St Gallen region reconsiders deep geothermal energy after failed project

Thirteen years after an earthquake stopped St Gallen's flagship geothermal project, the canton is preparing to look underground again. A new study commissioned by the cantonal government says parts of eastern Switzerland remain well suited to deep geothermal energy, reopening a debate that stalled after the 2013 failure.

The report names Buchs, Ebnat-Kappel and Widnau/Diepoldsau among possible locations for future drilling. It also identifies geological conditions that could support heat production, including glacial channels filled with loose rock and large fault and fracture zones that may allow water to circulate underground.

The findings matter because Switzerland still relies heavily on imported energy and is seeking domestic renewable sources. Geothermal systems could provide heat throughout the year, including during periods when solar output is low. The technology also fits the needs of towns and industry that require steady heat for buildings and processes.

The earlier project in the city of St Gallen ended after an earthquake linked to drilling operations. Its 4,400 metre borehole remains as a physical reminder of both the canton’s ambition and the consequences of incomplete knowledge beneath the surface. The new study offers a route back, with a more cautious development strategy.

A 178 page report gives the canton a geological case for trying again. The study concludes that the area examined is “geothermally attractive”, citing underground structures that could store and transmit hot water.

The most promising conditions occur where drilling can reach permeable fault or fracture zones. In the Rhine Valley, glacial channels formed during past ice ages extend roughly 300 to 600 metres below ground and were later filled with unconsolidated rock. These formations could offer a useful starting point for medium depth projects.

The report also points to larger geological structures at greater depths. Yet the subsurface remains poorly understood. Most existing boreholes in St Gallen serve geothermal probes and reach only 200 to 300 metres. They provide local information, but little direct evidence about the deeper formations needed for a large heat system.

That uncertainty shapes the report's recommendations. Rather than move immediately toward the deepest and most expensive targets, developers should test a shallower “play”, a defined area with geothermal potential. Data from those tests could guide later decisions on drilling, water flow and heat production. The approach would reduce the cost of early mistakes while improving the geological record.

The earlier St Gallen project ended with an earthquake and left deep geothermal development on hold across eastern Switzerland. The city had taken a pioneering role in seeking energy from far below the surface. Drilling reached 4,400 metres, but the project was halted after seismic activity struck during operations.

The consequences extended beyond the city. Ambitious projects elsewhere in eastern Switzerland failed to gain momentum, while regulatory work in Thurgau continued without producing a major installation. A proposed project by Geo-Energie Suisse in Etzwilen has remained on hold for years. The company is now advancing a project in Haute-Sorne, in the canton of Jura.

The St Gallen experience means any new proposal will face close scrutiny from residents, municipalities and regulators. Engineers will need to monitor pressure, water movement and seismic activity throughout the drilling process. Authorities will also have to define clear thresholds for pausing or ending operations.

The new report does not erase that history. It sets out a staged process that could generate more local evidence before a developer commits to deep drilling. For communities near Buchs, Ebnat-Kappel and Widnau/Diepoldsau, the debate will involve both the promise of local heat and the memory of what happened in the cantonal capital.

Four of the canton’s strongest sites could deliver more than 200 gigawatt-hours of heat each year. That estimate would cover about one-fifth of the renewable energy production target in St Gallen’s energy strategy, giving the project a scale that could matter for municipal heating networks and local industry.

The figure is a potential output, not a guaranteed result. A functioning system would require successful drilling, adequate underground water flow and infrastructure to move heat to consumers. The distance between a production site and a heating network could determine whether a project is economically viable.

The locations under discussion also have different local contexts. Buchs and the wider Rhine Valley contain urban, commercial and industrial areas that could use steady heat. Ebnat-Kappel presents a different setting in the Toggenburg region, while Widnau and Diepoldsau sit in a densely settled part of the Rhine Valley. Each site would require separate geological and planning assessments.

Deep geothermal energy would complement, rather than replace, other Swiss renewable sources. It could provide consistent heat when solar and wind production fluctuate. The report’s staged approach gives municipalities time to examine costs, potential customers and seismic safeguards before they support a full-scale project.

The next move will be a test, not an immediate return to the deepest drilling. The study recommends starting in a shallower geothermal “play”, where drilling can establish how rocks, fractures and underground water behave before costs rise further.

That sequence could help rebuild confidence after St Gallen’s earlier earthquake. It would also give the canton better evidence for decisions on permits, insurance, emergency procedures and public consultation. The report makes clear that greater depth brings both higher drilling costs and greater technical risk.

No major deep geothermal project has been developed in eastern Switzerland since the St Gallen failure. The stalled Etzwilen project in Thurgau shows how quickly uncertainty can freeze investment. Other cantons are watching developments in Haute-Sorne, where Geo-Energie Suisse is pursuing a new project.

For Swiss energy policy, St Gallen’s reassessment is a test of whether geothermal power can move from promising studies to carefully managed infrastructure. The canton must now decide how to translate geological potential into site investigations, local agreements and funding. Residents will judge the proposal through practical questions: what will be drilled, how seismic activity will be monitored, who carries the financial risk and where the heat will go. Those answers will determine whether the borehole becomes a model for a measured restart or another unfinished chapter.