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At 10 April 2024
Coordinates: Lat. 6.193716°, Long. -1.718696
Guidance Note
Refer to our guidance note.
Description and Lifecycle Design
The South Tailings Storage Facility (STSF), also known as Sansu TSF, was originally designed by AGC Woodward – Clyde of Australia in 1990. It was commissioned in 1991, with the aim of offering a storage capacity for a period of 20 years, based on a plant throughput of 2.2 million tonnes annually. The STSF is located approximately 4km northwest of both the Sulphide Treatment Plant (STP) and the Oxide Treatment Plant (OTP). The TSF starter embankments were built with compacted lateritic material. The TSF was continuously raised from 1991 to 2002 using an upstream cycloning method. From 2002 to 2015, the embankments were raised using a hybrid system of the paddock method with a laterite skin. In 2008, a 50m step-in construction was completed along the north and west embankments at elevation 205mamsl to improve the overall stability of the facility.
The facility is an upstream ring dyke structure, with four primary embankments: north, south, east, and west embankments . The crest elevation for the primary embankments is 217mamsl. Waste rock buttresses have been constructed at the north and west embankments to elevations 205 and 185mamsl respectively.
The facility is approaching its end of life with tailings deposition planned to cease in Q1 2028. The STSF final closure basin landform is a water shedding dome shape and as such the aim is to accomplish that by using tailings deposition to create the closure shape. Four step-ins’ embankments have been permitted by the regulatory authorities. The first step-in i.e. the Step-in 1 design is completed, and construction commenced in September 2024. The Step-in 1 embankment elevation is 219.5mamsl and is constructed into the basin to best fit the closure landform.
Tailings is deposited on the STSF through sub-aerial spigoting method via HDPE spigot pipes spaced at 25m centres and operated with pinch valves or knife gate valves.
Supernatant water is returned to the plant through a decant system comprising the northern operational penstock to Holding Pond 1 and a standby barge-mounted pump. The east penstock has been recently decommissioned as part of the Step-in 1 works. The south emergency penstock is maintained as the emergency spillway and is tested biennially.
Historically, deposition of tailings on the facility ceased in November 2015 when the mine was placed in a limited operating phase (care and maintenance). The facility was recommissioned in December 2019. The recommissioning of the TSF formed part of the Obuasi Redevelopment Project and commenced in 2021.
AngloGold Ashanti has an internal corporate tailings management team including an accountable executive. AngloGold Ashanti has appointed an internal Responsible Tailings Facility Engineer (RTFE) an external Engineer of Record (EoR) and an Independent Tailings Review Board (ITRB) at this facility to oversee and govern the design, construction, operations, maintenance, and surveillance of the facility.
South TSF General Information
| Period of Operation | 1992-2015, 2021-current |
| Construction Method | Upstream with saprolite borrow material for embankment raises. Localised rock-fill buttressing. |
| Facility Footprint (ha) | 215 |
| Step-in 1 Embankments Elevation (mRL) | 219.5 |
| Perimeter embankment height (m) | North – 54.0 South – 29.50 West – 53.5 East – 25.5 |
| Current Deposition Method | Single cell, rotational sub-aerial spigot deposition |
| Deposition area (ha) | 123 |
| Current Tailings Volume / Tonnage | Approximately 60.1Mt |
| Outer Wall Profile | 1V : 3H (maximum) |
Consequence Classification
| GISTM Consequence Classification | Very High |
Risk Assessment
AngloGold Ashanti’s comprehensive risk management plan aims to implement designs and controls in a way that risks are eliminated risks and where any risks remain, these are mitigated so that the residual risk is a As Low As Reasonably Practicable (ALARP).
Risks are considered in the design stages with mitigation measures incorporated into the design features and operational procedures. Risks are also identified and mitigated through numerous layers of reviews and inspections with follow up actions and recommendations developed to mitigate identified risks. A Potential Failure Modes Assessment was undertaken with a multi-disciplinary team and in collaboration with the EoR. Current and residual risks associated with potential failure modes are reviewed annually to identify additional mitigation measures or controls that can be adopted to further reduce the risks to ALARP.
Impact Assessment
The impact of a potential flow failure has been assessed considering the impact to human health and life, the environment, social and cultural impacts, as well as the infrastructure and economic impacts. These potential impacts have been used to inform the TSF Classification and also the risk assessment consequence definition and the mitigation measures to be implemented.
Modelling of a potential failure indicates that the areas to the south and east of the South TSF could be affected and could impact human settlements, farming, and water resources
Performance Reviews
AngloGold Ashanti has a comprehensive Tailings Review System which incorporates reviews from multiple levels and internal and external parties. All AngloGold Ashanti TSFs are subject to the following reviews:
- RTFE Performance Reviews – typically quarterly
- EoR Inspections – typically quarterly and Annual Performance Reviews
- ITRB Review – Annually
- AGA Corporate Review – Annually
- Independent 3rd Party Regulatory Review – Quarterly
- Dam Safety Review – Typically every five years
| Reviews | Most Recent Review | Next Planned Review |
|---|---|---|
| EoR | Mar 2025 | Q2 2025 |
| ITRB | July 2024 | Q3 2025 |
| DSR | NA | 2026 |
AngloGold Ashanti has adopted the following ranking system for independent reviews: Priority 1 actions are classified as a material finding.
Priority 1 – A dam safety issue considered immediately dangerous to life, health or the environment, or at significant risk of regulatory enforcement.
