Geothermal Power Plant Triggers Earthquake in Switzerland
Even environmentally friendly alternative technologies can have negative impacts which are difficult to predict. The citizens of Basel learned this first-hand as they were shaken by an earthquake of magnitude 3.4 on the Richter scale, followed by 60 lesser aftershocks, including a quake of magnitude 2.5 a week after the initial quake, and another tremor of 3.1 as recently as 6 January, attributed to changes as underground pressures at the now discontinued project site return to normal. The engineers and officials of Geopower did inform the authorities and the public that the proposed Deep Heat Mining project posed a risk of triggering small tremors. Quakes of the magnitude actually experienced, however, were not anticipated. The public is also questioning whether the communication of this risk, by a brief statement buried in a press release, was sufficient to prepare residents.
The Geopower Deep Heat Mining project is the first commercial application of the so-called hot fractured rock technique, which allows recovery of heat from dry rock. The Geopower engineers intended to use the 200C temperatures at 5000 meters to heat injected water which is then pumped back to the surface for recovery. The technique relies on the fracturation of existing pores and crevices by injection of cold water. The fracturation creates a path for water to cycle through the hard granite, so that the heated water can be brought back to the surface through a separate borehole a distance away from the injection hole. Most geothermal power projects tap into reservoirs of heated water rather than dry rock. However, recent reports suggest that earthquakes caused by mankind are not uncommon.Christian D. Klose of Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York, reports that over 200 quakes can be attributed to mankind's activity in National Geographic. The most severe example was a quake of magnitude 5.6 in Newcastle, New South Wales, Australia, an area not prone to seismic activity. The quake hit on December 28, 1989, killing 13 people, injuring 160, and causing US$3.5 billion in damages--more than the entire value of the coal mined over the life of the Newcastle operation. Klose suggests that similar activity could be caused by CO2 sequestration, the process of pumping CO2 into deep underground reservoirs.
Unlike Newcastle, Basel experiences dozens of tremors every year, 3 or 4 of which may hit the 3.4 magnitude similar to the Geopower triggered quake. Experts suggest that the recent quake was percieved as much worse because it was triggered from only 5000 meters below the surface. Residents fears are also compounded by the fact that Basel sits directly over a fault to which the worst earthquake ever to hit Europe is attributed. The quake, estimated to have been about a 6.5 on the Richter scale, occurred in 1356, toppling medieval castles and church towers. Experts indicate that a similar quake today would bring down about 4% of existing buildings, cause SFf80 billion ($66.3 billion) in damages, and threaten public safety due to the chemical and nuclear industries active in the area.
Neighboring Germans could feel the quake and political reverberations have reached Berlin, where questions are being raised about 70 to 80 geothermal projects which are seen as essential to Germany's planned exit from nuclear power generation. A speaker for the German Environmental Agency indicated that the events in Basel are being watched closely, but that they see no grounds for panic, and investment in geothermal power in Germany is anticipated to continue unabated. The President of the German organization for geothermal energy, Horst Rüter, was quoted in the German daily Handelsblatt saying, "In principal, the residents of Basel should be happy" because tensions have been released which could have triggered a more significant quake if left to build up. Swiss earthquake researchers have vehemently denied the validity of Rüter's opinion.
The firm Geopower was founded specifically to pursue the geothermal power opportunity, hoping to warm 2700 homes and power 10,000. It includes two Swiss Cantons as well as 8 regional energy providers amongst the stockholders. The question of whether Geopower will be allowed to return to drilling remains under evalution, with US$50 million already invested at risk.
Via ::Handelsblatt (german only)