Collapse in Chambishi — tailings failure is a canary in Zambia’s Copperbelt

4 Mar 2025

The underlying conditions that allowed this disaster – weak regulation, limited enforcement capacity and Zambia’s heavy reliance on mining revenues – remain largely intact.

On Tuesday, 18 February a catastrophic failure occurred at Sino Metals’ tailings dam in Chambishi, Zambia, releasing more than 50 million litres of acidic effluent into the Mwambashi River.

The spill cut through farmland, poisoned livestock and contaminated one of the region’s most critical water sources, shutting down supply to roughly 500,000 residents in Kitwe, with further impacts on Kalulushi and Mpongwe.

A tailings dam is typically an earth-fill embankment dam used to store byproducts of mining operations after separating the ore from the unwanted minerals or rock material that are mined along with the valuable ore but have no commercial value.

The disaster is not an isolated event, but one on a growing list of tailings dam failures around the world, underscoring ongoing concerns about how mining waste is managed, especially in countries heavily reliant on mining investment.

“There are two phases to this disaster,” writer and conservation journalist Adam Welz told Daily Maverick. “There’s the immediate catastrophic impacts; dead fish, ground water contamination… but there are going to be very serious ecological effects of acidic, toxic waste.”

In Zambia, the collapse at Chambishi highlights broader systemic risks – underfunded regulatory enforcement, limited oversight and economic dependence on copper leaves environmental protections vulnerable to political compromise.

What happened at Chambishi?

Sino Metals Leach Zambia, a subsidiary of China Nonferrous Metal Mining (Group), has operated the Chambishi Leach Plant since 2006, initially reprocessing copper from waste dumps and stockpiles inherited from earlier mining operations.

In 2017, Sino Metals expanded its footprint with the development of the Mwambashi Mine, designed to provide fresh ore directly to the leach plant. With an investment of about $70-million, the mine aimed to produce 10,000 tonnes of copper cathodes annually.

Like all mining operations, copper extraction at Chambishi produces large quantities of waste known as tailings – a slurry of finely ground rock, chemical residues and acidic process water.

These tailings are stored in a tailings storage facility (TSF), a containment dam designed to hold the waste securely. When properly maintained, TSFs prevent environmental harm. When neglected, they become high-risk sites prone to catastrophic failure.

Warnings ignored?

Chambishi’s TSF failure has roots in the troubled history of waste management in the Copperbelt, including the old Musakashi Tailings Facility, which is part of the larger Chambishi waste complex.

A 2014 auditor-general report identified systemic mismanagement at multiple Copperbelt tailings facilities, including illegal artisanal mining at hazardous sites, uncontrolled effluent leaks, lack of signage and weak regulatory enforcement by the Zambian Environmental Management Agency (Zema).

Despite these warnings, Sino Metals built a new TSF in 2019 to accommodate increased production at Chambishi Leach Plant.

Instead of building entirely new and properly engineered infrastructure, Sino Metals followed the well-worn path taken by its sister company, NFCA Africa Mining, years earlier, and simply raised the wall of the old Musakashi dam to increase its capacity.

NFCA itself admitted in its annual report that the expansion did not fully meet safety and environmental protection requirements.

By 2022, further expansions followed under pressure to meet rising production targets. All of this happened despite a 2017 borehole study conducted by Copperbelt University, which confirmed groundwater near Sino Metals’ tailings facilities was already contaminated. The risks were documented, with a possible failure predictable – but it wasn’t prevented.

The collapse – fish wiped out

The failure at Chambishi fits a pattern seen in tailings disasters globally, according to analyses of satellite images and TSF engineers in Zambia.

Internal erosion – known as piping – developed through a divisional wall between two upper compartments of the facility.

Gradually, this erosion weakened the structure until the wall collapsed, sending water and tailings into a lower, inactive compartment. That lower compartment lacked adequate buffer space meant to absorb surges and quickly overtopped. The resulting cascade eventually breached the outer containment wall, releasing more than 50 million litres of acidic waste into the Mwambashi River.

The immediate consequences were severe, with the executive director of Zambia’s Centre for Environment Justice (CEJ) saying that “this disaster has caused unprecedented contamination, with pH levels between 1.8 and 3.5, endangering human lives, aquatic ecosystems and livestock that depend on these water sources”, confirming the extreme acidity of the discharge.

Local fish populations were wiped out, maize crops were contaminated and residents across Kitwe, Kalulushi and Mpongwe were left without safe drinking water. Daily Maverick has seen video footage purported to be from more than 200km away from the failure showing local fish floating dead on the river.

The link between Chambishi and Kitwe’s water crisis was direct and immediate. The Mwambashi feeds into the Kafue River, which supplies Kitwe – meaning that a failure at a single mine rapidly escalated into an urban water security emergency.

