Mine Tailings Storage: Safety Is No Accident

Mine tailings and tailings storage facilities Mine tailings are a major waste stream generated in mining operations. Tailings are the waste material left over after the valuable component has been removed through processing. They include ground-up rock or sand, and the chemical reagents and process water used to extract the commodity. Tailings dams, also referred to as tailings storage facilities, 1 are the most common method used to store this material.

• For many years the overall number of annual tailings dam failures has been in decline, however, the number of serious failures has increased (Bowker and Chambers 2015). • There is no publicly accessible inventory of tailings dams, however, one estimate has put the number of tailings dams at 3 500 (Davies and Martin 2000). This is likely an underestimate as there could be more than 30 000 industrial mines (SNL 2016). • The global volume of stored tailings is also unknown, but recent disasters illustrate the potential scale of accidents. For example, the Mount Polley and Samarco failures in 2014 and 2015 respectively each released more than 25 million cubic metres of tailings into the environment – combined, this represents enough material to fill more than 20 000 Olympic swimming pools. • The cost of tailings dam failures to industry can be extremely high. For example, BHP has provided US $174 million to the Renova Foundation for remediation and compensation programmes following the Samarco dam failure and is also facing a potentially costly civil claim.

Due to the physical and chemical nature of tailings, they pose potential risks to people and the environment, which means they require proper treatment and dedicated, safe storage locations. Unfortunately, tailings dams can fail. These failures can release vast quantities of water and sediment, often capable of devastating downstream communities and the environment. Some key facts: • Despite the many advances made in the mining sector and increased geotechnical engineering knowledge, tailings dam failures still occur. Since 2014 there have been seven failures significant enough to make international news. These occurred in Canada, Mexico, Brazil (x2), China, USA and Israel (WISE 2017). While not all have resulted in loss of life, they have all caused extensive damage to the environment. Six case studies of failures dating back to 1985 are described in this report. They illustrate the causes and consequences of failures, including catastrophic loss of life (a combined total of 287 direct casualties), damage to infrastructure and the environment, and the lasting impact these failures can have.

1. Tailings dams are commonly referred to as tailings storage facilities (TSF) or tailings management facilities (TMF).


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