On 7 November 2022, the eastern wall of the tailings storage facility (TSF) at Petra Diamonds’ Williamson mine in Tanzania was breached. A total of 12.8Mm³ of water and tailings materials covered an area of 4.57km² inside, and 1.5km² outside, of the mine lease area. The main portion of the tailings was contained by the New Alamasi water dam – which sits within the mine lease area. Testing confirmed that no dangerous chemicals were found within the water and tailings.
No major injuries or fatalities were reported but 286 individuals from 50 houses had to be relocated. All affected households have been provided with accommodation and humanitarian relief within the village they were displaced from. Investigations into the cause of the breach and assessments of the environmental, social and economic impact are ongoing. Production was temporarily suspended whilst the company investigated the root cause of the failure mechanism and explored options to recommence operations safely and as soon as possible.
Preliminary assessment concluded that the breach was initiated by the subsidence of a portion of the east wall of the TSF that enabled water to crest the wall. The root cause of the subsidence has not been determined and will require a forensic geotechnical investigation to be completed. This work will be undertaken by an independent company specialising in tailings dam design and management and will take between 6 and 12 months.
Precautionary measures to contain the tailings material and strengthen the New Alamasi water dam were completed in early January 2023. The creation of a safety bund, mitigating risk in the affected areas, has also been completed.
In light of the failure of the existing facility, the design of a new TSF which was already under construction at the time of the incident, is currently under review. It is now expected that this new TSF will take longer than initially anticipated to become operable. In parallel, a further potential option of repairing and using the existing TSF is also being explored as a long-term solution, but this is subject to the outcome of geotechnical investigations.
Environmental assessments, with the assistance of independent experts, continue to be carried out to determine how best to clean up or remediate affected areas. Trials are also in place to identify the best land use options post-remediation of affected areas. To date, these studies indicate that areas lying within the mining lease area are best suited to be returned to wilderness, either as forest or wetlands, through amelioration of the soil and revegetation. Areas outside of this will be treated according to the depth of the tailings material. Thinner layers of tailings can be mixed into the surrounding soil and thicker layers can be used for agricultural purposes following trials which demonstrate that enrichment with compost will enable cash crops to be farmed on a viable basis.
In addition, Petra says the vulnerability of affected people is an important consideration and a key component of this work. Psychosocial support is being provided and once any issues are identified, a mitigation process will be implemented. Alternative agricultural land is being identified to enable farming activities for those affected to recommence as soon as possible.
A comprehensive risk assessment is underway at all of the mine’s tailings facilities. Work to identify the best interim tailings storage facility is continuing with external experts from Tanzania and South Africa. Once completed a detailed report will be forwarded to the Government of Tanzania for approval. This will allow the startup of production to commence while work is being conducted on the longer-term tailings storage solution. It is anticipated that production will resume at the beginning of FY 2024.
Previously, Petra Diamonds Limited has said that it is committed to implementing the Global Industry Standard on Tailings Management (GITSM) and has made good progress, aiming to fully comply by 5 August 2023.
On 28 June 2022, its Board of Directors approved and adopted a tailings management policy which commits Petra to implementing a tailings management system for all its active and dormant tailings facilities, based on international best practices and aligned with the GISTM, relevant technical guidelines and applicable legislation.
Jagersfontein diamond mine
Earlier on 11 September 2022, a tailings dam collapsed at the closed Jagersfontein diamond mine in Free State, South Africa. The tailings flowed over 8km and left a path 1.5km wide, entering several streams and rivers including the Prosesspruit, before continuing to the Kalkfontein Dam which is used for drinking water and agricultural purposes. It is reported that at least 160 homes were damaged, one person and hundreds of animals were killed, and more than 26km² of grazing land was destroyed.
According to a Reuters report, South African authorities shut down the tailings dam in 2020 due to high water levels as then-owner Reinet Investment had exceeded authorised limits. The all-clear to resume operations was given in June 2021 as water levels had dropped.
Jagersfontein is described as being one of the oldest and largest hand-dug diamond mines in the world. Mining began in 1870 and it remained in service until the 1970s. The town of Jagersfontein and nearby Koffiefontein are home to many retired mine workers and their families.
The mine and operations were originally owned by diamond producer De Beers. Although mining had stopped, reprocessing operations were started in 2010 by Jagersfontein Development as advances in extraction technology made it possible for gems to be recovered from the old mine waste. Reinet Investments of Luxembourg became involved a year later before selling to Dubai’s Stargems Group in April 2022.
Stargems Group said it wanted to expand its presence across the diamond supply chain, and described Jagersfontein as a healthy mine production that they hoped to increase and add value to the communities it represents.
Jamie Kneen of MiningWatch Canada said: “It is clear that mining companies continue prioritising their bottom lines over community safety in tailings management. Governments must ensure that companies make safety the primary consideration in tailings facilities and dam design, construction, operation, closure and post-closure, and those measures must be independently verified.”
The co-conveners of the Global Industry Standard on Tailings Management (GISTM) – the International Council on Mining and Metals (ICMM), Principles for Responsible Investment (PRI) and the United Nations Environment Programme (UNEP) – issued a joint statement on the Jagersfontein tailings failure.
They said it underscores the critical importance of responsible tailings management and that all stakeholders – from companies to governments and investors – must urgently work to enhance the safety of tailings storage facilities across the globe.
Launched in 2020, GITSM strives to achieve the ultimate goal of zero harm to people and the environment and is described as being a step-change in terms of transparency, accountability and safeguarding the rights of people affected by mining projects.
ICMM, PRI and UNEP said they are “once again calling on wider investors, companies, communities and governments to join us in advocating for the standard’s implementation by mining companies, whether public or private – across all existing and new sites, in all jurisdictions.
“Simply put,” they added, “anything less than every tailings facility on earth being responsibly managed is just not good enough. While some companies including all ICMM members have committed to implementing the GISTM or equivalent standards, many other operators have yet to commit to doing so. We urge every mining company, everywhere to immediately embrace the standard as a top priority.”
“Tragedies like these show how communities bear the brunt of irresponsible mine waste management,” says Hassen Lorgat of the Benchmarks Foundation. “South Africa has the largest number of upstream tailings dams worldwide, a construction method that is considered unsafe and has actually been banned in some countries. Mining companies must not be allowed to simply walk away from unstable tailings dams. This means that governments must ensure the laws and practices of corporations change to protect communities and ecosystems.”
This article first appeared in International Water Power magazine.
