On 5 November 2015, a catastrophic tailings dam failure occurred at an iron ore mine in Brazil. The reported death toll from the event was 17 and 200 homes in the Bento Rodrigues are of Mariana were destroyed. The tailings dam breach caused a flood of 60 million cubic meters of waste to flow across the area and into the Doce River. A little over two weeks later, the polluted water reached the Atlantic Ocean.
The tragic event at the Samarco mine operation, which was jointly owned by BHP Billiton Ltd and Vale SA, was revisited in early November 2016 during the 5th National Debate on Safety of Failed Dams: Lessons from Mariana – One year later. ” The gathering of engineers, mining officials, government representatives, and other stakeholders was held at the Pontifical Catholic University of Rio de Janeiro (PUC-Rio).
Approximately 350 attendees packed the auditorium while others followed on a live webcast.
The Brazilian Association of Soil Mechanics and Geotechnical Engineering (ABMS) convened the event, which also welcomed the Brazilian Committee of Dams (CBDB), the National Engineering Academy (ANE), and the Engineering Club of Rio de Janeiro.
Engineer Alberto Sayão, who is a former ABMS president, has played an active role over the past year in organizing constructive dialogue on tailings dam safety.
“With events such as COBRAMSEG 2016 in Belo Horizonte, the 8th Luso-Brazilian Congress in Portugal, and the event organized by CBDB, there have been eight events on the theme held just this year—all of which enjoyed great public participation,” Sayão noted in an ABMS release.
REVISITING THE TAILING DAM FAILURE
“This most recent debate was divided into a two-day session, which made it much denser event than the previous ones,” said engineer Flavio Miguez de Mello, honorary chairman of the CBDB and titular member Of ANE.
Highlights of the conference include a speech by the Rector of PUC-Rio, Fr. Josafá Siqueira on the lessons learned from the Mariana disaster from ethical and environmental points of view and the risk management lecture delivered by Prof. André Assis, President of ABMS. Additionally, professor and engineer Fernando Olavo Francis steered collaborative discussions.
Flavio Miguez de Mello, honorary president of the CBDB and ANE member, provided a lecture on the current state of tailing dam technologies and options in design and construction, which gave the audience standard knowledge from which to interpret the subsequent discussions.
“Soon after the accident, there were several demonstrations against the use of tailings dams,” Miguez said, “with the claim that they were not safe. The state of Minas Gerais itself adopted a position of not licensing more tailings dams. However, about half of the accidents involving tailings dams in Brazil and in other countries were [not of current] construction methodologies. [To call all tailings dams unsafe] is incorrect; if the project is well done and the work is well executed and monitored, there is not a problem in building these structures in regions of very low seismicity.”
Miguez emphasized that conclusion as one of the biggest takeaways from the ABMS event, a conclusion that is also rooted in extensive research by the International Commission on Large Dams.
MORE WORK TO DO
The participants could agree on the need for more information being gathered and openly shared.
“One year after the event, we do not yet have enough concrete and in-depth information about the accident,” said Jean Pierre Rémy, an engineer with Mecasolo and a former president of the Rio de Janeiro chapter of ABMS. “The statements and reports released so far are insufficient for the technical community.”
Rémy highlight the inadequacy of this for engineering, citing how after aviation accidents issues are studied in-depth so that the international aviation engineering community can work to prevent that type of accident from occurring again. In geotechnical engineering, though, the mission seemed to be “more concerned about finding guilt than learning from mistakes.”
ABMS stressed that while Rémy’s comments are important, we must not lose sight of the importance of the technical community mobilizing to discuss the fundamental issues of tailings dam failure.
Rémy agreed.
“Even with the general feeling of frustration at the lack of technical information about the accident, dam safety events should continue,” he said. “The technical community evolves with each meeting, and in looking for facts we can transform them into lessons.”
ADDITIONAL RESOURCES
ABMS shared links to two works related to the discussions of the 5th National Debate on Safety of Failed Dams (articles in Portuguese):
“Dams and Dam Failures” – Alberto Sayão and Flavio Miguez de Mello, published in the magazine Foundations & Geotechnical Works (March 2016)
“The Lessons of Mariana” – Josafá Carlos de Siqueira
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This story is based on reporting of ABMS, Bruno Pedroni of Geosynthetica.net.br, and previous reports from Geosynthetica.
