Município de Mariana & Others v BHP Group (UK) Ltd and BHP Group plc & Anor

Extended disclosure must be tailored to the issue and assessed by reference to what is reasonable and proportionate. Model B is appropriate where the relevant information is primarily within a party’s own knowledge or the documents are likely to be common to both parties. Model D may be ordered for a new causation issue where contemporaneous documents may exist independently on each party’s side and the proposed search is limited and proportionate. Model C is appropriate where a disclosure issue is based on a general assertion and a focused request is needed to identify individuals, dates and the basis of the search. Confidential material held by former solicitors may be ordered for disclosure subject to a process addressing consent, redactions and timing.

The judgment determined discrete disclosure issues arising from draft disclosure review documents in Part 20 proceedings concerning the collapse of the Fundão dam. The issues concerned Vale’s market relationship with Samarco, policies governing Vale’s involvement in Samarco, whether earthquakes caused or contributed to the collapse, BHP’s alleged participation in negotiating or performing the TTAC, and documents from related United States security class-action proceedings.

The court had to determine which extended disclosure model—B, C or D—was reasonable and proportionate for each issue, and how disclosure of documents subject to confidentiality obligations should be managed.

1. For disclosure issue 5, model B was ordered for both BHP and Vale. Information concerning Vale’s market activities was within Vale’s knowledge and relevant documents would be held by Vale. Documents concerning Samarco’s policies and guidance were likely to be common to both parties. Requiring model D disclosure would therefore be inappropriate, unreasonable or disproportionate.

2. Model B requires production of key documents relied upon, documents necessary to explain the party’s case and adverse documents. It does not require a search for documents, although a party may conduct a search to support its pleaded case.

3. For disclosure issue 13, model D was ordered. The alleged role of three earthquakes in causing or contributing to the collapse was a new pleaded issue. Contemporaneous internal reports, discussions or findings might exist separately within the parties’ records. The proposed 2015–2016 date range was not an unreasonable burden.

4. For disclosure issue 14, model C was ordered. Vale’s allegation that BHP participated in negotiating or performing the TTAC raised both Brazilian-law and factual issues. Because the factual allegation was insufficiently particularised, Vale was directed to identify relevant individuals, date ranges and the basis of the request, so that the search remained manageable.

5. Documents from the United States security class action were ordered to be disclosed with appropriate safeguards. Vale’s solicitors had to provide a witness statement explaining the confidentiality order, the consent process, steps taken and the estimated timetable. The documents were otherwise to be disclosed in the first tranche by 19 April 2024.