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CDS I TSF, Brazil
At 10 April 2024
Coordinates: Lat -20.019186°, Long –43.492902°
Guidance Note
Refer to our guidance note.
Description and Lifecycle Design
The CDS I Fines Containment Dam is located in the State of Minas Gerais, in the municipality of Santa Bárbara, about 110km from Belo Horizonte. The CDS I TSF was constructed in 2005 and is a structure used for the containment of sediments generated by two waste-rock stacks, Carvoaria and Cachorro Bravo, as well as from two open pits, Rosalino and Mutuca. The TSF was built using the Downstream Method. It has undergone two raises with the first raise reaching an elevation of 755 Mamsl in 1998 and the second raise achieving an elevation of 758.5 mamsl in 2004. The impoundment wall is 12m high at its maximum and was constructed with an internal drainage system to ensure stability.
A spillway was constructed to enable continuous discharge of water and in 2023 and 2024, it was upgraded to cater for a Probable Maximum Flood (PMP) event as required by the Brazilian legislation.
CDS I General Information
| Facility Name | CDS I TSF |
| Start of Operation | 2005 |
| Construction Method | Downstream Earth Wall |
| Current Deposition Method | No Tailings Deposition, used for sediment control as a water storage facility |
| Dam Capacity | 400,000m3 (Actual Volume Tailings). |
| Design/License Capacity – Volume/Tonnage | 400,000m3 |
| Crest Elevation | 758.5 mamsl |
| Spillway Elevation | 756.4 mamsl |
| Maximum Height | 12m |
| Outer Wall Profile | 1V:2H (Downstream) |
Consequence Classification
| GISTM Classification | Very High |
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 with a multi-disciplinary team and in collaboration with the Engineer of Record (EoR) for each facility in line with nationally or internationally accepted best practices. This report provides a summary of the key details of the structure, including site investigation, geotechnical parameters, foundation, embankment, drainage system, spillway, monitoring and tailings disposal plan. It also details the risk-analyses methodology (using the failure modes and effects analysis method), potential failure modes along with their susceptibility and consequences, and the control and mitigation measures.
From this process, eight risks were mapped that could in theory lead to a reduction in the dam’s structural performance, with one risk was classified in the ALARP (manageable) range and the rest in the acceptable range.
For the risk in the ALARP (manageable) range, an action plan has been developed to, where possible, further reduce this risk to the acceptable range.
In addition, actions were recommended for acceptable risks and general recommendations to be applied in the operation and maintenance of the TSF. All of these action plans aim to reduce the probability of possible risks, as well as minimize 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 also the risk assessment consequence definition and the mitigation measures to be implemented.
For the CDS I TSF, the Self Rescue the Zone was mapped out for a distance of 10km. This was greater than the time for the inundation wave to cover the distance in 30 minutes as required by the Brazilian Legislation.
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 CDS I TSF is shown in the tables below.
Areas affected by Impact Zone
CDS I TSF
| Municipalities in ZAS | Santa Bárbara & Catas Altas |
| Municipalities in ZSS | Santa Bárbara & Catas Altas |
| Main Watercourses Impacted | Córrego Moinho de Olício & Ribeirão Caraça |
| Watersheds | Rio Doce |
| Areas with Potential for Interference | Private properties; infrastructure Road (MG-262) and Caraça Road (in all scenarios) and streets and bridges |
Summary of the socio-territorial characterization of the impact zone
| Type of Property | Quantity |
|---|---|
| Occupied Houses | 72 |
| Summer Houses | 1 |
| Houses without a resident | 2 |
| Entity | 1 |
| Establishment | 4 |
| Public Equipment | 2 |
| Houses under construction | 3 |
| Plot without House | 13 |
| Total Population in ZAS | 207 |
| Population with mobility difficulties | 16 |
| Population with Special Needs | 12 |
| Number of Sensitive buildings in ZAS | 0 |
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:
- EoR Inspections – Monthly, with two safety declarations submitted to the Brazilian National Mining Agency (ANM) in March and September of each year.
- Review – Annually
- AngloGold Ashanti Corporate Review – Annually
- Independent 3rd Party Regulatory Review – Annually
- Dam Safety Review (DSR) – Typically every five years
| Reviews | Most Recent Review | Next Planned Review |
|---|---|---|
| EoR | March 2024 | Monthly – 2024 |
| ITRB | July 2023 | May 2024 |
| DSR | N/A | Dec 2024 |
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 presents a 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 CDS I 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 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 2023.
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, and to the RTSs, which scans prisms 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 members of the community, was undertaken in June 2023. Training exercises have included military civil organizations (police, 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 recommendations for the population, among other self-preservation information.
A copy of the CDS I EPRP can be downloaded on the following link: BARRAGEM CDS I – AngloGold Ashanti Brasil
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 CDS I TSF and its appurtenant structures.
Guidance Note
This document provides the information required under Requirement 15.1.B of the GISTM.
This document should be read in conjunction with the information relating to AngloGold Ashanti’s tailings management practices that is available on the AngloGold Ashanti website, as well as the risk factors and other disclosures in AngloGold Ashanti’s annual report on Form 20-F for the year ended 31 December 2023 to be filed with the United States Securities and Exchange Commission (SEC) (the “Form 20-F”).
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