2023 – Climate Change Resilience Assessments for Tailings Storage Facilities

Leila Ang, Nigel Moon

Existing and planned Tailings Storage Facilities (TSF) are being subjected to evolving standards to satisfy as low as reasonably practicable (ALARP) principles in design, construction, operation, and closure. As a minimum in Australia, TSF designs are led by the Australian National Committee on Large Dams (ANCOLD) guidelines; however, the Global Industry Standard on Tailings Management (GISTM) is the current benchmark for TSF management practice worldwide. Many mining companies are currently undertaking GISTM compliance studies to demonstrate to stakeholders that identified TSF risks are being managed proactively and mitigations are in place at appropriate TSF life cycle stages. Consideration of climate change is an explicit requirement in GISTM, whereas this consideration is a gap in the current version of ANCOLD guidelines. As a result, Australian-based TSF practitioners resort to using the prescriptive guidance featured in the Australian Rainfall and Runoff Guide to Flood Estimation and other literature based methodologies alongside GISTM.

TSF risk assessments generally consider baseline climate for broader failure mechanisms such as slope instability, piping erosion/seepage and overtopping; however, global experience is showing the impact of climate change can potentially result in TSF failure. Therefore, alternative failure pathways due to climate change are created relative to conventional expectations. These risk types can be identified in varying time horizons from end of operations to closure stages, whilst noting the inherent uncertainties in future climate projections. The risk severity range can be inferred from selected climate change scenarios to provide representation of the potential future conditions and the level of resilience for the TSF can be broadly determined.

TSFs will likely experience chronic and catastrophic impacts due to climate change. Water, which is both an asset and risk, is vulnerable to climate change. For instance, inflow design floods may be exceeded due to intensified hydrologic events. Therefore, climate-proof hydrologic predictions for design of TSFs is essential to increasing resilience in the future. Chronic impacts such as changed geochemistry due to increased wetting and drying cycles and/or unsuccessful rehabilitation due to increased drought conditions and evapotranspiration can also introduce financial risk.

This paper provides an overview of a recent case study where climate change considerations were included in a TSF resilience assessment. Consideration of climate change impacts and hazards lead to more resilient TSF design, management, and overall stewardship.