LOS ANGELES (AP) - Citing harm to marine life, California coastal regulators on Wednesday soundly rejected a utility's plan to map offshore earthquake faults near a nuclear power plant by blasting loud air cannons.
The unanimous vote by the California Coastal Commission came after an hours-long public hearing attended by environmentalists, fishermen and residents who were overwhelmingly opposed to the seismic testing.
The proposed survey by Pacific Gas & Electric Co. involves firing sonic pulses into the ocean. Sensors on the seafloor would pick up the echoes to create 3-D maps of geologic faults that the utility said are needed to understand the seismic hazards around the Diablo Canyon facility.
"If you live near a nuclear plant, wouldn't you want more certainty in the assumptions that are being made?" asked Mark Krausse, a PG&E director.
But commissioners said the impact to sensitive marine mammals along the Central Coast would be too great, and they felt PG&E did not make the case that such testing was necessary.
In a statement, PG&E said it was disappointed with the decision and will evaluate its next move. It could reapply for a permit, but several commissioners indicated they would be hard-pressed to change their minds if the issue came up again.
The commission's staff had urged the panel to reject the plan. In a report this month, the staff said sonic blasts would cause "significant and unavoidable impacts to marine resources." More than 7,000 sea mammals would be disturbed by the ear-piercing noise, including fin whales, blue whales, humpback whales, and harbor porpoises.
PG&E acknowledged that the noise could cause short-term disruption to animals, but said similar research has been done around the world without long-term harm.
The damage that strong shaking can cause to nuclear reactors came under scrutiny after the 9.0-magnitude earthquake off Japan's coast triggered tsunami waves, which swamped the Fukushima Dai-ichi plant last year.
Even before the Fukushima disaster, state law mandated that utilities conduct extensive seismic studies of nuclear facilities, but did not specify the type of research.
Perched on an 85-foot bluff above the Pacific, Diablo Canyon sits within three miles of two underwater earthquake faults, including one that was discovered in 2008.
PG&E came up with a four-pronged approach that includes the use of high-energy seismic imaging technology. Under the ratepayer-funded study, a research boat would tow 18 air guns that would emit sonic blasts into the ocean every 10 to 20 seconds for several days. The utility had hoped to conduct the study between November and December to avoid peak breeding and migration seasons.
In August, a State Lands Commission environmental impact study determined there would be unavoidable consequences to marine life during the testing. But the panel ultimately decided the project's benefits outweighed the environmental risks.
Scores of conservation groups and other parties sent letters to the coastal commission opposing the project and turned out in force at Wednesday's meeting in Santa Monica. Some wore "Stop Ocean Blasting" T-shirts, and others held signs.
Michael Jasny with the Natural Resources Defense Council testified that the air guns would inflict "severe and profound insult" on sea life.
Representatives from the Northern Chumash Tribal Council said their ancestors have inhabited the coastline for thousands of years. They urged the panel to protect the ecosystem.
"We cannot let this happen," tribal administrator Fred Collins said. "Please do not let this project go forward."
Mandy Davis, spokeswoman for a newly formed group called the Citizens Opposing Acoustic Seismic Testing, said the Pacific would become an "acoustic prison" if the project went forward.
Many claimed the utility had done too little to explore other, less damaging options and said it should analyze data it collected from previous studies before embarking on a new one. Krausse of PG&E countered that different studies provide different information.
To minimize impact to sea life, PG&E proposed starting off with one air cannon at a low decibel before ramping up to full power. It also planned to have spotters on the vessel and in an aircraft to alert operators of marine mammals in the region. Air guns would be silenced and work would cease if an animal strays too close.
The twin-reactor Diablo Canyon generates enough electricity to power more than 3 million homes in Central and Northern California. After the Japanese nuclear crisis, the utility asked federal nuclear regulators to delay issuing extended operating permits until thorough seismic studies are completed. The permits expire in 2024 and 2025.
The Nuclear Regulatory Commission does not require 3-D fault mapping for license renewal.