In recent years, northern Chile has experienced significant changes in its weather patterns, characterized by a higher frequency of extreme events, such as intense rainfall in traditionally arid areas. Although average rainfall in this region remains low compared to other areas of the country, there is concern about Whether mining areas are prepared to receive high-intensity rain, such as in Valencia on October 29, 2024.

Tailings infrastructure considers design parameters that include tolerances for 100- or 500-year rainfall events, meaning the facility is designed to withstand the heaviest rainfall. However, the mining industry faces new challenges from increased extreme rainfall caused by climate change.

According to a paper published in 2017 (Roche et al. 2017), increased climate variability and extreme weather events have not always been considered when designing and constructing existing tailings dams. Planning for an uncertain climate future is now essential to risk management. Heavy rainfall has been responsible for 25 percent of tailings dam failures globally and 35 percent in Europe (Rico et al. 2008). We cannot forget the case of Brazil, where two tailings dam disasters highlighted the vulnerability of these structures to extreme weather conditions. In 2015, the collapse of the Samarco dam in Mariana resulted in one of the worst environmental disasters in Brazilian history, releasing 62 million cubic meters of mining waste. In 2019, the Brumadinho dam tragically collapsed, killing more than 270 people. Both cases underline the urgent need to improve risk management at tailings dams to prevent future tragedies.

With climate change’s increasing uncertainty, tailings dam planning must consider seismic issues, the uncertainty of extreme rainfall, and associated risks.

Tailings facility planning and design must evolve to adapt to this reality. Proper tailings management and efficient water handling have become critical to ensure operational safety and minimize environmental risk. Tailings facility failures can cause irreversible ecological damage and pose a significant risk to mining companies’ reputation and economic viability.

This article examines the importance of anticipating these climate changes by evaluating the current tailings management practices. By optimizing tailings management strategies, it is possible to mitigate the impact of unusual rainfall and ensure the sustainability of mining operations.

EXAMPLE OF A HYPOTHETICAL CASE IN CHILE

If 500 mm of rain falls in Chile in 8 hours, as in Valencia (see Table 1), would the Chilean mining industry be prepared to receive this large volume of water in the tailings systems? If there were rains like those in Valencia, what would happen downstream of the tailings deposits?

The design should consider extreme weather conditions, but it must be verified if the final design considered rainfall intensity in a few hours, such as in Spain.

What should happen in operation?

Depending on the tailings deposit, much water can be stored up to a permitted operational limit. Above this operational limit are the flood limits where the water is stored. If the rain is more intense, flood evacuators discharge the water in a controlled manner downstream of the tailings deposit.

What tailings management practices should a mining company implement if extreme rainfall occurs?

For the tailings system to continue operating, the following preventive activities must be carried out:

• Verification of the walls.
•  Verify the waterproofing of the walls.
• Verification of the spillways.
• Maintain continuous cleaning of the contour channels.
• Verify the operation, function, and integrity of the contour channels.

CONCLUSION

Historical rainfall data is critical for performing water balance calculations, which assess the amount of water entering and leaving the tailings facility. This helps determine the size of storage ponds, seepage control measures, and the need for water treatment systems.

Engineers use intensity-duration frequency curves based on historical rainfall data to estimate the intensity and duration of rainfall events. These curves help design for extreme rainfall events that could cause tailings dams to overflow or structural failure. However, consideration should be given to whether extreme events that could occur due to climate change are considered.

In operation, it is key to maintain water diversion systems to manage stormwater caused by intense events. This ensures that the tailings dam is not overloaded during extreme rainfall, reducing erosion or overflow risk.

In conclusion, to ensure safety and efficiency in mining operations, it is essential to implement a rigorous approach to the verification of the walls and their waterproofing, as well as the maintenance and continuous monitoring of the contour channels. The stability and integrity of the tailings walls are critical components that must be regularly inspected to prevent leaks or structural failures. Likewise, the constant cleaning of the contour channels ensures adequate water flow, avoiding blockages that can generate overflows or erosion in the facilities. In addition, verifying the operation and correct functioning of the spillways guarantees the efficient evacuation of stormwater, minimizing risks in extreme weather conditions. These practices protect the facilities and the environment and strengthen the long-term sustainability of mining operations.

We have extensive experience in water management for tailings systems at Process Minerals Consulting. Our team can perform a detailed survey of your mining operation’s information to optimize the safety and efficiency of your processes. If you would like to know more about how we can assist you, please do not hesitate to contact us at info@processminerals.cl