Earthquake monitors proposed for seafloor near California's Diablo Canyon power plant

San Luis ObispoApril 11, 2012 

The California Coastal Commission today is expected to approve plans by PG&E to place six earthquake activity-monitoring devices on the seafloor off Diablo Canyon nuclear power plant.

Four of the monitors would be on the seafloor for 10 years or more and would be connected to shore with an 11-mile-long cable. Two of the monitors would be in place for four weeks.

The commission is holding its monthly meeting in Ventura today through Friday.

The devices, known as ocean-bottom seismometers, are part of PG&E efforts to learn more about the Hosgri and Shoreline earthquake faults and the potential danger they pose to the nuclear power station. They would be arrayed from the nuclear plant north to Point Buchon.

“The accurate, real-time data to be gathered would be shared with public universities and agencies through the U.S. Geological Survey and would help the scientific community better understand the characteristics of earthquakes in the vicinity of Diablo Canyon nuclear generating station,” the Coastal Commission staff report states.

The monitors would be placed on both sides of the Hosgri Fault, the area’s major seismic feature. They would record any earthquake activity along the fault, said Jearl Strickland, director of nuclear projects at Diablo Canyon.

Although the permit would be limited to 10 years, PG&E could apply to extend the project if the monitors are generating useful data, Strickland said. The project also needs the approval of the State Lands Commission, the U.S. Army Corps of Engineers and the state Department of Fish and Game.

Coastal Commission staff has identified two potential environmental impacts of the project: damage to the ocean floor and commercial fishing. The long-term presence of the cable could damage bottom-dwelling organisms.

Commercial fishing gear could also become entangled on the monitoring units. To compensate for that, PG&E has offered to contribute $33,600 to the California Lost Fishing Gear Recovery Project.

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