Recent incidents in Brazil and Australia have once again put the spotlight on the safety of mining operations, and specifically their dams.
In February, Brazil’s environment authorities in the eastern Para State asked operators of the Alunorte alumina refinery to reduce operations by 50 per cent due to concerns over potential water contamination.
The authorities also ordered the halting of operations at one of two tailings dams at the Paragominas bauxite mine. The major shareholder of the firm that owns both facilities is Norsk Hydro.
Barely two weeks later, a section of the northern dam wall at the Cadia mine, located in eastern Australia’s state of New South Wales, collapsed. The incident forced the mine’s operator, Newcrest Mining, to halt operations at the mine.
Brazil is no stranger to mining disasters. In 2015, the southeastern Germano iron ore mine, which is close to the city of Mariana, experienced a breach at the Fundão dam and released 39.2 million cubic metres of waste. Nineteen people were killed, including five village residents and 14 employees of the Samarco mining firm which operated the mine. The slurry travelled 650 kilometres and ended up in the Atlantic Ocean 17 days later.
Why should we care about the impact of mine tailings and their impact on the environment? Mine tailings are one of the components of mine waste besides overburden, waste rock and water. Their physical and chemical properties vary and are dependent on factors such as the size of mined materials and their moisture content, the structure of the mined rock, and the method of processing used. They may also contain harmful material ranging from heavy to radioactive metals as well as sulphide minerals and reactants such as cyanide, which pollute the soil and vital water sources.
In November 2017, UN Environment and Norwegian foundation GRID-Arendal jointly published a report on safety at mine tailings dams.
“It is clear that in most documented failures (apart from earthquake-induced failures) there were ample warning signs beforehand. The tragedy is that the warning signs were either ignored or not recognized by under-resourced management,” said the report.
The report also noted that increased climate variability and extreme weather are also a challenge to dam safety, with heavy rain having been cited as a contributor to 25 per cent of global and 35 per cent of European tailings dam failures.
So, what needs to be done to ensure better management of tailings storage? It is important to strengthen international cooperation and coordination on mining regulation, and especially safe storage of tailings.
“Mining is an important economic activity, particularly in low- and middle-income countries. When done responsibly, it can contribute to a country’s sustainable development. Therefore, it is important that the industry continues to strive towards adopting best health, safety and environmental practices, including addressing pollution issues,” said Ecuadorian conservationist Yolanda Kakabadse.
Her sentiments were echoed by UN Environment’s Executive Director Erik Solheim during his visit to Brazil this month.
“We must place safety first by prioritizing environmental and human safety in all aspects of mining operations. Regulators, companies and communities need to embrace a policy of zero-failure objective as far as tailings storage is concerned,” said Solheim.
“Through international cooperation, countries have an opportunity to learn from each other about how to overcome obstacles to safety,” he further said.
While there is no publicly accessible inventory of tailings dams, the UN Environment and GRID-Arendal report says there could be at least 3,500 dams around the world.
It also adds that while the overall number of annual dam failures has been in decline, the number of serious incidents has increased.
Between 2007 and 2017, there were at least 10 very serious mine tailings dam failures around the world. These involved multiple loss of life, approximately 20 lives per incident and/or the release of at least one million cubic metres of water. The waste in some of these cases travelled 20 kilometres or more.
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