Public apology, but no accountability

In the aftermath of the failure Sino Metals chairperson Zhang Peiwen issued a public apology, saying: “This will never occur again, and we sincerely apologise to President Hichilema and the people of Zambia for the spillage of acids into major water sources.”

Sino Metals also promised compensation to affected farmers and committed to supporting water distribution efforts until safe supply could be restored. Mines Minister Paul Kabuswe and Copperbelt Minister Elisha Matambo visited affected residents, pledging tighter oversight and stronger regulatory enforcement.

Video footage seen by Daily Maverick shows Sino Metals employees dumping lime by shovel into the Mwambashi River in an attempt to mitigate some of the damage, to limited effect, considering that the contaminated water was already hundreds of kilometres downstream.

Welz says people try to downplay long-term effects that often aren’t recognised immediately – noting that the rehabilitative efforts seen so far do not appear to be systemically effective, but rather a symbolic act.

This response follows a familiar pattern in Zambia, where high-profile environmental disasters linked to mining are met with short-term political attention, public apologies and temporary relief measures, but rarely with structural reform.

The underlying conditions that allowed this disaster – weak regulation, limited enforcement capacity and Zambia’s heavy reliance on mining revenues – remain largely intact.

A response to detailed questions put to Sino Metals had not been received by the time of publication.

Regulatory blind spots

Zambia’s copper-dependent economy places Zema, the environmental regulator, in a conflicted position. Chronically underfunded, Zema relies in part on fees paid by the very companies it regulates, compromising its independence and limiting its capacity to conduct proactive inspections or enforce safety requirements.

That conflict is amplified in Chambishi because the mine operates within the Zambia-China Economic and Trade Cooperation Zone (ZCCZ – Africa’s first Chinese-funded special economic zone, or SEZ).

SEZs like ZCCZ were designed to attract foreign investment through tax holidays, customs exemptions and streamlined approvals, including environmental clearances. The very framework meant to attract Chinese investment helped shield Sino Metals from meaningful environmental oversight.

This isn’t the first time Chambishi’s operators have fallen foul of regulators. In 2013, Zema temporarily shut down Chambishi Copper Smelter for excessive emissions. In 2014, farmers won a lawsuit against NFCA after Musakashi’s tailings poisoned the stream and destroyed crops. Zema ordered tighter control, but inspections waned and fines appear to have been minimal.

On paper, SEZ developers like China Nonferrous Metal Mining (CNMC) are responsible for ensuring adequate infrastructure, including waste treatment and water protection. In practice, these obligations were either ignored or quietly waived as production pressures mounted.

Sino-Zambian pact: a deeper dependency

The Chambishi collapse is also a symptom of Zambia’s broader economic vulnerabilities. Following its 2020 sovereign default and the protracted 2021 debt restructuring deal with the IMF, Zambia has leaned heavily on Chinese investment to sustain its copper sector. Sino Metals, through its parent company, CNMC, has become a cornerstone of Zambia’s economic strategy.

That reliance has consequences. Zambian authorities are reluctant to enforce regulations too strongly, fearing investment withdrawal. This gives companies like Sino Metals the latitude to prioritise production over precaution.

This dynamic exists in part because China itself holds its domestic mines to increasingly strict environmental standards while turning a blind eye to the behaviour of its companies abroad.

China’s own green mining laws do not apply overseas, leaving it up to host countries like Zambia to enforce standards. In a weak regulatory environment like the Copperbelt, that oversight gap is quickly exploited.

Humanitarian disaster

The Centre for Environment Justice has framed the Chambishi disaster as more than just an environmental failure, but rather as a fundamental violation of human rights.

Zambia’s constitution guarantees the right to clean water, food security and a healthy environment, yet all three were compromised in the wake of the spill.

“This is no longer just an environmental disaster, it’s a human rights crisis rooted in the deep structural exploitation of our people and our land,” continued CEJ executive director Maggie Mapalo Mwape.

Whether Chambishi becomes a turning point or just another entry in Zambia’s long history of mining-linked environmental failures will depend entirely on what happens next.

Immediate compensation and short-term mitigation efforts, while necessary, are not enough. There must be a full, independent investigation into the causes of the failure, with findings made public and culpability clearly assigned. Affected farmers and residents deserve transparent compensation, not only for immediate losses but also for the long-term impacts on their land and livelihoods.

Zema itself needs urgent reform. Its funding should be independent of the mining industry, and its inspection and enforcement powers should be strengthened in law. Zambia should also adopt mandatory compliance with the ICMM Global Standard on Tailings Management, embedding international best practice directly into its Mining Act.

Without these reforms, Chambishi will not be the last disaster. The copperbelt is filled with ageing, poorly managed tailings dams, each one a warning waiting to be ignored. DM

Additional reporting by Ed Stoddard.

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