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Calcinados TSF, Brazil
At 10 April 2024
Coordinates: Lat. 6.219122°, Long. -1.665141°
Guidance Note
Refer to our guidance note.
Description and Lifecycle Design
Constructed in 1986, the Calcinados TSF has a crest elevation of 863 m, a maximum height of 57m and a crest length of 315m. Seepage collected at the dam toe is pumped back into the TSF. The dam was constructed with two starter dams which were subsequently raised with the coarse fraction from cyclone tailings to provide internal drainage for the dam. This was in addition to the blanket drain at the base of the dam.
There was a penstock inside the TSF with a pipe crossing the dam. The outlet has since been covered by the rockfill buttress. The rockfill buttress along the lower portion of the dam is composed primarily of schist rock with a relatively high fine content compared to run-of mine-material.
The Saddle Dam separates the Calcinados TSF with the Rapaunha TSF. It has a crest elevation of 863m (same as the Calcinados Dam), a maximum height of 6m, a crest length of about 15m, and slopes of 2H:1V on both the downstream and upstream sides. This TSF has a spillway that was constructed as part of the saddle wall raise carried out in 2017. This spillway overflows into the adjacent Rapaunha dam. The basin of the TSF was lined with an HDPE liner in 2023 to minimise the ingress of rainwater during the rainy season as the TSF is not currently operational.
Calcine TSF General Information
| Facility Name | Calcine TSF |
| Start of Operation | 1986 |
| Construction Method | Downstream cyclone wall |
| Current Deposition Method | Deposition of filtered tailings to meet the closure design. |
| Target Annual Deposition Rate | 180,000m3/a (Queiroz production when in full operation), currently plant is not operating |
| Current Tailings Volume | 4.4 Mm3 |
| Design/License Capacity – Volume/Tonnage | 4.4 Mm3 |
| Crest Elevation | 863 mamsl |
| Spillway Elevation | 862 mamsl |
| Maximum Height | 57m |
| Outer Wall Profile | 1V:2H (Downstream) |
Consequence Classification
| TSF Classification | GISTM: 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 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 FMEA method), potential failure modes along with their susceptibility and consequences, and the control and mitigation measures.
From this process, 10 risks were mapped that could in theory lead to a reduction in the dam’s structural performance, with one of these risks being classified as unacceptable, five in the ALARP (manageable) range and four in the acceptable range.
Since the unacceptable risk was associated with material properties that are susceptible to liquefaction, in accordance with Brazilian Legislation – Art 52 of ANM Resolution No. 95/2022, the operator (AGA) is required to immediately stop releasing tailings onto the TSF and maintain monitoring, maintenance and conservation of the TSF until it is reclassified to the ALARP (manageable) or acceptable level. AGA has stopped the release of pulp and filtered waste to the Calcine TSF and is proposing actions that increase the level of confidence in the structure so that the decharacterisation works continue with the lowest possible risks.
Due to uncertainties in certain material parameters, a geotechnical investigation and design to remediate this condition was initiated in 2023. Geotechnical investigations, finalised in February 2024, indicate that the TSF in fact meets the minimum requirements for the post liquefaction safety factor and therefore no remedial measures are required. The decharacterisation design for this facility will now be carried out based on the new geotechnical information.
For the five risks in the ALARP (manageable) range, action plans have been developed to, where possible, further reduce these risks 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.
The impact zone covers a distance of 84.7km downstream of the Calcine TSF. 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 Calcinados TSF is shown in the tables below.
Areas affected by Impact Zone:
Calcinados TSF
| Municipalities in ZAS | Nova Lima (MG), Raposos (MG) |
| Municipalities in ZSS | Nova Lima (MG), Raposos (MG), Sabará (MG), Belo Horizonte (MG), Santa Luzia (MG) |
| Main Watercourses Impacted | Rio das Velhas, Córrego da Mina (Queiroz), Ribeirão Sabará, Ribeirão Arrudas, Ribeirão da Prata, Córrego Malheiros, Ribeirão Baronesa, Ribeirão da Mata, Rio Taquaraçu |
| Watersheds | Rio das Velhas |
| Areas with Potential for Interference | Private properties, road infrastructure (MG-030, AMG-150, MG 437, MG-262, BR-381, AMG-145 and MG-020), streets, bridges, in addition to commercial & healthcare establishments, schools, inns, police stations, museums and historical heritage referring to the district of Honório Bicalho in Nova Lima (MG), and to the urban area centers of Raposos (MG), Sabará (MG), Santa Luzia (MG) & Lagoa Santa (MG). |
Summary of the socio-territorial characterization of the impact zone
| Type of Property | Quantity |
|---|---|
| Occupied Houses | 1,370 |
| Summer Houses | 26 |
| Houses without a resident | 165 |
| Houses under Construction | 116 |
| Abandoned Houses | 24 |
| Establishment | 275 |
| Public Equipment | 31 |
| Demolished Houses | 12 |
| Establishment under Construction | 9 |
| Closed Establishment | 56 |
| Plot with Improvement | 60 |
| Plot without House | 131 |
| Total Population in ZAS | 3,079 |
| Population with mobility difficulties | 289 |
| Population with Special Needs | 151 |
| Number of Sensitive buildings in ZAS | 20 |
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 – typically quarterly and Annual Performance Reviews
- Independent Tailings Review Board (ITRB) 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 | April 2023 | October 2024 |
| DSR | NA | 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.
Summary of Material Findings and Mitigation Measures:
| Reference | Material Finding | Mitigation Measures to Meet ALARP |
|---|---|---|
| 2023 Risk Assessment | Low safety factors at the Main Wall | No Deposition of tailings on the TSF. Extensive Geotechnical Investigation Campaign. Design of TSF decharacterisation to meet stability requirements. |
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 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 fitted on emergency vehicles 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 and were developed based on the zone of influence, in which a maximum walking distance of 1,000m was considered in order to allow a quick and safe route to meeting points. The meeting point signage has information such as telephone numbers of emergency agencies, recommendations for the population, among other self-preservation information.
A copy of the Calcinados EPRP can be downloaded on the following link: BARRAGEM CALCINADOS – 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 Calcinados 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.