Czechia's Last Coal Mine Begins Backfilling: Sealing Four Shafts at ČSM Will Take Two Years

The OKD company has begun backfilling the ČSM mine in the village of Stonava in the Karviná region — the last operating coal mine in Czechia, where extraction ceased this past February. The work of filling four shafts with rock, the deepest of which plunges nearly a kilometre underground, will take about two years to complete.

According to OKD, backfilling the kilometre-deep shaft alone will require 45,000 cubic metres of waste rock, which the company had been stockpiling since the days of active mining as a byproduct of its processing plant. "We'll be sealing the shaft, roughly 900 metres deep, with certified stone of the right specifications, which we produced ourselves during the mining process," said David Hájek, director of production wind-down and mine manager.

The process follows strict safety protocols: powerful magnets have been installed above the conveyor belts to catch metal objects, since falling rock could otherwise cause sparks. The material is also sifted, with a maximum permitted fragment size of 100 millimetres. "The rock has to be laid down gradually so that no arches with hollow spaces form underneath — otherwise the fill could suddenly subside," Hájek explained. The process is monitored through a special backfill pipeline.

The conveyor belts carrying rock now run around the clock: the steady flow of material helps keep air circulating within the shaft, preventing methane from building up. Vladimír Polášek, head of OKD's transport division, explained that a certain amount of rock must continuously fall into the shaft to keep it properly ventilated. If backfilling has to be paused for an extended period, the shaft will need to be thoroughly checked using a special device with sensors that measure mine air composition before work can resume.

Before the backfilling began, OKD specialists sealed off hundreds of kilometres of underground tunnels, and pipelines for collecting mine gas, including methane, have already been installed in some of the shafts. According to OKD CEO Martin Djanaj, a cogeneration unit is currently being installed at the "North" site to generate electricity and heat from mine gas — it's set to enter test operation in October. Once the mine's technical decommissioning is complete, this energy will cover most of the company's needs, significantly cutting the cost of buying electricity from outside sources.

All equipment that could be profitably sold or reused has already been brought to the surface. "We drained and removed all oil fluids, dismantled nearly 90 kilometres of cable destined for scrap metal, and hauled out drives, electric motors, and both mining and tunnelling machines," Hájek listed.

Vladimír Polášek has spent his entire career in mine transport and will likely be overseeing the shaft closures for another two years. "When I start thinking about it, it's not a pleasant feeling. But a person has to be realistic and not take things too much to heart. The mine isn't being closed for no reason — I believe in those reasons, and there's no point dwelling on it constantly," he admitted.

Once the four shafts are sealed, demolition of the surface structures will begin. As part of restoring the surrounding landscape, OKD will also monitor for possible ground subsidence.

The company, state-owned through Prisko, has set aside a reserve of 3.3 billion crowns for the ČSM mine's closure. "We're running slightly ahead of schedule, and we're saving noticeably compared to the cost projections — so far, everything's going well," Hájek noted.

Coal extraction at the ČSM mine stopped in early February this year, marking the end of the last operating hard coal mine in Czechia. Over recent decades, OKD has gradually shut down all its mines as extraction stopped being economically viable. The company is now shifting its business focus: alongside using mine gas, it's moving into property development. OKD currently has around 550 permanent employees, some of whom will be gradually laid off by the end of the year as various stages of the mine's closure are completed.

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Around Prague, based on reporting by ct24.ceskatelevize.cz