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CDS II TSF, Brazil
At 10 April 2024
Coordinates: Lat -19.984809°, Long -43.472180°
Guidance Note
Refer to our guidance note.
Description and Lifecycle Design
The CDS II TSF is located in the state of Minas Gerais, in the municipality of Santa Bárbara and about 110 km from Belo Horizonte. The TSF is a conventional valley impoundment with a main embankment to the south of the TSF and a saddle wall just east of the old decant pump platform. The CDS II TSF was built using the Centerline Method, totaling nine raisings, the last of which took place in 2018, with a final height of 84m (elevation 816 mamsl) and a crest length of 538m.
The main embankment is made of a homogeneous compacted fill, with an internal drainage system composed of a chimney filter and horizontal blanket drain. A reinforcement buttress has been constructed at the toe of the facility to an elevation of 807mamsl. The spillway is located on the left abutment of the main wall at an elevation of 814.33 mamsl.
In 2015, a saddle wall was constructed to close the topographic contour of the reservoir due to the final dam raising. It is 13m high, 170m long, with a crest width of 4m. Its embankment is compacted soil and internal drainage, composed of a vertical filter and horizontal blanket, both made of sands and an HDPE liner covers the inside slope of the wall.
The decharacterisation plan for the CDS II TSF consists of:
- Phase I: Constructing a buttress downstream of the CDS dam made of compacted filtered tailings and waste rock, this is currently in progress.
- Phase II: Stacking filtered tailings on top of the facility and constructing associated surface drainage works.
CDS II TSF General Information
| Facility Name | CDS II TSF |
| Start of Operation | 1984 |
| Operational Construction Method | Centre Line Earth Wall |
| Current Deposition Method | Decharacterisation of the TSF in progress |
| Target Annual Deposition Rate | Decharacterisation of the TSF in progress |
| Current Tailings Volume | 9.4Mm3 |
| Design/License Capacity – Volume/Tonnage | 9.4Mm3 |
| Crest Elevation | Main Wall – 816mamsl Saddle Wall – 816mamsl |
| Spillway Elevation | 814.33mamsl |
| Maximum Height | Main Wall – 84m Saddle Wall – 13m |
| Outer Wall Profile | 1V : 2.5H (Main Wall) 1V : 2.0H (Saddle Wall) |
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 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 qualitative bowtie method), potential failure modes along with their susceptibility and consequences, andthe control and mitigation measures.
From this process, nine risks were mapped that could in theory lead to a reduction in the dam’s structural performance, with one risk 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 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 also the risk assessment consequence definition and the mitigation measures to be implemented.
For the CDS II TSF the Self-rescue Zone was mapped out for a distance of 10km as 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 II TSF is shown in the tables below.
Areas affected by Impact Zone
CDS II TSF
| Municipalities in ZAS | Santa Bárbara & Catas Altas & Barões de Cocais |
| Municipalities in ZSS | Santa Bárbara & Barões de Cocais |
| Main Watercourses Impacted | Rio Conceição, Ribeirão Caraça & Rio Santa Bárbara |
| Watersheds | Rio Doce |
| Areas with Potential for Interference | Private properties; UHE Peti (owned by CEMIG); road infrastructure |
Summary of the socio-territorial characterisation of the impact zone
| Type of Property | Quantity |
|---|---|
| Occupied Houses | 385 |
| Summer Houses | 19 |
| Houses without a resident | 37 |
| Houses under Construction | 29 |
| Abandoned Houses | 3 |
| Establishment | 42 |
| Public Equipment | 6 |
| Public Equipment under Construction | 1 |
| Establishment under Construction | 1 |
| Closed Establishment | 3 |
| Entity | 3 |
| Rural Property | 6 |
| Institution | 4 |
| Plot with Improvement | 7 |
| Plot without House | 49 |
| Total Population in ZAS | 1,822 |
| Population with mobility difficulties | 132 |
| Population with Special Needs | 108 |
| Number of Sensitive buildings in ZAS | 30 |
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 that 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 II 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.
No material findings have been made in relation to the environmental and social monitoring programme.
An easily accessible and effective grievance mechanism has been implemented and will continue to operate 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 the community, was documented as having been undertaken in June 2023. 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, safety recommendations for the population, among other self-preservation information.
A copy of the CDS II EPRP can be downloaded on the following link: BARRAGEM CDS II – 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 II 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”).
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, all-in 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.
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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 of this document 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.