Ensuring the safety and integrity of our dams
We recognise that the potential risk posed by both our tailings storage facilities and raw water dams necessitates a proactive approach to risk management at every stage of the lifecycle of our facilities.
We monitor three facilities at our Letšeng mine: the Patiseng tailings storage facility (TSF), the old TSF, and the Mothusi Dam – our fresh water supply resource. Our dams are built and maintained according to the highest structural and environmental standards, using international best practice guidelines to inform our approach. Dam safety is a standing agenda item at operational HSSE Sub-Committee meetings, Group HSSE Sub-Committee meetings, and Group Board meetings where findings from our stringent safety monitoring processes, including internal and external inspections and audits, are discussed and regularly reviewed.
Our tailings storage facilities are not designed and built all at once. They are constructed in accordance with downstream construction methods and expanded to meet mine requirements according to the life of mine planning. Patiseng is our active tailings storage facility at our Letšeng mine.
Water levels at our dams are rigorously managed. All facilities have V-notch weirs that determine the flow rates and are connected to flow monitoring systems with safety limits set to trigger alerts if the measured flows are higher or lower than the established limits. Therefore, in the case of a prolonged period of rain or snow, the operation will be able to monitor any increases in water flow through the V-notches and identify possible at-risk scenarios.
All facilities undergo stringent inspections on a daily, weekly and monthly basis, surveying various factors such as water level, beach length and overall structural stability. Facility risk assessments, resistivity surveys and flow model studies are also regularly carried out to ensure responsible management of the facilities. In addition to in-house monitoring, audits by external consultants are routinely performed. Any identified risks are mitigated and required remedial steps implemented. Quarterly structural-stability inspections are carried out by an independent civil-engineering specialist.
To safeguard our host communities, an early-warning system, together with community training and awareness programmes are used to support emergency response readiness in the unlikely event of a failure. The alarm is activated from the central control centre located at the mine’s emergency room and can also be activated by community members should they become aware of an emergency. In December 2018, a Patiseng dam wall failure drill was conducted to determine the mine’s capacity to respond to a crisis. Information gathered was integrated into our plans going forward.