Fishermen and conservationists — groups that are often at odds with one another — joined Thursday to express grave concerns about plans by PG&E to use very loud sounds to explore earthquake faults around Diablo Canyon nuclear power plant.
The utility plans to use air guns towed behind a research vessel that would emit sounds as loud as 250 decibels into the ocean, said Stuart Nishenko, PG&E’s senior seismologist.
In comparison, a jackhammer produces a 100-decibel sound, and a stun grenade makes a noise as loud as 180 decibels.
The effects of these loud sounds on ocean life are the main environmental concern of the work, said Cy Oggins, chief of environmental planning with the State Lands Commission, which will decide whether the research can take place.
Sounds at that level could affect sea life ranging from whales to fish larvae.
“This is nuts, what you are planning on doing,” said Tom Hafer, a Morro Bay commercial fisherman.
Hafer and other commercial and recreational fishers told state officials Thursday they are concerned the research would scare fish away from the area. They also think the research is unnecessary.
“We know there are earthquake faults in the area,” Hafer said. “This isn’t going to prevent a quake from happening.”
The fault research is being done as a prerequisite for extending Diablo Canyon’s operating licenses to 2044 and 2045. Many local elected officials demanded that the work be done in light of the March 11 earthquake and tsunami in Japan that caused meltdowns at a nuclear plant there.
The work is intended to more accurately define the length and depth of the Hosgri, Shoreline and San Simeon faults, Nishenko said. There is concern that, if these faults connect, they could produce a more powerful quake than seismologists currently think can happen.
The research vessel would tow a large array of air guns and microphones behind it as it travels in elliptical patterns from Cambria to Point San Luis. In all, the vessel would travel more than 1,300 miles.
The sound generated by the air guns would penetrate into the Earth’s crust up to depths of 10 kilometers and bounce back. Listening to echoes of this sound will allow scientists to generate a three-dimensional picture of the faults, Nishenko said.
The work would start in September 2012. If the work proceeds uninterrupted, it would finish in December of that year. However, it could last as long as six months if stoppages due to weather or conflicts with marine mammals are required.
The State Lands Commission is expected to hold a public hearing on the project in December.
The commission is one of a number of state agencies that must approve the work before it takes place.