Priority 2 – If not corrected, a concern that could result in a dam safety issue leading to injury, health impact or discontinuity of operations.
Priority 3 – Single occurrence of deficiency or non-conformance that alone would not be expected to result in dam safety issues, discontinuity of operations or regulatory intervention.
Priority 4 – A recommendation based on good practice, improvement, or risk reduction.
No material findings (Priority 1) have been identified for the STSF in the most recent reviews.
Environmental and Social
Environment and Social monitoring programmes form part of AngloGold Ashanti’s Health, Safety, Environment (ISO14001) and Social Communities (HSEC) management systems, which act to fulfill the environmental social management system requirements under the GISTM. These environment and social monitoring programmes are comprehensively reviewed, and mitigation measures implemented as and where required. Further information on of our environment and social monitoring programmes, and performance results can be found in AngloGold Ashanti’s Sustainability Reports.
There is potential for ground water seepage from TSFs and ground water conditions around all our TSFs are regularly monitored. Where groundwater impact plumes exist, their migration is modelled and managed, as necessary to avoid interaction(s) with potential receptors.
No material findings were made in relation to the TSF in the most recent reviews.
An easily accessible and effective grievance mechanism has been implemented so that any formal complaints can be submitted by stakeholders and resolved.
Emergency Response and Preparedness
The mine has a dedicated Emergency Response Team and Emergency Management and Response Plan (EMRP). The EMRP identifies potential events and incidents, defines those personnel responsible for implementation of the response, and describes procedures for notification, communication and escalation of the emergency response.
The TSF emergency preparedness and response planning is a dedicated plan that is appended to the site wide EMRP and the facility operation, maintenance and surveillance manual. In the event of a tailings dam related emergency, the Emergency Response Team would be the first responders.
Financial Capacity
AngloGold Ashanti confirms it has adequate financial capacity to cover the estimated costs of planned closure, early closure, reclamation, and post-closure monitoring and maintenance of the STSF and its appurtenant structures.
Guidance Note
Certain statements contained in this document, other than statements of historical fact, including, without limitation, those concerning the economic outlook for the gold mining industry, expectations regarding gold prices, production, total cash costs, all-in sustaining costs, cost savings and other operating results, return on equity, productivity improvements, growth prospects and outlook of AngloGold Ashanti’s operations, individually or in the aggregate, including the achievement of project milestones, commencement and completion of commercial operations of certain of AngloGold Ashanti’s exploration and production projects and the completion of acquisitions, dispositions or joint venture transactions, AngloGold Ashanti’s liquidity and capital resources and capital expenditures, the consequences of the COVID-19 pandemic and the outcome and consequences of any potential or pending litigation or regulatory proceedings or environmental, health and safety issues, are forward-looking statements regarding AngloGold Ashanti’s financial reports, operations, economic performance and financial condition.
These forward-looking statements or forecasts are not based on historical facts, but rather reflect our current beliefs and expectations concerning future events and generally may be identified by the use of forward-looking words, phrases and expressions such as “believe”, “expect”, “aim”, “anticipate”, “intend”, “foresee”, “forecast”, “predict”, “project”, “estimate”, “likely”, “may”, “might”, “could”, “should”, “would”, “seek”, “plan”, “scheduled”, “possible”, “continue”, “potential”, “outlook”, “target” or other similar words, phrases, and expressions; provided that the absence thereof does not mean that a statement is not forward-looking. Similarly, statements that describe our objectives, plans or goals are or may be forward-looking statements.
These forward-looking statements or forecasts involve known and unknown risks, uncertainties and other factors that may cause AngloGold Ashanti’s actual results, performance, actions or achievements to differ materially from the anticipated results, performance, actions or achievements expressed or implied in these forward-looking statements. Although AngloGold Ashanti believes that the expectations reflected in such forward-looking statements and forecasts are reasonable, no assurance can be given that such expectations will prove to have been correct.
Accordingly, results, performance, actions or achievements could differ materially from those set out in the forward-looking statements as a result of, among other factors, changes in economic, social, political and market conditions, including related to inflation or international conflicts, the success of business and operating initiatives, changes in the regulatory environment and other government actions, including environmental approvals, fluctuations in gold prices and exchange rates, the outcome of pending or future litigation proceedings, any supply chain disruptions, any public health crises, pandemics or epidemics (including the COVID-19 pandemic), the failure to maintain effective internal control over financial reporting or effective disclosure controls and procedures, the inability to remediate one or more material weaknesses, or the discovery of additional material weaknesses, in the Company’s internal control over financial reporting, and other business and operational risks and challenges and other factors, including mining accidents.
For a discussion of such risk factors, refer to AngloGold Ashanti’s annual report on Form 20-F for the financial year ended 31 December 2024 filed with the United States Securities and Exchange Commission (SEC). These factors are not necessarily all of the important factors that could cause AngloGold Ashanti’s actual results, performance, actions or achievements to differ materially from those expressed in any forward-looking statements. Other unknown or unpredictable factors could also have material adverse effects on AngloGold Ashanti’s future results, performance, actions or achievements. Consequently, readers are cautioned not to place undue reliance on forward-looking statements.
AngloGold Ashanti undertakes no obligation to update publicly or release any revisions to these forward-looking statements to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events, except to the extent required by applicable law. All subsequent written or oral forward-looking statements attributable to AngloGold Ashanti or any person acting on its behalf are qualified by the cautionary statements herein.