How to Design a Tailing’s Dam Full Removal? Lessons Learned from a Case Study in Brazil

December 16, 2024

Following the catastrophic mining dam failures in Mariana (2015) and Brumadinho (2019), Brazil enforced stricter legislation on mining dams, including the prohibition of upstream raising construction methods and the mandatory decommissioning and decharacterization of existing upstream-raised dams as stipulated in ANM Resolution No. 13/2019. This case study presents the decharacterization project of a high-priority dam featuring two pits and a reservoir, initially holding approximately 2,000,000 m³ of tailings. The project involved extensive trade-off studies, geotechnical and hydrogeological assessments, and pilot testing to identify the optimal decharacterization approach.

The selected solution, involving the complete removal of upstream tailings and the creation of a uniform flat slope with a central channel over the starter dam, was chosen for its reduced consequence classification and potential for tailings reuse. The project was divided into multiple phases, with each phase addressing specific challenges and leveraging remote excavation technology. Detailed investigations and pilot tests provided critical insights, leading to phased excavation and continuous model refinement. During the design and governance review process, the final design outcome was modified from a decommissioned starter dam to complete removal of the embankment and tailings, and restoration of the original valley.

Key challenges included remote investigation and excavation, tailings variability, 3D modeling complexity, stakeholder engagement, and stringent water management requirements. The project’s iterative design approach, underpinned by robust stakeholder engagement and advanced modeling techniques, facilitated successful decharacterization while ensuring safety and compliance with regulatory standards. Lessons learned emphasize the importance of early and continuous stakeholder involvement, iterative design processes, the observational method, and the critical role of hydrogeological and deformation models in managing complex decharacterization projects.

Junior, B., C. Rodrigues, N. Singh and L. Souza. 2024. “How to Design a Tailing’s Dam Full Removal? Lessons Learned from a Case Study in Brazil,” in Proceedings of the Tailings and Mine Waste Conference, 10-13 November 2024. Colorado, USA.