Aging water main breaks, floods intersection in SF’s SoMa neighborhood

An underground water main dating back to the 1930s broke and flooded a major intersection in the South of Market neighborhood of San Francisco on Tuesday, buckling the pavement and snarling traffic.

Water began bubbling up through the roadway around 6:00 a.m. near the intersection of Second and Harrison streets and flowed toward Folsom Street, officials said. The leak caused a sinkhole measuring roughly 8 feet in diameter to form in the area.

A water main break at Second and Harrison streets in SF’s SoMa neighborhood early Tuesday, officials said. A water main break at Second and Harrison streets in SF’s SoMa neighborhood early Tuesday, officials said. Photo: Sophie Haigney / The Chronicle / Sophie Haigney / The Chronicle Photo: Sophie Haigney / The Chronicle / Sophie Haigney / The Chronicle Image 1 of / 5 Caption Close Aging water main breaks, floods intersection in SF’s SoMa neighborhood 1 / 5 Back to Gallery

A city work crew was on scene digging up the roadway to find the busted water main. Streets remained open as morning commuters slowly drove through water several inches deep.

Just before 9 a.m., workers were finally able to shut off the water flowing from the busted underground pipe. Businesses and residences along Harrison Street, between First and Third streets, remained without water service as of Tuesday afternoon, said Tyler Gamble, a spokesman for the San Francisco Public Utilities Commission.

“One, we are trying to return water service to customers in the area ASAP,” he said. “Second, we are trying to get to the pipe, repair it, and repave the road. Those are the things happening in tandem.”

He advised drivers to avoid the area, saying repairs would likely continue late into the evening.

The cause of the break was is under investigation, Gamble said.

“Age is likely a factor, though,” Gamble said. “The pipe we’re talking about is a 12-inch cast-iron pipe that was originally built in the 1930s.”

Gamble said that replacement of aging infrastructure like the busted water main is a major priority for the Public Utilities Commission. The department’s goal is to replace 15 miles of out-of-date infrastructure annually, and separately undertaking a major project to upgrade the city’s sewers.

“That’s the long-term plan, and then we work quickly to repair the breaks that do happen,” Gamble said.

Sophie Haigney is a San Francisco Chronicle staff writer. Email: shaigney@sfchronicle.com Twitter: @SophieHaigney