Tailings Storage Facility and Dam Management
Operational status of our dams and tailings storage facilities
The recent global tailings dam failures in the mining industry have shown the severe adverse impact these can have on human lives and the natural environment. Tailings dam integrity is consequently an ongoing area of significant focus for mining companies and investors.
Letšeng has two tailings storage facilities (TSFs) and one freshwater dam on site:
| 1. | the Patiseng TSF, which is currently in use for the deposition of coarse and fines tailings; |
| 2. | the Old TSF, which is sporadically used for fine tailings deposition; and |
| 3. | the Mothusi Dam, which is the mine’s freshwater supply source. |
Letšeng’s TSFs and dam were constructed using the centre line and downstream tipping method, being a safer method of construction than the “upstream” construction methods used in most recent dam failures reported in the mining industry.
The 2022 quarterly dam safety inspections for the Mothusi Dam were completed as scheduled. There were no adverse findings regarding the safety of the dam or the possible failure modes relating to the embankment, the spillway structure or the seepage. The exceptionally high rainfall experienced in 2021 and 2022 prompted us to request the Engineer of Record (EoR) responsible for the Mothusi Dam to provide an opinion on the safe operating level of the dam. The EoR confirmed that the dam can be safely operated at its 100% full supply capacity, subject to all operation and maintenance procedures being followed. The dam reached 100% full supply capacity in January 2023 and water started flowing down the spillway which had been extended to push the flow away from the toe of the wall.
Our TSF management code of practice is aligned to that of the ICMM’s GISTM, and we have established appropriate governance structures at both operational and Group levels to provide oversight and assurance of continued safe and responsible management of our TSFs. The relevant details of Letšeng’s TSFs are available in our voluntary disclosure as part of the Investor Mining and Tailings Safety initiative set up by the Church of England, which can be found under the Company’s name at http://tailing.grida.no/.
An external consultant was appointed to conduct geotechnical investigations to provide the technical data and information to understand the tailing storage facilities’ founding conditions and to review and update the dam breach analysis that was conducted in 2020. The outcome of this work will inform the current consequence classification of our TSFs. This work has commenced and is scheduled to be completed by Q3 2023.
There were no incidents of compromised dam or TSF integrity.
Governance framework
Our Approach
It is our responsibility to guard our workforce, communities and the environment in which we operate against any potential risks posed by our operations. TSFs, while an integral part of mining, present a significant potential hazard if not responsibly managed and continuously monitored. Focused risk management is therefore crucial at every stage of the lifecycle of our TSFs.
In response to recent tragedies, the ICMM’s GISTM was established to achieve the ultimate goal of zero harm to people and the environment. The GISTM requires operators to take responsibility and prioritise the safety of TSFs through all phases of their lifecycles, including closure and post-closure. It also requires the disclosure of relevant information to support public accountability. Gem Diamonds has committed to and adopted the GISTM standards.
We recognise that ensuring the integrity of our TSFs and freshwater storage facilities is non-negotiable and integral in exercising our responsibility to safeguard our workforce, communities and environment to ensure business continuity. We take a focused and proactive approach to managing our TSFs according to appropriate international best practice. Retaining structures and embankments undergo stringent safety monitoring in the form of inspections and audits, which are conducted both internally and externally at regular intervals throughout the year. Stringent inspections and monitoring on a daily, weekly and monthly basis include surveying various factors such as the densities of fines deposits, water levels, beach lengths and freeboard. Annual structural stability analysis is also conducted at our TSFs and an early-warning system, together with community training and awareness programmes, are used to ensure the emergency readiness of communities that could be affected in the unlikely event of a failure. The nearest village is located 20km downstream from the mine.
The findings and recommendations stemming from these investigations and audits are reported quarterly to the Boards and Sustainability subcommittees at both operational and Group level.
The Global Industry Standard on Tailings Management
The GISTM is directed at operators and applies to TSFs, both existing and to-be-built. It makes it clear that extreme consequences to people and the environment from catastrophic TSF failures are unacceptable. To this end, operators must have zero tolerance for human fatalities and strive for zero harm to people and the environment, which is directly aligned to our safety culture. The GISTM provides the specified measures to prevent failure of TSFs and to implement best practices in planning, design, construction, operation, maintenance, monitoring, closure and post-closure activities.
