Ensuring the highest standards of tailings management

Dams are an integral part of mining. They are used to impound waste, store water for mine use, control runoff to prevent flooding of mine facilities, and collect and prevent sediment from running off the mine. Dams remain key areas of risk; however, as impounded material – be it water or liquid-borne solid waste – can present a hazard to miners and communities if the dam were to fail. Indeed, tailings dam failures in Canada in 2014 and Brazil in 2015 have shown that risk management at every stage of the lifecycle of a tailings dam must always be top of mind.

The term tailings refers to the collected waste materials produced after the extraction of minerals and metals from mined ore, or, in our case, the extraction of diamonds from the kimberlite ore. It is a substance that consists chiefly of powdered rock and water. The aim of tailings management is to provide safe, stable and economical storage of tailings so as to protect community health and safety, as well as safeguard the surrounding environment.

Unlike dams that store water or generate hydroelectric power, tailings dams are not designed and built all at once. They are gradually raised to meet mine requirements according to the life of mine planning. Once constructed, the intention is for them to remain long term during which time they will dry out and will be revegetated.

At our mine sites, we ensure full lifecycle management of our tailings storage facilities that span the conception, investigation, design, construction, operation, decommissioning and closure phases. Our mine plans are in line with national regulations on waste management and storage in Lesotho and Botswana. The SEMP assessments conducted at our mines help us to keep track of our adherence to this legislation. The dams are built and maintained according to the highest structural and environmental standards.

Patiseng is our active coarse and fine tailings storage facility at our Letšeng mine. In line with the plans for the mine’s expansion, during the year, the Patiseng TSF wall was fortified to ensure it is capable of retaining the tailings material for the next phase of development of the mine in line with the overarching plans for the life of the mine. This is just one of many wall expansion phases that will continue over the years to come to ensure that the highest safety standards are maintained. In addition, the dam is closely monitored via a V-notch weir, which determines the flow rate and is connected to a flow monitoring system. Facility risk assessments, resistivity surveys and flow model studies are also regularly carried out to ensure responsible management of the facilities. The same monitoring is performed for our inactive TSF.

Ghaghoo currently has two TSFs, with a third under construction. Internal inspections on the dams are carried out daily, with structural stability inspections being made on a weekly basis. An outsourced consultancy firm conducts external quarterly inspections.

Safety is our top priority. We maintain facilities that are safe and adhere to best practice design and management standards because we believe that we hold a duty of care towards our people, our communities and the environment that surrounds our mine. We, therefore, ensure that the strictest management plans are put in place. It is our priority that complete stability and conformity to the established system are maintained at all times.

Patiseng tailings facility.