The Fundão tailings dam at an iron ore mine at the Samarco Mariana Mining Complex in Minas Gerais, Brazil, suffered a catastrophic failure, resulting in flooding that devastated the downstream villages of Bento Rodrigues and Paracatu de Baixo (40 km (25 mi) from Bento Rodrigues), killing 20 people. The extent of the damage caused by the tailings dam collapse is the largest ever recorded with pollutants spread along 668 kilometres (415 mi) of watercourses.
https://londonminingnetwork.org/2020/11/lmn-statement-for-5th-anniversary-of-the-samarco-disaster/
https://londonminingnetwork.org/tag/samarco/
BHP Billiton is facing a $5bn (£3.8bn) claim for damages over the dam collapse in Brazil.
In November 2020, the District Council of Mariana in Brazil (and other Brazilian claimants) sought leave to pursue a claim in the UK courts from the BHP Group for damages caused by the collapse of the Fundão tailings dam. This was rejected.