PG&E plans to use underwater ‘air cannons’ emitting 250-decibel blasts every 15 seconds for 12 straight days to map earthquake fault zones near Diablo Canyon nuclear plant.
photo: The Diablo Canyon nuclear power plant near San Luis Obispo, Calif. PG&E was ordered by the California Public Utilities Commission to conduct the risk assessment. (Phil Klein, Associated Press / April 26, 2001)
Over objections of Central Coast residents and environmental groups, Pacific Gas & Electric plans to map earthquake fault zones near its Diablo Canyon nuclear plant by blasting high-decibel air cannons under the surface of the ocean.
PG&E’s plan calls for towing a quarter-mile-wide array of underwater “air cannons” that emit 250-decibel blasts into the ocean every 15 seconds for 12 straight days. The sonic reflections would be picked up by underwater receivers and analyzed to provide detailed 3-D images of the geometry, relationships and ground motions of several fault zones near the Diablo facility, which generates enough energy to meet the needs of more than 3 million Northern and Central Californians.
"What we’re after with this survey is the geophysical equivalent of a CT scan — a combination of imagery and information that we could slice and dice and scrutinize in great detail," said Jearl Strickland, director of nuclear projects for PG&E. "These kinds of surveys are being performed right now around the world with no problems."
Opponents say the method threatens sea creatures from Central Coast rockfish to whales, and they dispute PG&E’s claims that there are no alternative, less harmful technologies available for the job.