Fifteen minutes after the ground stopped shaking Sunday morning, a computer model at Pacific Gas and Electric Co. spat out a prediction: Roughly 85,000 customers would be without power as a result of the quake, with many of them clustered around Napa. The utility started deploying its crews, trucks fanning out across the Wine Country before dawn.
"That gave us the first indication of how big an event this is and an idea of what resources we'd need and where we'd need them - so we had that right out of the gate," said Barry Anderson, PG&E's vice president of emergency response.
In the end, roughly 70,000 businesses and homes lost power following Sunday's early-morning earthquake near American Canyon. PG&E was able to restore electricity to almost all of them within 24 hours, finishing the rest by noon Monday.
"That's remarkable - that's a good time" said Bob Bea, a UC Berkeley professor emeritus in civil engineering. "For once, PG&E is due an accolade."
It wasn't just computer modeling that helped PG&E restore service so quickly after the Bay Area's biggest earthquake in 25 years. Wireless SmartMeters, which PG&E has installed on every building it serves, automatically signaled the utility when their buildings lost power.
"Back in '89, with Loma Prieta, we had outage calls from customers, and that was it," said Anderson, who is leading PG&E's response to the Napa earthquake.
PG&E's sprawling networks for delivering electricity and natural gas appear to have suffered little lasting damage from the 6.0-magnitude quake. Although 12,000 feet of electric lines were knocked down by the shaking, none of the company's substations dropped offline. More than 400 phone calls poured in from customers who smelled natural gas, but only 20 buildings lost gas service, in each case as a result of structural damage.
In the past, PG&E has at times needed days to restore electricity to areas hit by winter storms. Following Loma Prieta, which knocked out power to more than 1 million customers, the utility was able to bring power back to 900,000 within 24 hours, but still had 55,000 customers without gas a week later.
So what made the difference with this quake?
Part of the answer is technology. The computer system that predicted quake damage and the SmartMeters that reported it weren't in place 10 years ago, much less 25. Part of it is investment. The deadly 2010 explosion of a pipeline beneath San Bruno forced PG&E to inspect its natural gas system and replace miles of transmission pipes and smaller distribution lines.
Part is preparation, with PG&E holding its latest earthquake simulation for employees in May. And part is luck. Not only was the Napa quake smaller than the 6.9-magnitude Loma Prieta temblor, but the places it hit did not undergo liquefaction, in which shaking soil starts to move as a liquid. Liquefaction beneath San Francisco's Marina district during Loma Prieta snapped natural gas lines and triggered fires that consumed apartment buildings.
Natural gas is suspected in one fire that followed Sunday's quake, a blaze that destroyed four mobile homes. PG&E says its gas line into the mobile home park did not break. However, mobile home parks typically run multiple gas lines off of one meter, maintaining the lines within the park on their own. A rupture could have occurred there, according to the utility.
Bea hopes the utility continues to hunt for leaks in its North Bay natural gas system, even if it hasn't found any significant ones so far. "We've got service re-established - is that service as safe as it should be?" he said. "I would hope PG&E remains vigilant that there could be undetected leaks."
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