Officials mull seismic tests near PG&E's Diablo Canyon nuclear plant

AP File PhotoPG&E wants to discover if faults found in 2008 near Diablo Canyon nuclear power plant are connected to others that have already been studied

Plans to use an array of powerful air cannons in an undersea seismic study near a Central California nuclear power plant have federal and state officials juggling concerns over marine life with public safety.

PG&E wants to use big air guns to emit strong sound waves into a large, near-shore area that includes parts of marine reserves to make three-dimensional maps of fault zones, some of which were discovered in 2008, near its Diablo Canyon nuclear power plant.

But a state study — mandated by Assembly Bill 1632, which was signed into law in 2006 — found the project is likely to have “unavoidable adverse effects” on marine life and the environment. Biologists, environmental groups and fishermen have opposed using the high-energy air guns, saying the blasts have the potential to harm endangered whales, California sea otters and other creatures frequenting these waters.

“There are many uncertainties on the impact of this type of operation on whales, especially since we have not seen this type of large air gun survey off California for a long time,” said John Calambokidis, an Olympia, Wash.-based marine biologist who has studied Pacific Ocean whales for decades.

The $64 million, ratepayer-funded effort to understand seismic threats to the plant has intensified since the disastrous 2011 Tohoku quake and tsunami, which disabled reactors at Japan’s Fukushima Dai-ichi nuclear power plant. Quake experts were surprised by the 9.0-magnitude quake on a fault that scientists did not believe would produce a quake stronger than 8.0.

Although the Japan disaster demonstrated that predicting the strength of a quake on a given fault is an inexact science, PG&E wants to know if the newly discovered faults near San Luis Obispo are connected to existing ones that have already been studied.

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