Pyhäsalmi mine is the deepest one (1.4 km) in Europe. Photo: Tiia Monto / Flickr
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The Pyhäsalmi mine in central Finland, the deepest in Europe, will soon begin filling with water unless a delayed energy project receives immediate backing. Officials confirmed that decommissioning will proceed this autumn, likely ending over 60 years of mining and two decades of attempts to repurpose the vast underground site.
Mining operations in Pyhäsalmi ended in 2022 after zinc and copper reserves were exhausted. Since then, the site has been maintained dry in hopes of securing a major post-mining project.
The leading candidate, an underground pumped-storage hydroelectric plant, remains in limbo as its developer, Swedish firm SENS, has yet to finalise an investment decision.
The state committed over €25 million in support, but the window for action is closing. According to Sakari Nokela, development director of the local Callio initiative, there is little time left.
“Everything is still possible if a decision is made now. But I see that as very unlikely,” he said.
Without confirmation, the mine will begin flooding naturally once pumps are shut off later this year, as required by environmental permits.
Water will enter the tunnels from groundwater and surface runoff. According to the mine operator, the site currently pumps out around 600,000 cubic metres of water annually, equivalent to 600 million litres. That figure is expected to remain steady, gradually submerging the extensive underground infrastructure, which extends to a depth of over 1,400 metres.
Among the first areas to go underwater are the mine’s main service and operations levels. These include a canteen, maintenance halls and office facilities at the deepest level once used during active mining.
While no precise timeline has been set for full flooding, estimates suggest it will take years to fill entirely. The rate depends on seasonal water flows and geological conditions.
The shutdown plan includes dismantling removable equipment, cables, piping and machinery where safe and feasible. This work is being conducted under an approved closure framework monitored by authorities.
Maria Hänninen, environmental manager at Pyhäsalmi Mine Oy, said the mine has already remained operational longer than required to allow for potential reuse.
“We have given the pumped-storage project as much time as technically and legally possible,” she said in a written statement.
Some equipment left underground for possible future use must now be dismantled separately. The company will remove assets throughout the rest of the year in line with safety and environmental requirements.
While much of the mine will eventually be submerged, some activities will continue. Emergency response training is ongoing at 400 metres and is expected to remain unaffected. Education and testing programmes will also proceed, though some 5G testing equipment must be removed from lower levels in the coming months.
Nokela said the flooding process will affect long-term planning.
“We will need to reconsider how underground training and research can continue in future,” he said.
Once filled, the flooded chambers could be accessed again, but only with significant cost and effort. Until then, the countdown continues beneath the surface, as time and water pressure both increase.
HT
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Source: www.helsinkitimes.fi
