Avoiding tailings dam collapses requires governance, partnership and responsibility.

Silveira FAO, Gama EM, Dixon KW, Cross AT. 2019. Avoiding tailings dam collapses requires governance, partnership and responsibility. Biodiversity and Conservation.  

On November 5th, 2015, 50 million m3 of mining tailings were spilled after a dam collapse in Mariana, south-eastern Brazil. The toxic waste destroyed the entire village of Bento Rodrigues, killed 19 people, and compromised the livelihood and welfare of hundreds more people living in the Doce River watershed (Escobar 2015). Eventually, the tailings reached the Atlantic Ocean, leaving in their wake a trail of sterilised aquatic and terrestrial ecosystems (Queiroz et al. 2018). After a tragedy of such immense scale, National and State congressmen proposed more rigorous legislation to prevent further tailings storage facility failures. However, on January 25th, 2019, another dam collapsed at the Córrego do Feijão Mine near Brumadinho. Another 12 million m3 of tailings was spilled, this time in the Paraopeba watershed. Although a smaller amount of toxic waste was released, the human tragedy is set to eclipse that of the Mariana tragedy: so far 212 people have lost their lives, and nearly 93 are missing and feared dead. The Iron Quadrangle, the affected region where both tragedies occurred, is well-known for its exceptional biodiversity and endemism (Jacobi et al. 2007; Pena et al. 2017). The Iron Quadrangle is located in the state of Minas Gerais, and harbours two global biodiversity hotspots, namely the Atlantic Forest and the Cerrado (Myers et al. 2000), and is the spring of many nationally important rivers (Callisto et al. 2016). Yet it is also one of the most significant global mineral provinces, and provides over half the mineral production of Brazil. Nearly 50% of the area originally covered by ironstone outcrops has been lost due to mining activities (Salles et al. 2018). There are at least 50 tailings dams in Minas Gerais under the risk of collapse (Meira et al. 2016). Although pressure is being increasingly places upon the mining industry and regulators in Minas Gerais to ensure dam failures never happen again, Brazilians are becoming disturbingly used to these catastrophes. One month after the Brumadinho tragedy, a lew legislation banning such kinds of tailing dams has been approved. The mining industry needs to realise that storing tailings as liquid or paste in rock and mud impoundments without adequate rehabilitation or restoration is neither safe nor environmentally conscious. Merely ensuring geotechnical stability is insufficient; the dam at Córrego do Feijão had passed multiple stability tests, the most recent just months prior to its collapse. Failure to properly manage tailings and other processed mined materials results in significant cascading environmental and human welfare legacies, places biodiversity at risk, and jeopardises the economic viability of the mining industry through reduced social and environmental license to mine (Cross et al. 2017). Tailings also represent substantial chemical toxicity risks that can also be ameliorated through emerging bio-engineering. If not adequately retained and rehabilitated, leaching from tailings of process materials such as arsenic (gold extraction), hydroxide in bauxite red mud tailings as well as mobilised materials from the crushed rock are very long term contamination liabilities to groundwater, waterways and soils. Great strides are being made through biological ameliorants including converting toxic red mud residues into metasoils capable of sustaining plant growth but industry needs to do more to ensure all tailings are capable of supporting plant growth. Profitable alternatives to the storage and use of tailings in dams exist, generating products and coproducts for the construction industry (Gama 2019). There is mounting evidence that ecological restoration improves landform stability outcomes (McDonald et al. 2016), including following mining operations. Continuing to use old technology will result in future disasters. Avoiding further dam failures requires better governance, increased industry understanding, higher environmental aspiration, and international partnerships. However, achieving these will not be possible without a responsible and accountable industry that constantly dialogues with both society and the academia.