Staufen 2007: seven holes for a heating system, and the old town has been rising ever since, by 65 centimetres

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Staufen im Breisgau lies on the edge of the Black Forest, about fifteen kilometres south of Freiburg. A castle ruin above the vineyards, an old town with narrow lanes and a town hall with a stepped gable. Legend has it that the devil came for Doctor Faustus here around 1541. Since 2007 the town has been telling a different story, and this one is documented.

Seven holes for a heating system

In 2006 and 2007 the town hall was renovated, and the town wanted to heat and cool it with geothermal energy. In September 2007 a company drilled seven holes into the ground behind the town hall, approved down to 140 metres. Each hole received a borehole heat exchanger, a pipe in which a fluid circulates and brings heat up from the depth. Afterwards each borehole is grouted around the pipe. This narrow gap is called the annulus, and it has to be sealed.

Two weeks after the drilling, in October 2007, the first cracks appeared on the town hall and the houses next to it. Then the surveyors measured something that should not happen in an old town: the ground was rising, at first by up to eleven millimetres a month. Because it does not rise evenly everywhere, the houses crack. By spring 2013 more than 260 property owners had reported damage to the town. A crack runs through the historic town hall too. A laundry on the Schlossberg was lifted by 45 centimetres and had to be demolished, and so did the town's technical services building.

Wolfgang Trch used to run an inn in Staufen. In 2017 he told the Stuttgarter Zeitung that in his house, with oak beams around four hundred years old, even the concrete floor slab had been split and the house torn in two. He no longer dared to open the windows in case the panes burst. His words: it is like living on top of a volcano.

What lies beneath the old town

According to the State Office for Geology, Raw Materials and Mining of Baden-Württemberg, the top layers beneath the town hall are loam, sand and gravel. From 28.6 metres down begins the gypsum keuper, a gypsum-bearing rock of the Grabfeld Formation. Between 61.5 and 126.1 metres it contains anhydrite, which is gypsum without water. Further down, in the Erfurt Formation and the Upper Muschelkalk, groundwater is under pressure. It is called artesian: drill into it and it rises by itself.

The boreholes went through the gypsum keuper into those layers. In at least one probe the annulus was not tight, as the state office describes it today. The pressurised water found its way up, straight into the layer containing anhydrite. Anhydrite that receives water turns into gypsum. Pure anhydrite needs up to 61 percent more space in the process, because the water is built into the mineral, and clay minerals swell as well. Specialists call this gypsum keuper swelling. Picture a cellar full of dried peas, and someone turns on the tap.

Fighting back

By the end of 2009 all seven boreholes had been sealed with cement at the bottom. But the water was already in the layer, and the pressure from below remained. Since April 2012 the so-called drawdown operation has been running: three wells pump out the pressurised water, day and night. In summer 2026 they extracted around 5.4 litres per second together. At the beginning of 2026 a stronger pump was installed, and the water level dropped by about another 18 metres. A larger pump would not fit into the well.

It works. From eleven millimetres a month at the beginning, the rate fell to at most 0.84 millimetres a month in the period from April 2025 to March 2026, measured at two points. The area that is still rising gets a little smaller every year. By then the old town had risen by around 65 centimetres at its highest point and shifted sideways by up to 52 centimetres. Nobody can say exactly how long the water in the rock will keep acting, the town writes. No end to the pumping has been announced.

Not the only case

In Rudersberg in the Rems-Murr district, a total of twenty borehole heat exchangers were drilled between 2007 and 2009. In one failed borehole the annulus remained open for more than five and a half years. There, too, the gypsum keuper swelled, and a residential area rose by up to 6.9 millimetres a month in August 2012. Since then the uplift has almost come to a standstill. The state office documents such damage cases publicly. One point matters to us: geothermal energy is not the problem. The problem is a leaking hole in rock that does not tolerate water.

Is it under my town?

We searched the 1:250,000 geological overview map of the Federal Institute for Geosciences and Natural Resources for every unit containing gypsum or anhydrite. There are 6,075 areas, 7,611 square kilometres in total, about three times the size of Saarland. They run like a belt through the middle of Germany, from Württemberg and Franconia via Thuringia and northern Hesse to southern Lower Saxony and Saxony-Anhalt. They are densest between northern Hesse and Thuringia.

And here is the honest part: this map shows what lies at the surface. Beneath the town hall of Staufen it shows only loam, sand and gravel, because the gypsum keuper begins there only at a depth of 28 metres. A surface map does not replace a site survey. It only tells you where to look more closely. In the orecast map, the Geology and Minerals section shows the rock at every point, with its source, even without signing in.

A sign of confidence

The cracks in Staufen now grow only a little, and the first major repairs are being planned or are under way. Right in the centre of the uplift, a new archive and the rebuilt technical services building are to be constructed, with work scheduled to begin in autumn 2026. The town calls it a sign of confidence. Some scenes in the video were created with AI and are labelled as AI reconstructions or AI illustrations. The photos of the cracks, the figures and the cross-section through the layers are based on the sources named.

Illustrations generated with AI.