Geothermal project destroying town?

[ben_meyers]

Buildings Crack Up as Black Forest Town Subsides
By Mark Waffel in Berlin

In the last six months mysterious cracks have appeared in buildings in a picturesque Black Forest town. As the cracks have grown, so have residents' concerns. The problem is the town is slowly sinking into the ground. A geothermal project is apparently to blame.(snip)
But what happened next took the forward-thinking town council by surprise. By trying to do its bit for the environment, the council appears to have upset a delicate balance. A couple of weeks after carrying out the work, the first cracks in the facade of buildings started to appear. So far, Staufen Mayor Michael Benitz told SPIEGEL ONLINE, the damage has been primarily cosmetic. "No buildings are in danger of collapsing," he said.
As the earth beneath the town has given way, large cracks have appeared in the town hall, a church, two schools and over 50 homes. The first of the mysterious cracks, which have got bigger and bigger, was spotted two weeks after the town council embarked on an innovative geothermal project.

http://www.spiegel.de/international/zeitgeist/0,1518,541296,00.html

OOPS!

[Sinistrous]

1. This is the first time I have heard of subsidence being a consequence of

tapping geothermal energy. Subsidence was not mentioned in the (admittedly very few) articles I have read on the subject.

It would be interesting if others having a more substantial knowledge of the subject would weigh in with comments.

Sinistrous

[Viva_La_Revolution]

2. First I've heard of too, but it does make sense...

in this case, removing something from the earth (heated air or water) and changing the pressures on each layer. I've always had similar worries about carbon sequestration.

[kristopher]

3. confined groundwater?

Doesn't seem to be a pervasive issue for geothermal.

"According to Breder, when the geothermal probes were sunk into the ground, the contractors came across confined groundwater. It is possible, he said, that the digging might have reduced the water's pressure and caused some of it to trickle away. As a result, the earth's surface could have sunk.

Breder added that although it was fairly common for geothermal projects to cause very minor damage to buildings -- especially ones with structural problems -- the damage to buildings in Staufen was unusual. "I have never encountered anything like this -- not to this extent," he said. "Also colleagues who I've spoken to about this have not seen anything like this."

The town's 8,000 residents are now waiting to see what will happen next. Repairs to buildings cannot start before the cause has been conclusively established and the town stops sinking. Mayor Benitz said it was still too early to say how severe the damage will be in the end.

"Will the earth continue to sink or is it going to stop?" he wondered. "If it does stop now, then we will have got away lightly, but if it does continue it could turn out to be quite bad.""