From conceptual design to progressive closure of a dry-stack in a high seismic and tropical setting: a case history

The Buriticá Gold Project is located in Antioquia, northern Colombia. Planning and design encompassed two years of fast-tracked pre-feasibility and feasibility studies, and stacking plan development. However, start-up and early operations were challenged by unanticipated differences in site climate and topographic setting, despite similar rainfall expectations. Changes in mine ownership and processing approaches, pandemic restrictions, minimal underground backfill availability due to social issues, restricted starter cell footprints, and filter plant start-up issues all converged to result in poor dewatering efficiency, high moisture and poor compaction control within the first cell of the tailings storage facility (TSF) in the first 6–12 months, and a steep learning curve for the operations and construction quality assurance teams. This paper presents a case study overview of the 2,500 tpd operation, summarising the pre and post-start-up observational method approach to both tailings characterisation, placement, handling and compaction specifications refinement, ongoing geotechnical monitoring and lessons from the progressive closure procedures and challenges of the actual versus originally conceived construction approaches for this project. Use of unique co-disposal, foundation excavation geometries and reinforcing design elements as well as tight moisture conditioning and compaction control are employed to overcome siting and footprint constraints, imposed height restrictions, low liner interface strengths and other challenges; while providing for global stability. Managing key risks, including designing for safe passage of potential probable maximum flood) flood and debris flow events on the adjacent Bermejal creek. Internal drainage and a double-liner with a leak detection system was installed to manage contact water and seepage. Progressive reclamation of the outer slopes supports non-contact water management, minimises air-entry and promotes vegetation growth and dust management – particularly for community access between isolated villages located upstream and downstream of the property. The success of the project is due not only to both diligently communicating and advocating for strict adherence to the original design intent through ownership and Engineer of Record (EoR) changes, but also allowing for flexibility in the observational approach and developing strong relationships and communication through the engineering, construction quality assurance and operations crews. The diligent shepherding of the project by in-country EoRs and Deputies, provide continuity to the project, allowing for transparent communication of the project challenges, risks and successes directly with communities and regulatory agencies; which has resulted in positive performance of the project, with expansions beyond the original approvals now being considered because of the demonstrated performance.