Geothermal drilling may cause quakes

June 24, 2009 7:13:59 PM PDT
A geothermal energy company is raising concern among people who live near the Geysers in the North Bay. That's where drilling is underway in eastern Sonoma County to harness energy from the heat found within the earth. But that drilling may contribute to earthquakes.

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In the frenzy for underground steam, the Geysers, which straddles the Lake and Sonoma County border is the largest geothermal power project in the world.

Holes are drilled deep into the ground and water is injected to extract steam. But all of this sometimes triggers small earthquakes.

"It rattles the dishes. it rattles the cabinet doors. We've always had quakes up here but they were always quite small," said Anderson Springs resident Richard Matchie.

But now folks who live in the area are bracing for more.

A Sausalito start-up company, AltaRock Energy, has begun drilling deeper into the ground, more than two miles deep to capture its heat.

"Our goal is to develop a new technology to develop geothermal energy that makes it more widespread and available than it is today," said AltaRock Energy VP Jim Turner.

The firm secured financing of $36 million from the energy department and Google is also one of the investors.

But AltaRock Energy uses almost the same method of deep ground drilling as a European company that reportedly caused a 3.4 magnitude earthquake three years ago in the medieval town of Basel, Switzerland.

The New York Times reports that Altarock Energy left crucial details of the Basel quake out of its seismic impact report.

Turner disputes that.

"We did mention Basel to the regulators and to the people in the Geysers area," said Turner.

He says the drilling will be safe and seismologist David Oppenheimer believes the deep drilling will cause only small tremors, not big ones.

"They will be creating fractures probably no bigger than magnitude 2.5. That clearly is not any significant hazard to anybody," said Oppenheimer.

But some residents like Larry Sexton are still worried.

"Oh yeah. It doesn't sound good, going that deep and we've got enough around here," said Sexton.

One thing is for sure -- big or small quakes have become a fact of life near the Geysers.

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