The sinkhole was reported at about 5 p.m. Monday at the intersection of Lake Street and Second Avenue, and eventually grew to be about 20 feet in diameter and 10 feet deep, SFPUC spokesman Tyrone Jue said.
Investigators believe the sinkhole formed when a 19-inch brick sewer line below the roadway ruptured, causing the asphalt and concrete to give way, Jue said. He said crews estimate the line is at least 100 years old.
Jue had initially said Tuesday that crews expected to complete repairs at the site by this Friday, but SFPUC officials said later in the day that repairs will take two weeks because an entire block of the sewer line on Lake Street has to be replaced.
The intersection remains open to traffic, but minor traffic delays are expected. Portions of the street may be temporarily closed as the repair work progresses, SFPUC officials said.
Jue said Tuesday that the sinkhole highlights San Francisco's aging sewer infrastructure and warned that similar incidents could occur in the future as decades-old pipes deteriorate.
The SFPUC is continuing its Sewer System Improvement Project, a multi-billion-dollar capital program to upgrade the system, with crews replacing about 15 miles of old pipes in the city per year, according to the agency.