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At June 2025
Coordinates: Lat -19.866392°, Long -43.727225°
Guidance Note
Refer to our guidance note.
Description and Lifecycle Design
The Cuiabá TSF is a cross-valley earth fill impoundment that was designed and constructed as a water-retaining structure in 2005. The structure is a homogeneous compacted fill, with a vertical filter constructed for each raise, connected by horizontal drains between them, making a stepwise pattern, and a blanket drain on top of the foundation. The TSF is currently at an elevation of 904mamsl and has a maximum height of 97m. A spillway is positioned in the right-hand shoulder of the TSF. The spillway is at an elevation of 902 mamsl and has been constructed as a rectangular concrete channel.
Chronology of TSF raises:
- 2005: Initial embankment constructed to Elevation 868.00 mamsl.
- 2009: Raised to Elevation 873.00 mamsl.
- 2011: Raised to Elevation 889.00 mamsl.
- 2015: Raised to Elevation 904.00 mamsl.
In 2021, the spillway structure of the Cuiabá TSF was modified, involving the raising of the spillway crest from elevation 901.50 meters to elevation 902.00 meters and in 2022, the construction of the spillway system was completed. The final channel of this system is integrated into the dam buttress project, as detailed in the project report. The current spillway system consists of a rectangular weir at elevation 902.00 meters, followed by a gallery beneath the existing access road and a rectangular channel downstream of the gallery, which includes both smooth and stepped sections. The gallery is rectangular, with a base width of 2.50 meters and a height of 1.20 meters. The downstream channel has a base width of 2.50 meters and a height of 2.00 meters. Downstream of the spillway channel, there is a rockfill energy dissipation basin with an approximate width of 8.00 meters, a height of 3.71 meters, and a length of 26.21 meters.
The Cuiabá TSF is currently undergoing decharacterisation works, which include two construction phases. Phase I encompasses the disposal of compacted filtered tailings downstream of the dam, which are protected by waste-rock, forming a buttress for the dam. Phase II includes the disposal of filtered tailings inside the dam reservoir.
Cuiabá TSF General Information
| Facility Name | Cuiabá TSF |
| Start of Operation | 2007 |
| Construction Method | Downstream Earth Wall |
| Current Deposition Method | Deposition of Filtered Tailings to meet the closure design. |
| Target Annual Deposition Rate | De-characterisation of the TSF in progress |
| Current Tailings Volume | 11.7Mm3 |
| Design/License Capacity – Volume/Tonnage | 11.7Mm3 |
| Crest Elevation | 904 mamsl |
| Spillway Elevation | 902 mamsl |
| Maximum Height | 99m |
| Outer Wall Profile | 1V:2H (Downstream) |
Consequence Classification
| GISTM Classification | Extreme |
Risk Assessment
AngloGold Ashanti’s comprehensive risk management system uses designs and controls to eliminate risks and where there are remaining risks, these are mitigated such that the residual risk is a As Low as Reasonably Practicable (ALARP).
Risk assessments are conducted by a multi-disciplinary team in collaboration with the Engineer of Record (EoR) for each facility in line with nationally or internationally accepted best practices. The risk assessment report provides a summary of the key details of the structure, including site investigations, geotechnical parameters, foundation conditions, embankment properties, drainage system details, spillway details, monitoring criteria, and the tailings disposal plan. It also details the risk-analyses methodology (using the qualitative bowtie method), potential failure modes along with their susceptibility and consequences, and the control and mitigation measures.
In the risk analysis conducted in 2024, 10 risks were mapped that could, in theory, lead to a reduction in the dam’s structural performance, and all risks were classified as acceptable. Actions were recommended for these risks and general recommendations to be applied in the operation and maintenance of the TSF. All these action plans aim to reduce the probability of possible risks, as well as minimise possible impacts resulting from occurrences in the structure.
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 the risk assessment consequence definition and the mitigation measures to be implemented.
The impact zone covers a distance of 77.4km downstream of the Cuiabá TSF, the Self-Rescue zone (ZAS) extends to 10,6km and the Secondary-Rescue Zone (ZSS) 66.8km.
The municipalities and areas affected by the impact zone and the main social information of the potential floodplain in the event of the rupture of the Cuiabá TSF is shown in the tables below.
