This story was originally posted by The Conversation
Mining is essential to modern lifestyles. Copper, iron and other mined products are vital to the products many people take for granted, like electronic devices. Being able to buy these goods quite easily may give a person a false sense of how difficult it is to extract the elements they’re made of.
Mining involves the removal of mineral-rich rock from the ground and processing it to extract the high-value minerals. Depending on the mineral, this quantity can be as low as a few grams in a tonne of rock.
For example, removing a tiny quantity of platinum from rock requires finely grinding the rock. The fine material that remains once the platinum is removed is known as tailings.
Every mining operation produces tailings. This can be coarse, like instant coffee granules, or fine, like cocoa powder. Tailings are typically mixed with water to form a liquid slurry that can be pumped and transported easily.
Slurry is kept in specially designed tailings dams. The designs are unique and depend on what is being mined and the local area.
Unfortunately, the history of mining is stained with examples of poorly managed dams that collapse, spilling the slurry, which is sometimes toxic. This can cause serious environmental, social and economic damage.
One such mine disaster happened in February 2025 in Zambia at the Sino-Metals Leach Zambia copper mine. Over 50 million litres of toxic waste flowed over the dam’s wall into the Mwambashi River. From there it flowed into one of the largest and longest Zambian rivers, the Kafue.
The pollution travelled further than 100km from the dam, contaminating the river, and killing fish and livestock on nearby farms. The Zambian government had to shut down municipal water to the city of Kitwe to protect residents from consuming the polluted water.
This should not have happened, because steps have been taken to ensure proactive management of dams. In 2020, the Global Industry Standard on Tailings Management introduced a new set of safety measures and standards.
Many mines are proactively embracing these standards. This enhances community trust in tailings dams. But other mines are not engaging with communities that might be affected by dams. Or communities may feel unsure what to ask the mines.
We are geotechnical engineers who have studied tailings dam collapses. Here, we outline six questions people living near mines should ask mine management to ensure they understand the key hazards and risks in their communities.
Old dam tailing
1. How far will the slurry flow?
Each tailings dam has a zone of influence. This is determined by analysing what would happen if the slurry breached the dam walls and started to flow out. It is an estimate of the area which would be swamped by tailings if the dam failed.
Generally, tailings disasters have caused significant damage up to a distance of 5km from the dam. If the tailings slurry gets into a river, it can flow hundreds of kilometres downstream.
Read more: Burst mining dam in South Africa: what must be done to prevent another disaster
Zones of influence are often determined for extreme events, like once in a lifetime storms or large earthquakes. But zones of influence could also include places affected by dust or water pollution from the mine.
If you can see a tailings dam from where you live or work you should consider yourself within the zone of influence.
2. Who is responsible for the dam?
Clearly defined roles and responsibilities for day-to-day operation should be in place in every mine. There should be suitably qualified engineers appointed to carry out monitoring and maintenance of the dam. There need to be enough qualified people to cope with the size of the dam.
The management structure should set out how day-to-day issues related to the tailings dam are discussed between workers on the ground in mines and top management, and how solutions are found. Mines should also keep audit and inspection reports on their tailings dams, and records should be kept over the long term (because tailings dams are often operational for several decades).
3. What about the environment?
Mines should have plans to reduce the impact that tailings dams have on the environment. These would have been informed by public participation. The plans must state what monitoring is in place to measure the impacts of dust and water (groundwater and surface water).
The true extent of impacts only becomes apparent once the mine starts operating. So, the public should hold mines accountable for commitments made. Mines should satisfy communities that monitoring is continuing to identify and track the dam’s environmental impacts.
Closure plans should also be continuously communicated to mining-affected communities. This will assure the community that when the miners leave, they won’t be left with a dangerous dam near their homes, with no one to look after it.
4. Will the tailings dam be safe when it rains?
A common way that tailings dams fail is when water or slurry washes over the dam sidewalls. This washes away the support. It is known as overtopping, and can happen in storms or if too much tailing is pumped into the dam.
Overtopping is best managed by keeping the water a certain distance below the dam wall. Mine management must measure this regularly and control how much tailing they pump to the dam. Their task is to make sure that even in a severe storm the level will stay well below the top of the dam wall.
5. Has the dam always behaved as expected?
Small failure incidents such as sloughs, slides and bulges where dam walls move but no slurry is released can occur. Mines should investigate and report these, detailing likely causes and mitigation measures implemented.
Publicly available satellite imagery can easily show where mine tailings dams are becoming unstable. Mines should be transparent and provide explanations for these to avoid any speculation over whether the dam is stable or not.
6. What alterations have been made?
Sometimes dams must be changed to accommodate changes in mining or the extraction process. These changes could include how fast the dam is being built, moving the position of the dam wall, or placing material at the base of the wall to stabilise it.
The unexpected consequences of alterations to a tailings dam could be water seeping out and creating damp spots, leading to dam walls sagging or cracking. If left unchecked this can lead to structural failure.
When substantial changes are made to a dam’s design, mines need to demonstrate that sufficient consideration has gone into making these changes.
