Regulating a mine is crucial – also when its ore production stops. Each year, hundreds of mines around the world reach the end of their operational life. In developing countries mines are often abandoned and left to deteriorate, leading to serious environmental challenges. Meanwhile, unused mines in developed parts of the world such as the US and Canada begin a long road of planned remediation to help reduce their ecological impact.

There are millions (yes, millions) of old, abandoned mines honeycombing the globe today, and hundreds of thousands of these pose a threat to the environment and to human life. In the US alone there are well over half a million; including at least 100,000 classified as a serious environmental risk. Australia has identified more than 50,000, and Canada over 10,000 (source: Geneva Graduate Institute). For most countries, the true number of orphaned mines is a mystery.

When operations stop, responsibilities don’t

Mining is inherently a finite activity, making it essential to plan for closure from the outset. While approaches vary, there are still cases where closure and post-closure monitoring strategies are not fully developed or implemented, highlighting the need for more consistent long-term planning across the industry.

A document from the National Mining Agency (ANM) recently obtained by Reuters revealed that Brazil has around 4000 mining sites showing signs of abandonment, a whopping 11% chunk of all Brazilian mines, and that there is insufficient oversight at recognizing or managing their risks. Despite the environmental catastrophes caused by mining regularly making international headlines, what is less well-known is that a mine that has reached the end of its productive life has the potential to cause similarly dire consequences if left unattended.

Buried dangers beneath the surface

Unsealed abandoned mines are extremely treacherous. In the US, many casualties have been reported as a result of hidden hazards (source: AP News). A multitude of geological risks include ground collapse, sudden sinkholes or slope instabilities near the mine site, air and water pollution (often from toxic gases or heavy metals like arsenic or lead), significant groundwater alteration and subsidence or uplift of the ground surface. All of these have caused loss of life and led to major ecological disruption.

The challenge of assigning responsibility

While achieving total oversight of millions of abandoned mines worldwide is nearly impossible, nations can still move in the right direction by assuming or delegating responsibility, allocating sufficient funds, and enacting surveillance legislation.

The US Environmental Protection Agency (EPA) has placed several hundred abandoned mines on its National Priorities Superfund List (NPL), its roster of the most polluted and hazardous places in the country demanding urgent cleanup. Disused mines like the Chevron Questa Mine in New Mexico are already benefitting from this government initiative. In Australia, several measures have been implemented to deal with abandoned mines, including a dedicated ‘Post-Closure Fund’ to meet the ongoing costs of managing declared mine land, and which also allows mines to responsibly relinquish land. A ‘Mine Land Rehabilitation Authority’ has been established specifically to monitor, maintain, and manage old mine sites (source: Minerals Council of Australia). Australia’s ‘Legacy Mines Program’ specifically targets orphaned mines which have no identifiable party responsible for them in order to prevent further degradation, remove contamination and support beneficial reuse. However, financial limitations remain a major hurdle for developing countries to follow suit.

Apart from dedicating funding, nations everywhere also need to double down on designing laws and standards governing all aspects of a mine closure strategy, so that the responsibility of maintaining unused mine sites is assigned appropriately and that their continued upkeep is properly carried out.

When closing a mine, monitoring strategy matters 

Governing bodies are urged to push mining companies to adopt regulations such as the ‘Global Industry Standard on Tailings Management’ (GISTM), which makes sustainable closure and post-closure strategies of mine tailings storage facilities (TSFs) a top priority. Since its creation, the standard has been working well in improving closure strategies.Adoption of GISTM into an improved mine closure strategy is currently in progress in West Africa, and has recently been widely adopted in several other regions including South Africa. 

However, it’s not enough to simply create new laws and legislation to deal with abandoned mines – they must also be effectively enforced.

Keeping watch on abandoned mines

It’s essential to keep a close eye on abandoned mines, but it’s clearly a huge challenge. Analog monitoring that relies on humans is expensive and unreliable, and can regularly put people in harm’s way. Even if companies install modern geological instruments, it’s pointless when those are poorly maintained or if the proper checks aren’t carried out.

Satellite monitoring data is helpful, but limited. The time it takes for a satellite to orbit restricts the transmission speed of critical information, and millimetric shifts cannot be easily detected. A sinkhole can appear in a matter of hours, which is much too quick for a satellite to pick up. Something state-of-the-art is needed, requiring minimal maintenance and extreme precision. This is where remote wireless monitoring sensors are proving to be incredibly valuable.

Remote monitoring: ready to deploy

Worldsensing’s wireless sensors are suitable for even the most inaccessible mining sites. Their Long Range (LoRa) radio communication extends to cover up to 15 km, or up to 10 km underground, thanks to a network of repeaters. Cables are not needed. The sensors perform even under extreme conditions ranging from -40 °C to 80 °C. This makes the monitoring system ideal for deployment in mining tunnels, ground excavations, waste dumps, open pit mines, tailings dams and every kind of complex subterranean topology.

Moreover, the sensors operate on an ultra-low-power protocol, enabling deployments to remain in place for as long as 10 years with zero need for maintenance. An important point for remote and unoperated mines. Since a millemetrically precise real-time data log is beamed continuously, automatically and directly to the people that matter, ground staff on site are not needed and can spend more time analyzing rather than collecting.

The IoT-based Worldsensing monitoring system enables a hands-off system via complete digitization of sensors including piezometers, in-place inclinometers, multi-point borehole extensometers (MPBX), GNSS, crack meters, weather stations, flow meters, load cells, and water quality probes. That means it’s possible to remotely monitor everything from groundwater levels, rainfall, and drain success to horizontal displacement, vertical deformation at different depths, surface crack activity, tension and remaining load in anchorages, and water quality. That’s an enormously rich trove of data that can be used to pick up almost any geohazard posed by an abandoned mine.

Living safely with abandoned mines

Abandoned mines are a permanent reality, and their numbers will only increase with time. Yet the dangers they pose don’t have to grow with them. With decisive action from mining companies and regulators, and the adoption of advanced tools like remote monitoring, we can keep constant watch, detect threats early, and act before small problems turn into disasters. The challenge is undeniable, but it is within our ability to manage it.