Water main break floods Treasure Island tunnel, closes Bay Bridge lanes

Water poured into the Treasure Island tunnel and forced the closure of eastbound Bay Bridge lanes just before 1:45 p.m. Tuesday, disrupting one of San Francisco’s most important commute routes at the height of the day.

The California Highway Patrol said the rupture happened on the eastbound side of the San Francisco-Oakland Bay Bridge, inside the Treasure Island tunnel, and flooded lanes No. 4 and No. 5 on eastbound I-80. Caltrans and the San Francisco Fire Department responded to the scene as crews worked to remove water from the roadway and restore traffic flow.

NBC Bay Area later reported that all lanes had reopened after the water was cleared, though it was not immediately clear how long the closures lasted. Even a short shutdown in that corridor can ripple quickly through the Bay Bridge approach, where thousands of drivers depend on the span to move between San Francisco, Treasure Island and Oakland.

The break also drew attention to the condition of the city’s water system. The San Francisco Public Utilities Commission says it maintains about 1,200 miles of water pipelines in San Francisco, and roughly 20% of those pipes are around 100 years old. The utility also says it sees between 100 and 200 water main breaks a year, a reminder that failures like this are not isolated glitches but part of a larger infrastructure burden.

That burden is especially significant around Treasure Island and Yerba Buena Island, where the city’s long-range development plans call for as many as 8,000 homes, with about 27% set aside as affordable housing. As the area grows, the reliability of the tunnel, bridge approaches and buried utilities will matter even more to daily life, emergency access and the region’s commute network.

For now, the flooding was cleared and traffic resumed. But the episode left a familiar San Francisco question hanging over the Bay Bridge corridor: how many more times can an aging system fail before the cost shows up not just in repairs, but in the city’s daily movement itself?