International group publishes safety guidelines for mining waste storage

AN international group of 142 scientists, community groups and NGOs from 24 countries has published guidelines to improve the safety of mining waste storage to protect communities, workers, and the environment from the risks posed by storage facilities.

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Dire consequences have been observed as the result of waste facility failures. For example, a dam owned by mining giant Vale collapsed in 2019 resulting in 259 confirmed deaths with another 11 people considered missing. The collapse damaged the environment, homes, and vehicles. In another example, the 2015 collapse of a storage facility of mining company Samarco – co-owned by Vale and BHP – caused a mudslide that buried villages and homes, killing 19 people and polluting local water supplies.

According to Safety First: Guidelines for Responsible Mine Tailings Management, tailings storage facilities (TSFs) are failing with increasing frequency and severity, and current industry standards do not adequately protect communities and ecosystems from failures. Safety First sets out 16 guidelines aimed at improving the safety of TSFs – and preventing catastrophic disasters. TSFs are used to store tailings, the waste from ore processing, a slurry of fine uneconomic rock and chemical effluent.

The first guideline is to make safety the guiding principle in the design, construction, operation, and closure of tailings facilities. The goal should be zero harm to people and the environment and zero tolerance for human fatalities.

Following the Vale dam collapse in 2019, experts alleged that the mining industry was failing to achieve safer management of tailings storage facilities as it is unwilling to spend on safer waste storage. Safety First says that without a commitment to safety, cost reduction will continue to be the driving factor in the management of tailings facilities, putting people and the environment at risk.

Safety First also recommends implementing rigorous controls for safety, noting that design, construction, operation, and closure of tailings facilities must be subject to the best available technology (BAT) and best available practices (BAP). Safety First advises that for safe operation and closure, conservative Factors of Safety (FoS) should be established and enforced at all tailings dams. In engineering, FoS is used to represent how much stronger a system is compared to how strong it needs to be for its intended load.

However, according to Safety First, FoS is a poor predictor of annual probability of failure,  which should be used alongside it. According to the report, annual probabilities of failure have been used in many industries such as aviation and aerospace since the Second World War. For tailings dams Safety First says an acceptable annual probability of failure is 0.01% when there is no potential loss of human life. When lives are at stake, it states that an acceptable annual probability of failure must be no greater than 0.001%.

Another guideline is to mandate the use of best available technology (BAT) for tailings, particularly filtered tailings. Reducing the water content in tailings increases their safety for storage, and filtered tailings have the lowest water content compared to conventional storage forms, ie slurries, thickened, or paste tailings. In filtered tailings, enough water is removed that they behave like a moist soil.

Filtered tailings also facilitate closure. Water can be drained from conventional tailings after placement, but this is not as effective for stabilisation as filtering the tailings before storage. BAT includes reducing the tailings stored above ground as much as possible, for example by maximising in-pit or underground storage.

Further guidelines include banning new tailings facilities immediately upstream from inhabited areas; banning upstream dams at new mines and closing existing upstream facilities; evaluating and characterising dam foundations and tailings to estimate their relationship to risk; gaining consent from affected communities; and ensuring that information regarding mine safety is made publicly available.

Upstream dams are not built in a single phase as with hydroelectric dams, instead the face is built up in stages – using the coarser portion of tailings – as tailings are added and their depth increases. Al Gedicks, Executive Secretary at co-publisher Wisconsin Resources Protection Council (WRPC), said that “the upstream dam construction design is an inherently risky design and poses an unacceptable risk to the health and safety of communities downstream from these structures”. WRPC aims to educate the public about the consequences of allowing mining developments in northern Wisconsin.

After the collapse of the Vale dam, which was an upstream dam, Brazil banned tailings dams built using this method.

According to Safety First, the safest tailings facility is one that is not built. To reduce the long-term liability of mine waste facilities and environmental impacts the volume of tailings produced should be reduced, as well as demand for primary raw materials. However, at least some mining will be needed moving forward – including to support energy transition technologies – and best practices are needed to do so.

Louise Hénault-ethier, Science Projects Manager at Canada’s David Suzuki Foundation, said: “While mining provides essential minerals for our societies and our energetic transition, we must ensure that these extractive activities are reduced to exploit only what is necessary and embrace a zero waste and circular economy approach. Mine tailings are a huge health and environmental hazard and leave a costly legacy to future generations. Let’s adopt the most stringent standards to maximise the efficiency and safety of the management.”

The David Suzuki Foundation, a co-publisher of Safety First, works to conserve and protect the natural environment, and help make Canada more sustainable.

Jan Morrill, International Mining Campaigner at co-publisher Earthworks, said: “Any regulations that do not meet the bar set by these guidelines do not go far enough to protect people, ecosystems and livelihoods from catastrophic failures.” 

Earthworks aims to protect communities and the environment from the adverse impacts of mineral and energy development while promoting sustainable solutions.

Lindsay Newland Bowker, Executive Director of research institute World Mining Tailings Failures, said: “[The voices of Safety First] are right that we want to prevent catastrophic failures, because we want to preserve communities, lives, lands, and waters needed to sustain life. They are right that preservation of lives and community should have a higher priority than mineral extraction.  However, they did an awkward, not-very-worthy job of delivering this simple message and in all that jumble of text that message is lost.”

The Safety First guidelines came prior to the release of the Global Tailings Standard on Tailings Management for safer management of tailings storage facilities. The Standard has been developed by Global Tailings Review. Following the Vale dam collapse, the Global Tailings Review was co-convened by the International Council on Mining and Metals, the United Nations Environment Programme, and the Principles for Responsible Investment network.

Safety First counted the Review’s 2019 draft of the Global Tailings Standard amongst industry standards that it considers inadequate. In a recent statement, the Review said that the upcoming Standard “will establish much needed robust requirements for the safer management of both existing and new tailings facilities globally”. On 25 June, the Review said it expected to publish the Standard and accompanying documents “in the coming weeks”.