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The Seismic Saga of the Humboldt Bay Nuclear Power Plant

In November 2021, PG&E petitioned the Nuclear Regulatory Commission (NRC) to terminate the license for the Humboldt Bay Plant #3, the first commercial nuclear power plant in California. The petition was the official end to a story beginning in the 1950s before global seismic networks, plate tectonics and paleoseismology. The Humboldt Bay site just south of Eureka, California was chosen because of available PG&E property with proximity to water, no known faults and a much less resistant local community compared to proposed sites in Bolinas and Point Arena. The 63 MWe reactor became operational in August 1963 and, for the next 14 years, provided most of the electric power to the Humboldt Bay region. The first local seismic net was established in 1974 when the Atomic Energy Commission (NRC predecessor) became concerned about nuclear plant seismic safety in the wake of the San Fernando earthquake. Teknekron (predecessor of TERA) Corporation established a network of 16 stations, providing the first detailed picture of regional earthquake activity. A scheduled maintenance shutdown in 1976 became permanent when a fault discovered in a nearby quarry led to an investigation of active faulting. Local activists were recognized as official intervenors by the NRC that likely prolonged the shutdown. Woodward-Clyde (now part of URS) began field studies that were still underway when PG&E submitted an application to permanently close the plant and begin the decommissioning process. The March 1979 Three-Mile Island accident had changed the nuclear landscape, and it was not economical to meet the new standards. The story is not completely over; waste still resides on site, now stored in casks just above the modeled tsunami inundation zone. An unintended consequence of Plant #3 is the wealth of geologic data the seismic and tsunami safety studies provided. The former plant site sits only 13 km above the Cascadia interface, a kilometer from the Little Salmon fault, and adjacent to two smaller faults.

Session: Characteristics, Hazards and Evolution of the Gorda Region of the Cascadia Subduction Zone [Poster]

Type: Poster

Room: Evergreen Ballroom

Date: 4/21/2022

Presentation Time: 08:00 AM Pacific

Presenting Author: Lori Dengler

Student Presenter: No

Additional Authors