Our Dam and TSF Management, Monitoring and Assurance Strategy
Patiseng TSF
| Internal Inspections | External Inspections | Additional Studies | Measures in Case of Failure |
| Daily inspections and weekly surveys of water level, beach length and freeboard as well as overall TSF condition | Quarterly structural stability inspections by the appointed EoR Annual structural stability assessment by independent external expert |
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Old TSF
| Internal Inspections | External Inspections | Additional Studies | Measures in Case of Failure |
| Daily inspections and weekly surveys of water level, beach length and freeboard as well as overall TSF condition | Quarterly structural stability inspections by EoR Annual structural stability assessment by independent external expert |
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Mothusi Dam
| Internal Inspections | External Inspections | Additional Studies | Measures in Case of Failure |
| Weekly inspections | Annual dam safety inspections by EoR Quarterly dam safety inspections by Letšeng, reviewed by EoR |
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TSF Risk and Governance Management Framework
Group Risk and Reporting structure
Board
The Board of Directors is informed of the status of the TSFs providing confirmation of the following:
- All TSFs have been designed with a full understanding of the consequence of failure, site conditions and reasonably expected operating conditions.
- All TSFs are and will be constructed and operated in accordance with defined thresholds and performance indicators, with particular reference to containment integrity and overtopping risk management, and managed in accordance with the Gem Diamonds TSF Management Standard.
- Construction, operation, maintenance and surveillance of each TSF is proceeding in conformance to design intent.
- Compliance and performance are verified as part of the Gem Diamonds assurance programme, both internally and externally. Non-conformances that may increase risk to the point where the design intent may not be achieved are identified, reported and addressed.
- An emergency response plan, based on a comprehensive understanding of the consequences of failure, has been developed, implemented, maintained and tested.
- In alignment with the requirements of the recently published GISTM, the above items are independently verified by suitably qualified professionals (an external reviewer/review board) at intervals dictated by the consequence classification of each facility.
Internal Risk and Assurance
Risk and Assurance
Risk management and assessment commensurate with the consequences of failure of each facility is carried out routinely, the results of which are reviewed and overseen by independent third-party experts.Independent Tailings Review Board
Independent Technical Review Board (ITRB)
- An appointed ITRB consisting of Senior Independent Technical Reviewers (SITRs) is mandated for systematic and ongoing independent reviews.
- The ITRB provides independent technical review of the design, construction, operation, closure and management of tailings facilities. The independent reviewers are third parties who are not and have not been directly involved with the design or operation of the particular tailings facility. The expertise of the ITRB members reflects the range of issues relevant to the facility and its context and the complexity of these issues. The ITRB reports directly to the COO.
Tailings Governance Committee
Tailings Governance Committee
The Tailings Governance Committee is chaired by the COO, who reports directly to the CEO on matters related to the GISTM, communicates with the Board of Directors, and is accountable for the safety of tailings facilities and for minimising the social and environmental consequences of a potential tailings facility failure.
Engineer of Record
Engineer of Record (EoR)
The EoR is a qualified engineering firm or individual responsible for confirming that the tailings facility is designed, constructed and decommissioned with appropriate concern for integrity of the facility, and that it aligns with and meets applicable regulations, statutes, guidelines, codes and standards. Every facility has an EoR working continuously with the Responsible Tailings Facility Engineer (RTFE) and operational management to ensure construction and operational adherence to design, and that the structure is performing in line with the design intent.
Operation (RFTE and Contractor)
Competent person (RTFE)
The RTFE is an engineer appointed by Letšeng who is responsible for the tailings facilities. The RTFE must be available at all times during construction, operations and closure. The RTFE has clearly defined, delegated responsibility.
Community Engagement on TSF and dam safety
Letšeng provides the community and district-level stakeholders with balanced and objective information about the state and safety of its TSFs and freshwater storage dam. This is done during quarterly public gatherings attended by community representatives from nine neighbouring villages.
Consultations are held with these stakeholders on TSFs and dam-related safety activities and project decisions that directly or indirectly affect them. Letšeng and six of the nine neighbouring villages jointly established the downstream emergency preparedness programme. The aim of this programme is to alert the community in the event of a TSF or dam incident or any other emergency that would require the communities to evacuate from the downstream villages.
We frequently conduct in-depth training of community members on how to respond during an emergency. Emergency preparedness drills with community members are held every quarter. Assembly points have been identified and clearly marked in the villages. A two-way radio system is also in place and is regularly tested. Sirens have been installed in the six villages which are centrally controlled at the mine and manned 24 hours a day by the mine’s Emergency Team.
Stakeholder engagement platforms:
- Quarterly public gatherings with local communities.
- Daily, weekly and monthly engagement with community leaders.
- Biannual district-level stakeholder forums.
- Quarterly district leadership forums.
- Monthly district leadership meetings.
- Joint emergency preparedness drills.