointment of directors to joint-venture boards, approval of expansion, receipt of dividends. The liability found was the company's. The evidence establishing it was the board's.

VI. What English law governed

English law was not absent. It governed procedure, and only procedure.

Rome II excludes evidence and procedure from its scope, while referring rules of prescription and limitation to the applicable law. The judge drew the line precisely. The substantive rules of prescription were Brazilian, by reason of that referral. But whether the claim forms had been validly issued and served so as to stop time running was a question of English procedural law, governed by the Civil Procedure Rules. She held the claims survived on either analysis.

The composite is worth stating in one sentence. A Brazilian statute of 1981 was applied by an English judge to an Anglo-Australian parent company in respect of a dam operated by a joint venture two levels below it, because one European regulation said the defendant had to be sued where it lived and another said which law then applied.

VII. What English law would have done instead

Suppose the damage had occurred in England, so that English substantive law applied. The claim would have looked entirely different, and considerably worse.

There is no indirect polluter. English law has no statutory category capturing a person indirectly responsible for a polluting activity. The Environmental Damage Regulations impose administrative remediation duties on operators and confer no private cause of action. Part IIA of the Environmental Protection Act 1990 works through remediation notices served by regulators. Neither gives a claimant a route to a parent.

Separate legal personality holds. A parent is not liable for its subsidiary's torts by reason of ownership or control. The veil is pierced only in the narrowest circumstances, essentially where a person deliberately frustrates an existing legal obligation by interposing a company. Nothing in the Mariana facts approaches that.

The parent-company duty of care is a duty of the parent's own. Chandler v Cape, Vedanta and Okpabi establish that a parent may owe a duty in negligence to those affected by its subsidiary's operations, but not because it is the parent. The duty arises from what the parent itself did: promulgating group-wide policies and taking active steps to see them implemented, or holding itself out publicly as exercising supervision. This is ordinary negligence, not a special category. It requires the claimant to prove duty, breach, causation and damage.

The contrast with Brazilian law could hardly be sharper. Under Law 6.938, control and benefit are sufficient. Under English law, control and benefit are merely the raw material from which a claimant must construct a duty, and having constructed it must then prove that it was breached and that the breach caused the loss.

Strict liability in English law has been narrowed almost to vanishing. The rule in Rylands v Fletcher looks superficially apt for an escape of impounded material. It is not. Cambridge Water added a requirement that damage of the relevant type be foreseeable; Transco confined the rule to exceptional cases of extraordinary and unusual use, and declined to develop it into a general principle of strict liability for hazardous activity. A tailings dam might qualify. But the rule binds the occupier of the land from which the escape occurred, Samarco, not a parent two levels above.

The honest conclusion is that on English substantive law these claimants would very probably have lost, or never have been funded. What made the case winnable was the applicable law, and the applicable law was Brazilian because the damage was Brazilian.

VIII. What this means for boards

Four consequences follow for directors of English-parented groups, and they should be kept distinct.

No director was a defendant. Mariana is a decision about corporate liability, not personal liability, and any account suggesting otherwise is wrong. But the test applied was built from board-level conduct, and the disclosure exercise in any comparable case will be a disclosure of board papers.

Group policy can be constitutive. On the English authorities, published group-wide standards and public assertions of supervision are among the routes by which a parent assumes a duty it would not otherwise owe. A tailings management standard, a group HSE policy, a transition plan approved by the board: each is capable of supplying the connection on which a duty is founded. Disclosure is not a neutral act.

Internal accountability is weaker than external exposure. A director's duties under sections 172 and 174 of the Companies Act 2006 embrace the impact of the company's operations on the community and the environment. The attempt to enforce those duties by derivative claim in respect of climate management nonetheless failed at the permission stage in ClientEarth v Shell. Members struggle to hold the board to account; foreign claimants may hold the company liable for billions.

The governing law is chosen by the geography of the harm, not by the group. A board cannot select the liability regime to which its overseas operations expose it. Wherever the damage occurs, that jurisdiction's substantive law is likely to travel to whichever forum the claimants can reach.

IX. What Brexit changed, precisely

The European instrument that delivered the English forum in Mariana no longer applies to the United Kingdom.

Brussels Recast is gone, and with it the Owusu prohibition. Jurisdiction over an English-domiciled defendant is once more governed by common law, and forum non conveniens is available: an English parent sued in England may now argue that Brazil, Zambia or Malaysia is the proper place. The United Kingdom's application to accede to the Lugano Convention was refused, and the instruments it has since joined concern the recognition and enforcement of judgments rather than direct jurisdiction. Rome II, by contrast, was retained, so the choice-of-law analysis is unchanged.

It would be an overstatement to say that a case like Mariana could no longer be brought. Limbu v Dyson, the first post-Brexit jurisdiction challenge of this kind to reach the appellate courts, is the corrective. The High Court stayed those claims on forum grounds in 2023. The Court of Appeal reversed in December 2024, emphasising that a defendant sued in its own domicile is sued as of right and that this should not lightly be disturbed, and the Supreme Court refused permission to appeal in May 2025.

The accurate statement is narrower and still significant. Brexit converted a rule into a discretion. Under Owusu no forum argument was available at all. Now there is one; it must be fought; and in Limbu it took three levels of court and some two and a half years to resolve, before anyone reached the merits. Turner J had already indicated he would have stayed Mariana on forum grounds had he been free to. What has been lost is not necessarily the outcome. It is certainty, and years.

X. The question this leaves

Stand back from the detail and the shape of the case is arresting.

The rule that made BHP liable was Brazilian, and forty years old. The rule that produced an English forum was European, and said nothing about the environment. The rule that governed service was English. Not one element of the modern architecture of sustainability regulation, no taxonomy, no reporting standard, no due diligence directive, contributed anything to the outcome. At most such material might have furnished evidence of control or knowledge.

Meanwhile, in the same period, the European Union has been engaged in the most detailed exercise in environmental classification ever attempted, and has twice removed from it the elements that would have attached a person and a remedy to the duties it created.

Why does a system capable of specifying corporate environmental conduct in thousands of prescribed datapoints deliver so little to the people actually harmed, while a single Brazilian provision from 1981 delivers £36 billion?

That question is the subject of the second part of this article, and the answer is older than either.

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