Areas affected by Impact Zone
Cuiaba TSF
| Municipalities in ZAS | Sabará (MG) & Caeté (MG) |
| Municipalities in ZSS | Sabará (MG), Belo Horizonte (MG), Santa Luzia (MG), Lagoa Santa (MG) & Raposos (MG). |
| Main Watercourses Impacted | Córrego Padrão, Córrego Padrão, Córrego Padrão, Ribeirão Sabará, Córrego do Gainha, Córrego da Rocinha, Ribeirão Sabará, Córrego Caeté, Ribeirão do Gaia, Córrego Padrão, Rio das Velhas, also covering Ribeirão Arrudas, Ribeirão da Laje or Bom Destino, Ribeirão Vermelho, Ribeirão das Bicas, Ribeirão Baronesa, Ribeirão do Gaia, Ribeirão da Mata, Córrego Malheiros, Córrego Campo Santo Antônio, Córrego das Lajes, Córrego Quarta-Feira ou Cachoeira, Córrego Frio, Córrego Capitão, Córrego do Inferno & Córrego Bombinha ou Grajaú |
| Watersheds | Rio das Velhas |
| Areas with Potential for Interference | Private properties – permanent presence of people; Road infrastructure (MG-030, AMG-150, MG-437, MG-262, BR-381, AMG-145 and MG 020), Streets and bridges; Commercial, industrial establishments, religious buildings, as well as inns and historical and heritage sites. |
Summary of the socio-territorial characterization of the impact zone
| Type of Property | Quantity |
|---|---|
| Registered properties | 274 |
| Residences | 236 |
| Building | 18 |
| Economic activity | 14 |
| Entities and public agencies | 6 |
| Total Population in ZAS | 1,010 |
| Population with mobility difficulties | 363 |
| Population with Special Needs | 78 |
| Number of Sensitive buildings in ZAS | 6 |
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 – monthly inspections
- EoR Inspections – Monthly, with two safety declarations submitted to the Brazilian National Mining Agency (ANM) in March and September of each year.
- Independent Review of the Emergency Response and Preparedness Plan (EPRP) – Annually
- ITRB Review – Annually
- AngloGold Ashanti Corporate Review – Annually
- Dam Safety Review (RPSB)– Typically every three years or when change TSF
| Reviews | Most Recent Review | Next Planned Review |
|---|---|---|
| EoR | May 2025 | Monthly – 2025 |
| ITRB | October 2024 | October 2025 |
| RPSB | September 2022 | October 2025 |
AngloGold Ashanti has adopted the following ranking system for independent reviews:
Priority 1 – A dam safety issue considered immediately dangerous to life, health or the environment, or presents a significant risk of regulatory enforcement. Requires immediate action and to be completed as soon as practically possible but certainly within 2 months
Priority 2 – If not corrected, a concern that could result in a dam safety issue leading to injury, health impact or discontinuity of operations. Requires immediate planning and completion by a date and specified by operations but as a minimum within 5-6 months
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. Requires that measures be taken no later than a date that would prevent escalation, but no later than one year
Priority 4 – A recommendation based on good practice, improvement, or risk reduction. Recommendation towards best practices and mitigating risk associated.
No Priority 1 recommendations have been issued by the ITRB for the Cuiaba TSF.
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 fulfil 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 interactions with potential receptors.
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
Emergency preparedness and response planning (EPRP) relies on an emergency notification system that consists of remote stations equipped with sirens that are linked to the control room at the Queiroz plant, which scans tiltmeters located on the dam face. Manual activation of the sirens is available locally as redundancy. Mobile sirens are also installed on emergency vehicles that are assigned to predefined emergency routes as an additional notification measure.
The latest dam breach study was conducted in May 2022, and an EPRP training exercise, involving community members, was documented as having been undertaken in March 2025. Training exercises have included military civil organisations (police and fire) for various communities.
The escape routes and meeting points are sign posted. These were developed based on the zone of influence, in which a maximum walking distance of 1,000m was considered to allow a quick and safe route to meeting points. The meeting point signage has information such as telephone numbers of emergency agencies and safety recommendations for the population, among other self-preservation information.
A copy of the Cuiabá TSF EPRP and be downloaded on the following link: https://www.anglogoldashanti.com.br/barragens/nossas-barragens/barragem-cuiaba/
Financial Capacity
AngloGold Ashanti confirms it has adequate financial capacity to cover the agreed share of estimated costs of planned closure, early closure, reclamation, and post-closure monitoring and maintenance of the Cuiabá TSF 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.