At 3:30 p.m., a breach formed on a dam holding back iron ore waste. Operations to drain the reservoir were initiated, but the structure ruptured at 4:20 p.m. The forebay drained completely into the valley downstream, which caused a second dam to rupture. A mudslide, evaluated at roughly 60 million tons, engulfed a village having a population of 620 inhabitants. The operator notified some residents by telephone, but the list was incomplete. The plant was not equipped with alarms, as dictated by the good practices observed within the activity. There was no plan established to alert nearby populations or to evacuate.
Nineteen dead and an ecological disaster
Regarding human lives, 19 people were killed, including two children, and 50 injured. The sludge, which the operator described as non-toxic, continued to spread along the Rio Doce. Several rivers were polluted, as well as protected natural areas. Millions of fish were killed. The pollution extended all the way to the Atlantic Ocean, 650 km away. The mouth of the river, known for its ecotourism and breeding area for a species of giant marine turtle, was also affected. 280,000 people were deprived of drinking water.
Structural weaknesses were to blame
Seismic shocks were recorded in the area on the day of the accident, but the link with the failure of these embankment dams has not been established. The dam was in the process of being elevated as it was at the limit of its capacities. Accident scenarios largely minimised the magnitude of the flow of residues in the event of a collapse: they were based on the construction height established in 2008, i.e. 45 m, although the dam was double that height on the day of the accident.
Public opinion highlighted inadequate inspection of these installations by the authorities and the slow review process of the mining code, which had been under negotiation for several years. The government, which describes this event as “the biggest environmental disaster in the country,” suspended the operating license.
According to the press, the first dam had already experienced several technical incidents:
- April 2009; infiltrations up to 1 m in diameter were discovered, which had resulted in internal erosion of the structure. The reservoir was urgently emptied, and the dam was consolidated.
- 2010; the dam’s main gallery was buried by sand. The expansion joints had opened up, and a collapse and cracks were observed. The body of the dam was reinforced, the stormwater drainage system replaced, and the old galleries were filled in.
- 2013 to 2015; 4 resurgences appeared in the body of the dam. During this period, the operator increased its production by 37%, and thus also the height of the dam.
- July 2015; during the last inspection, a resurgence appeared on the right side. The drains installed to deal with the previous resurgences on the left-hand side were declared saturated. The piezometers indicated massive infiltrations in the dam’s structure.
Repairing the environmental damage
The government fined the operator 2 billion reals (450 M€) for the civil parties. It also initiated criminal proceedings against the operator for environmental crime and homicide. An agreement was signed March 2nd, 2016. The operator undertakes to pay € 5.6 billion to finance a 15-year program. Its objective is to repair the social and environmental damage caused by the disaster. In particular, the program includes the restoration of 40,000 hectares of permanent protection zones and 5,000 springs that were devastated in the river basin, and to safeguard wildlife.
In May 2016, the public prosecutor requested $43 billion from the structure’s owners. This legal action seeks to “fully” compensate for the human, economic and environmental damage caused by the tragedy.