Added 29 May 2024 by Gem Ellithorn
A Tailing dam is a large structure, with walls typically built from earth, clay, and rock to form a large pond or lake.
They are used for storing waste liquids left over from leach mining processes. Leach mining involves the use of chemicals
to dissolve elements like copper, gold, and uranium from the rocks containing them.
After separating the valuable minerals
from the liquid chemicals, the remaining solution is called tailings, these need to be stored for later processing.
Environmental Concerns
Tailings often contain toxic chemicals, and heavy metals, and can sometimes be radioactive depending on the type of mining. If not properly contained, these contaminants can leak into the surrounding environment, polluting water sources and harming wildlife.
Dam Construction
Tailing dams are typically built like embankment/earthen dams, using earth, clay, and rock to form a wall that holds back the tailings. Tailing dam failures can be catastrophic. If a dam breaks or leaks, it can unleash a massive wave of toxic sludge that can devastate entire communities. These failures can be caused by structural weaknesses, heavy rains, or earthquakes, and structural weakness brought about by unknown leakage.
A brief web search will show that in the last 14 years alone, 57 tailing dam failures have occurred worldwide. These failures are not just an environmental concern; they can claim lives. In the same period, 549 people were killed by failed tailings dams, and hundreds of thousands more have been left without homes, farms, clean water, and food
(reference: https://www.wise-uranium.org/mdaf.html).
The Upstream Method?
When it comes to the construction of a tailing dam the most common way is the upstream method, this is where you have a starter dam this will usually be a small and stable embankment made of earth and rock. This initial embankment forms the foundation for the growing tailing dam. Liquid tailings are then emptied from the upstream side of the
starter dam.
These tailings settle and solidify over time, forming a beach-like area next to the dam wall. As the tailings accrue and the beach area solidifies, the dam wall itself slowly rises, any additional earth and rock materials are placed on top, extending it further upstream this is why it’s called “Upstream method.”
While this method seems economical… it comes with a significant risk. Studies show that over 32% of tailing dam failures in recent years were linked to the upstream construction method. Upstream dams are more likely to have weak spots in the ground that can turn to mush and slurry under pressure or shaking (like from earthquakes).
Dam Design, Construction and Management
The way tailings dams are often built means they can trap water pressure underneath; this can turn soil into a liquid under certain conditions. In addition, all methods of constructing dams are susceptible to overtopping if not professionally designed or maintained. When a dam failed in South Africa in 2022 it caused widespread destruction. This tragedy emphasises the urgent need for stricter regulations and improved safety measures in tailing dam design, construction, and management.
Another example is the dam failure in Brazil in 2019, which unleashed a wave of toxic mud that buried the communities surrounding it. These massive structures pose a significant threat to the environment and human life when they fail.
Dam foundation problems often stem from two things:
- Building over weak geology.
- Natural events (extreme weather and earthquakes).
The following study "Root Causes of Tailings Dam Overtopping: The Economics of Risk Consequence”
(by Bowker, L.N., Chambers and 09/2016) which examines historical tailings dam failures. This study highlights the maintenance risk factor, whereby a lack of ongoing monitoring and maintenance can lead to dam failure.
Advanced Monitoring Solutions
Unfortunately, traditional inspection methods for tailing dams often have limitations. These inspections might not be often enough to capture leaks before they get accelerate allowing problems to develop undetected.
Sensor recommends the use leak monitoring in tailing dam design. SENSOR DDS® technology can provide continuous, or intermittent monitoring of the dam allowing fast detection of possible leaks.
The potential impact of tailing dam failure demands an educated approach involving the design, technology, careful construction, and regular maintenance. Applying advanced monitoring technologies like Sensor DDS® can play a crucial role in preventing future disasters, reducing clean-up costs, whilst safeguarding lives and protecting local environments.
Further Reading Material:
Piciullo, L., Storrøsten, E.B., Liu, Z., Nadim, F. and Lacasse, S. (2022). A new look at the statistics of tailings dam failures. Engineering Geology, 303, p.106657. doi:https://doi.org/10.1016/j.engg...
www.wise-uranium.org. (2024). Chronology of Major Tailings Dam Failures. [online]
Available at: https://www.wise-uranium.org/m... [Accessed May 7 2024].
Vale Dam disaster: $7bn Compensation for Disaster Victims. (2021). BBC News. [online] 4 Jan.
Available at: https://www.bbc.co.uk/news/bus... [Accessed 7 May 2024].
Nassivera, J. (2018). Dam Failures: Common Reasons For Complications. [online] interestingengineering.com.
Available at: https://interestingengineering... [Accessed 7 May 2024].
Bowker, L.N., Chambers, D.M. and Colorado State University. Department of Engineering, P. (2016). Root Causes of Tailings Dam overtopping: the Economics of Risk & Consequence. [online] mountainscholar.org. Colorado State University. Libraries.
Available at: https://mountainscholar.org/it... [Accessed 7 May 2024].