This is a historial post from Hiking the California Trail, a 1998/2002 book set by Bob Lorentz and Richard Nichols. Where possible an update has been provided.
Forty thousand people gathered in June 1979 to protest the construction of PG&E’s Diablo Canyon Nuclear power plant. Governor Jerry Brown addressed the huge crowd in a rousing speech at this largest event to question whether a nuclear plant should be allowed to operate on an earthquake fault. PG&E eventually won the war when the Diablo Canyon plant became fully operational in 1986 after years of protests and civil disobedience where 2700 people were arrested, but the victory came at great cost to the utility giant.
It seems that PG&E had a bizarre knack for placing nuke plants on earthquake faults. The first nuclear power plant that PG&E built, the Vallecitos plant near Livermore (now shut down), was just 200 yards from the Verona fault. The plant near Eureka on Humboldt Bay, located beside a series of faults, closed down in 1976, fortunately before a magnitude 7.0 quake struck in 1980 Another early PG&E nuke, proposed to be built at Bodega Head in Sonoma County in the early 1960s, turned out to be smack on top of the San Andreas fault. That plan was scuttled by a coalition that formed where no effective environmental movement had existed before. Only five years later PG&E proposed another nuclear power plant at Point Arena in Mendocino County. It was obvious they hadn’t learned their lesson: this time the site was a mile or two west of the big fault.
Perhaps when PG&E announced plans for the Diablo Canyon facility in autumn 1966, they felt they had learned their lesson about earthquake safety and nuclear power plants, boasting that the nearest fault was 45 miles away. Then in 1969 two oil company geologists discovered the Hosgri fault just 2.5 miles offshore from the Diablo plant already under construction. Later research shows that segments of the fault may run directly under the nuke plant. PG&E went into denial, disputing the existence of the Hosgri fault until 1973. Early resistance to construction at Diablo Canyon was slight. The Sierra Club endorsed construction, saying it was far preferable to the earlier plan of building a nuke plant in the Nipomo Dunes not far south. Organized opposition to the plant slowly developed. By 1978 thousands of people were demonstrating against the Diablo reactors. Several hundred were arrested. Then in spring 1979, a near meltdown occurred at Three Mile Island Nuclear Power Plant in Pennsylvania. As public awareness of the magnitude of the mishap spread, many people joined the movement to stop the Diablo Canyon plant. Despite the 40,000 protestors blocking the Diablo Canyon gates in June, completion and opening of the Diablo Canyon plant was finally allowed. Now the big question has become “When will the Diablo Canyon Nuclear Power Plant be shut down?”
—Originally Published in Hiking the California Coastal Trail: Guide to Walking the Golden State's Beaches and Bluff from Border to Border - Volume Two: Monterey to Mexico by Bob Lorentzen and Richard Nichols