It was a sad day when Johannesburg’s “Top Star Drive-in” closed in 2008. Top Star was a landmark, where many local citizens had enjoyed movies and fantastic views over the city. The reason for closure was more to do with competition from cable TV than the fact that Top Star was located on top of an old gold mine tailings facility, the Ferreira dump. Today, such a location would be inconceivable.
In the last decade, tailings dam collapses across the world have become more frequent and severe. This is mainly because tailings dams are getting larger as more low-grade deposits are being exploited, according to Earthworks.org.
For example, in 2015 the Samarco iron ore mine’s tailings dam in Brazil burst, killing 19 people. An even more serious incident occurred four years later, with the failure of the Brumadinho tailings dam at the Corrego do Feijao mine, also in Brazil, where almost 300 people died. In 2022, in South Africa, the Jagersfontein tailings dam on a diamond mine in the Free State collapsed, killing two people.
Apart from the loss of life and damage to property, these disasters released huge amounts of toxic sludge into the surrounding environment. In response, the UN Environment Programme, Principles for Responsible Investment and the International Council on Mining and Metals (ICMM, in 2020 launched the Global Industry Standard on Tailings Management.
According to Earthworks.org, globally mining companies discard an estimated 180 million tons of hazardous mine waste each year. There’s an estimated 18,000 tailings dams around the world, of which 3,500 are active.
What are tailings?
Tailings are mine waste, which can be stored underground or on surface. The integrity of storage facilities, and their potential for damage, depends on their design, where they were built, the occurrence of extreme weather events, and the nature of the material stored.
For example, the waste from underground gold mining that occurred in South Africa after 1890 includes silica sand, heavy metals, toxic chemicals and in some areas, uranium – as well as a small fraction of residual gold. Dust blowing off these sites as well as water run-off was damaging the air quality and the city’s water resources, and the health effects were intensified by the intrusion of people building houses or playing (even sand-surfing) on their perimeters.
The good news is that with modern processing techniques and bulk mining, the residual gold in tailings storage facilities (TSFs) can be extracted at low cost. Reclamation simultaneously makes a profit for the operators and cleans up the environment (although even when levelled, those sites will never be suitable for residential housing).
South Africa’s gold TSFs are being re-mined by several companies, both large and small. Some companies are simultaneously mining underground, and some are specialists in mine waste management.
The older gold TSFs can yield 0.1-2.5 grams/ton of gold. Grades like this could not support a deep-level mine, but they are viable for modern open-pit mines and tailings retreatment operations. For example, Pan African Resources, which owns the long-established Barberton Mines complex in Mpumalanga, moved into tailings treatment about six years ago, and it fits into the company’s commitment to sustainable mining. The Barberton Mines Tailings Retreatment Project (BTRP) has a head grade of 1.6-2.2 grams/ton, with recoveries at around 27-43%. For comparison, the three underground mines in the Barberton complex – Fairview, Consort and Sheba – have head grades of 5-14 g/t, and their processing recoveries are above 90%.
Pan African has another tailings retreatment operations, Elikhulu at the Evander Mine, and recently concluded an agreement to buy a number of TSFs from Mintails, which is in business rescue (a process similar to Chapter 11 reorganisation in the US).