Trial opens over mining giant BHP's liability in 2015 Mariana dam disaster A long-awaited civil trial related to one of Brazil's worst environmental disasters, the 2015 Mariana dam collapse, is getting underway in London. More than 620,000 people, including relatives of 19 people killed in toxic mud, are having their cases heard in one of the largest lawsuits in English history. FRANCE 24's Yuka Royer speaks with Tom Goodhead, CEO of the law firm representing the claimants, about the significance of this trial.