Assessing the risk of failure of tailings storage facilities due to changes in hydroclimatic stressors in a warming world - Case study of Chile

Tailings storage facilities (TSFs) present a persistent stability challenge to the global mining industry, particularly given the large quantity of inactive, closed or abandoned deposits. Due to the potential for catastrophic failures, hydrometeorological hazards, such as extreme precipitation, are one of the main threats to these structures. This stems from the stress that infrastructure can undergo when dealing with these extreme events.  

Current design standards require that TSF be capable of handling the Probable Maximum Precipitation (PMP) and the associated Probable Maximum Flood (PMF). However, the reliability of these design values, traditionally derived from stationary statistical records, is increasingly uncertain in the context of global warming. 

Here, we assessed the hydrological failure hazard of four TSFs across significantly diverse climatic zones -ranging from arid to cold-humid climates- in Chile, a leading country in global copper production with nearly 800 TSF associated with these activities, most of which are inactive or abandoned. To do so, we first estimated PMP values over the historical period 1960-2014 using physically based hydrometeorological methods, including moisture and wind maximization, and contrasted these values with statistically obtained estimations typically used in consultancy. Secondly, to assess long-term safety, projected PMP values for the 21st century were calculated using data from four GCMs following SSP2-4.5, SSP3-7.0, and SSP5-8.5 climate projections with the same hydro-meteorological approach. Changes in the values of PMP throughout the century were analyzed through overlapping 30-year rolling windows over the period 2015-2100.  

Preliminary results for the historical period reveal marked methodological discrepancies between physically based hydrometeorological and statistical methods. For example, while moisture maximization yields estimated values closely aligned with statistical baselines, the incorporation of wind maximization drives PMP values significantly higher, surpassing other methods by up to 78%. Furthermore, no convergence of trends is observed among the four sites in the near future (2015-2044). However, consistent upward trajectory in PMP becomes evident by the century’s end. This is most pronounced under high-emission scenarios, where estimates for the 2075–2100 period rise by 24% to 81% relative to the historical baseline. 

Ultimately, these findings highlight that relying solely on historical statistics may significantly underestimate failure risks due to hydroclimatic extreme events. Ongoing efforts are focused on better understanding how changes in PMP propagate into PMF and how methodological decisions influence hydrological design.