A resident had called 911 at about 11:20 a.m. Wednesday, June 18, and told dispatchers of a hissing sound coming from a rupture in the asphalt. When firefighters arrived, they confirmed the hissing, noted that the asphalt had a visible "bulge," and cordoned off the area, said Battalion Chief Rob Lindner of the Woodside Fire Protection District.
Around noon, working with the San Mateo County Sheriff's Office, firefighters went door-to-door to inform residents who were at home on Valley Oak, Acorn and Bayberry streets to shelter in place. Firefighters would have evacuated residents in the immediate vicinity of the leak, but none were home, Mr. Lindner said.
The shelter-in-place order was lifted around 3:20 p.m.
PG&E crews had the 3-inch low-pressure gas main repaired by 9 p.m. that night after a day of digging, repairing and checking for methane leaks elsewhere in and around the neighborhood, said company spokesman Jason King. The areas checked included Corte Madera School, Los Trancos Road, and across Alpine Road around Canyon Drive, according to a PG&E map.
Crews found no leaks and there were no reported injuries, Town Manager Nick Pegueros said.
Firefighters remained on the scene for about four hours, Mr. Lindner said.
An investigation is underway. The leak is thought to have come from the "weld" of a plastic joint located several feet away from the asphalt rupture, Mr. Pegueros said. PG&E crews repaired the joint after having dug up the street and installing a temporary bypass to allow homes to receive gas while the line was being repaired, he added.
The area around the joint showed no indications of seismic movement or damage by construction equipment, Mr. Pegueros said.
The joint is probably 30 to 40 years old, as old as the subdivision, he said. If it is determined to have caused the leak, a key question will be whether there are other joints of the same vintage elsewhere in the system.
"What we know is (that) we're completely up to date on our inspections," Mr. King said.
People should not be drawing comparisons between this incident and those involving "large mains at high pressure," Mr. King added.
Gases need to be in a contained space to be vulnerable to explosion. This leak had been venting gas to the air, but wind was sending it toward residences, Mr. Lindner noted. And it was a main, not a 1-inch residential line.
"That's a significant amount of gas," Mr. Lindner said in explaining the shelter-in-place order. "It could pose a threat to an immediate area."
"It's difficult to assess" the danger, said Mayor Ann Wengert. But the rupture in the road "from a lay perspective, would cause concern and from my perspective, (should cause PG&E) to jump it up to the top of the list."
Mr. Pegueros did not hesitate. "There was clearly enough pressure to bubble the road," he said. "I would say that yes, there was a danger to the community. We were very fortunate that the incident was discovered. ... There were multiple possibilities — a tossed cigarette, a weed whacker, a vehicle passing over — that could have sparked or ignited the gas. We're lucky that didn't happen."
What about such scenarios? "I can't really speculate on what possibly could have happened," Mr. King said, noting that he is a company spokesman and not a gas-line expert. Could he make an expert available? "It's not our company policy. We need to be working to keep our system safe. Again, the investigation is ongoing."
And the pavement rupture? "Part of (the investigation) is looking at what caused the pavement deformation," Mr. King said.
PG&E will be contacting some 200 customers in the vicinity, Mr. Pegueros said. A robo-call? "It better not be," he added. "There should be an opportunity for a dialogue."
In a letter to Mayor Ann Wengert, PG&E local government relations representative Scott Hart said PG&E's "customer care team" called 220 households. Of those, there were 66 live conversations and 107 voice mails, he said. Forty-seven calls did not connect and the company received one return call.
Residents with concerns can call Austin Sharp at PG&E at (650) 730-4168, Mr. King said.