SUSTAINABILITY

Residue storage facility and dam management

Operational status of dams and residue storage facilities

We are dedicated to managing our residue storage facilities (RSFs) and water storage dams in a way that safeguards the health, safety, and well-being of our employees and communities, while also protecting our property and the natural environment. We adhere to high standards that align with both national and global best practices for health, safety, and environmental preservation throughout every phase of the RSFs’ and water dams’ lifecycle. To this end, Letšeng has reviewed all applicable international standards, codes and guidelines related to responsible RSF management and aligned our Residue Management System (RMS) to the Conformance Protocols on the Requirements of the Global Industry Standard on Tailings Management (GISTM) published by the International Council on Mining and Metals (ICMM). Our Operational and Maintenance System (OMS), along with our RMS, seamlessly integrates people, resources, processes, and practices related to RSF and water storage management. This integration supports the achievement of our performance objectives, promotes effective risk management, and ensures the safe and responsible operation of our facilities.

Letšeng has two RSFs and one freshwater dam on site:

• the Patising RSF, which is currently in use for the deposition of coarse and fine residue from the process plants;
• the Old RSF, which is no longer used for active deposition but rather for stormwater management and rehabilitation trials to inform further concurrent rehabilitation; and
• the Mothusi Dam, which is the mine’s freshwater supply source.

All internal and external reviews of Letšeng’s RSFs and freshwater dam have confirmed their sound structural integrity and effective operational controls, with no concerns raised regarding the overall integrity of the facilities. The condition of the RSFs and water storage dams is continuously monitored, well managed, and reported at the relevant governance structures and forums.

In accordance with GISTM Principle 4, RSF owners are required to assess the downstream conditions documented in the knowledge base and determine the consequence of failure classification (CCS) for the RSFs, selecting the classification corresponding to the highest CCS for each category. This assessment and classification selection must be based on credible failure modes and should be defensible and well documented.

When adopting the GISTM, a provisional classification of "Extreme" was initially assigned, pending the completion of technical and investigative work. The review of the CCS was prompted by the findings from this work, which included geotechnical investigations to develop stratigraphic models, stability analysis and dam break assessments. Based on this technical information, specialist studies, and the guidelines provided by the GISTM, the consequence classification for the Letšeng RSFs has been updated as follows:

• Patising RSF: Reclassified from "Extreme" to "Significant".
• Old RSF: Reclassified from "Extreme" to "Significant".

The design criteria, assumptions, and management practices adopted for the Letšeng RSFs have, however, remained consistent with those of facilities classified in the higher-risk “Extreme” category. This approach is further endorsed by the Independent Tailings Review Board (ITRB), ensuring that the RSFs are managed according to the highest standards of safety and risk mitigation.

Stringent inspections and monitoring are carried out on a daily, weekly, and monthly basis, focusing on factors such as the densities of fines deposits, water levels, beach lengths and freeboard. Additionally, an annual performance report, including a structural stability analysis, is conducted for our RSFs. An early-warning system, alongside community training and awareness programmes, ensures emergency preparedness for communities that could be affected in the unlikely event of a failure. The nearest village is located more than 20km downstream from the mine. The findings and recommendations from these inspections and audits are regularly reported to the Boards and Sustainability subcommittees at both Letšeng and Group levels.

We remain committed to proactively managing our RSFs in accordance with international best practices. Retaining structures and embankments undergo rigorous safety monitoring through both internal and external inspections and audits conducted at regular intervals throughout the year. Periodic and annual inspections of the facilities conducted by the appointed Engineer of Record (EoR) and Independent Tailings Review Board (ITRB) have reported no issues or concerns regarding the stability or management of these facilities. There have been no incidents of compromised dam or RSF integrity to date.

Refer below for full details on our RSF governance framework and assurance strategy.

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. RSFs, 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 RSFs.

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 RSFs 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 RSFs 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 RSFs 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 RSFs 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 RSFs, both existing and to-be-built. It makes it clear that extreme consequences to people and the environment from catastrophic RSF 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 RSFs and to implement best practices in planning, design, construction, operation, maintenance, monitoring, closure and post-closure activities.

Our dam and RSF management, monitoring and assurance strategy

Storage facility

Electronic channels

Written communication

Direct interaction

Media

Patising RSF

Daily inspections and weekly surveys of water level, beach length and freeboard as well as overall RSF condition

Quarterly structural stability inspections by the appointed EoR Annual structural stability assessment by independent external expert

Facility risk assessment Inundation studies with flow modelling Geotechnical characterisation

Emergency assessments and planning for wall failures Communication towers in downstream villages Mobile phone contact with communication custodians Alarm activation from within villages or Letšeng emergency control centre Business continuity planning

Old RSF

Daily inspections and weekly surveys of water level, beach length and freeboard as well as overall RSF condition

Quarterly structural stability inspections by EoR Annual structural stability assessment by independent external expert

Facility risk assessment Inundation studies with flow modelling Geotechnical characterisation

Emergency assessments and planning for wall failures Communication towers in downstream villages Mobile phone contact with communication custodians Alarm activation from within villages or Letšeng emergency control centre Business continuity planning

Mothusi Dam

Weekly inspections

Annual dam safety inspections by EoR Quarterly dam safety inspections by Letšeng, reviewed by EoR

Facility risk assessment Flow modelling study Resistivity surveys

Emergency assessments and planning for wall failures Communication towers in downstream villages Mobile phone contact with communication custodians Alarm activation from within villages or Letšeng emergency control centre Business continuity planning