Case Study: Feijão Dam B-1 (Brazil, 2019)

At 12:28pm on January 25, 2019, the B-1 tailings storage dam at the Córrego do Feijão iron ore mine near Brumadinho, Brazil, failed catastrophically, killing 272 people and causing extreme environmental damage in the Paraopeba River watershed. When the dam failed, 9.7 million m3 of liquefied mining waste was suddenly released downstream, engulfing the mine’s railway, maintenance and administration area, including a canteen where miners were having lunch. The tailings progressed rapidly downstream, destroying homes, farms, and roads. The mudflow covered an area equivalent to 450 football fields. The failure was captured on video by the mine’s onsite video cameras, showing a slope failure that developed across 80% of the face of the dam in about 5 seconds. The initial failure was followed by a series of retrogressive slope failures that progressed upwards through the tailings. Prior to the failure, the dam was extensively monitored using survey monuments along the crest of the dam, inclinometers, and piezometers. None of these methods detected any significant deformations prior to failure. Disposal of tailings at the dam stopped three years before the failure. Investigations concluded that the failure was the result of flow liquefaction within the tailings in the dam resulting from the presence of loose, saturated, heavy, and brittle tailings under high shear stress conditions. This resulted in a marginally stable dam that was close to failure in undrained conditions. The mine owner, Vale S.A., Brazil’s biggest miner, was ordered to pay $7 billion in damages to the affected communities.