PG&E is asking for as much as $64 million from ratepayers to fund earthquake studies around Diablo Canyon nuclear power plant, a sum nearly four times its original estimate.
The utility filed the request with the California Public Utilities Commission on Friday. The commission had previously approved a request for $16.73 million.
This increase is due primarily to the expanded scope of the seismic studies: the area PG&E will be studying for the 3D offshore studies and 2D onshore studies has more than doubled, states PG&Es application.
Nearly half of the estimated $64.25 million will be spent on high-energy, three-dimensional offshore studies to be conducted late next year from Point San Luis to Cambria. This work will use air guns to emit loud sounds into the ocean that penetrate into the Earths crust.
PG&E has applied for permits to do this work with the State Lands Commission. Approval will require significant environmental study.
The utility warns that the cost of the surveys could go even higher if it is not allowed to do the offshore work around the clock or if additional environmental requirements are imposed. Current plans call for the use of marine mammal observers, scout boats and fixed-wing aircraft to minimize the impact on marine life.
The seismic surveys will focus on where the Shoreline and San Simeon faults intersect with the Hosgri Fault. PG&E has been doing low-energy offshore seismic surveys since 2010.
Onshore two-dimensional seismic studies are scheduled for this fall. This work will use vibrating trucks and weight drops to send shock waves into the ground.
In its filing, PG&E said it is in its customers best interest to approve the funding request.
Enhanced knowledge of the seismic hazard near Diablo Canyon provides a clear benefit to PG&Es customers in that it enables PG&E to ensure safe operation of this valuable generation source, reads the rate request.
It could take several months for the CPUC to issue a ruling on PG&Es request.