Geo-thermal Generation Gets Geysers Region Shaking

Calpine's geothermal electric generation projects in Northern California are facing criticism--for causing an increase in the number of earthquakes:

Calpine owns 19 of the 21 power plants operating at The Geysers, home to the world's largest underground steam fields in the fault-lined, rugged mountains bordering Anderson Springs.

In December, Santa Rosa and three other cities began pumping 11 million gallons of wastewater daily to The Geysers. There, it is injected one to two miles underground to replenish the steam fields. The superheated vapor spins turbines at the surface, where it is turned into electricity.

Calpine admits micro-quakes - those of less than magnitude 3.0 - are caused both by the extraction of steam from the earth and injection of water back into the ground to recharge the dwindling steam supply. Both processes cool the magma-heated rock miles beneath the surface, causing it to shrink, which triggers earthquakes as the rock adjusts, Oppenheimer said.

"We recognize we do cause quakes," Stark said.

Nearby homeowners are blaming damage to their foundations on the micro-quakes and are seeking damages; if successful, their lawsuits could be a thorn in the side of this renewable resource's use for electric generation.