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The United States Energy Department, concerned about earthquake risk, will impose new safeguards on geothermal energy projects that drill deep into the Earth's crust.
The new policy is being instituted after a project in California that used the new technology was shut down by technical problems and encountered community opposition, federal documents indicate.
The project, by Seattle-based AltaRock Energy, would have fractured bedrock and extracted heat by digging more than two miles beneath the surface at a spot called the Geysers, about 100 miles north of San Francisco. The company ran into serious problems with its drilling and faced accusations from scientists and local residents that it had not been forthcoming enough about the earthquake risk. AltaRock denied those accusations.
The documents, provided to The New York Times by the Energy Department, indicate that the Geysers project has run through $6 million in federal financing in several unsuccessful efforts to drill to the necessary depth. As a result, the Energy Department "considers the project in the Geysers to be concluded," according to a letter addressed to Henry A. Waxman, the California Democrat and chairman of the House committee on Energy and Commerce.
The letter, dated Dec. 30, is signed by Cathy Zoi, an assistant energy secretary. The Times reported in early December that AltaRock had removed its drill rig from the site and informed the department that the project would be abandoned, but the company had refused to comment publicly.
In a second document dated Sept. 11, 2009, but not previously disclosed, the department concluded that earthquakes that would have been set off by the AltaRock project would "not have a significant impact on the human environment." And in another endorsement of the company, the department later awarded AltaRock $25 million to try a similar project at the Newberry Volcanic Monument near Bend, Ore.
The Oregon project was one of 123 geothermal projects in 38 states that received $338 million through the Obama administration's economic stimulus package, Ms. Zoi said in the letter.
Two seismic experts who read the documents said the message about the perils and potential of geothermal energy was unclear. But Ernie Majer, a seismologist and deputy director of the Earth Science Division at Lawrence Berkeley National Laboratory in California, said that the new standards were a welcome development. The letters show that the department "is being ultra-careful about any induced seismicity," he said, referring to earthquakes triggered by humans.
Among the new safeguards are requirements that projects monitor ground-motion sensors and other data and have an approved plan to shut down if earthquakes induced by the drilling are too powerful. Companies must also file estimates of expected earthquake activity and submit project proposals to outside experts for a review of the risks and the likelihood of success.
Ms. Zoi conceded in her letter that the department's findings were "likely to have little practical effect on the AltaRock project at the Geysers," because the project apparently no longer exists. But she said that the defunct project and the findings "have provided valuable lessons."
In a statement responding to questions on the documents, Stephanie Mueller, a spokeswoman for the department, said that those lessons "will help the United States succeed in safely harnessing geothermal energy."
Donald O'Shei, AltaRock's chief executive, said in an e-mail message that the company was pleased by the department's finding that the Geysers project would not have had a significant impact on people in the area.
Regarding the Oregon project, Mr. O'Shei said that the company was "working on an initial planning process for the technical, permitting, and community education and outreach aspects of the project."
Mr. O'Shei added, "Bend is located approximately 22 miles away from the demonstration site, which is in a sparsely populated area to the west of Newberry in central Oregon."