Crews responded to the intersection of Larkin and McAllister streets overnight after rainwater began to pool in an underground vault directly over a steam pipe, which evaporated the water and caused steam to come up into the intersection, SFPUC spokesman Tyrone Jue said.
A few months ago, an emergency water pipe for the San Francisco Fire Department broke, damaging a storm drain at the intersection, Jue said.
Since then, steam has often been seen coming up in the intersection because "anytime any water pools up or passes by that steam pipe, it heats up and evaporates," he said.
Crews are working this morning to suck the water out of the vault, and will look to see if there was any damage to the pipe, Jue said.
One southbound lane of Larkin Street will be closed between McAllister and Fulton streets until at least the end of today, Jue said.
The SFPUC is also working on a long-term fix to prevent similar problems from occurring at the intersection in the future, and the street may be closed longer depending on the extent of damage found inside the vault, he said.