A water main break flooded part of the Treasure Island tunnel on the San Francisco-Oakland Bay Bridge today, shutting down two eastbound I-80 lanes and turning the evening commute into a soggy mess. Water covered portions of the roadway and choked traffic inside the tunnel while Caltrans and San Francisco Fire Department crews moved in to manage the runoff and inspect the pavement. Officials did not immediately say when the closed lanes would reopen.
Officials' Alerts and Response
The California Highway Patrol issued a traffic alert on X, noting that the No. 4 and No. 5 eastbound lanes of Interstate 80 inside the Treasure Island tunnel were temporarily closed because of flooding. The alert urged drivers to expect delays and use extra caution in the area, as shown in a post from CHP San Francisco.
***TRAFFIC ALERT on I-80 e/b***
— CHP San Francisco (@CHPSanFrancisco) April 21, 2026
Due to water main break above, the #4 & 5 traffic lanes of I-80 e/b (SF/Oakland Bay Bridge) in the Treasure Island tunnel are temporarily closed due to flooding. Caltrans & SF Fire are currently on-scene attempting to resolve the incident. pic.twitter.com/Oefx5VkWmy
Crews on Scene and Traffic Updates
Caltrans crews and the San Francisco Fire Department were reported on scene working to pump out water and assess any damage, and officials said there was no immediate timetable for reopening the flooded lanes. Drivers were urged to plan for delays and consider alternate routes while the No. 4 and No. 5 eastbound lanes remain closed, according to NBC Bay Area. Motorists can check real-time conditions through the Caltrans 511 system for the latest updates.
Why Treasure Island's Water Mains Matter
Treasure Island gets both drinking water and firefighting water through transmission mains that run across the Bay Bridge, a setup documented by the San Francisco Public Utilities Commission for the island’s utility system. The SFPUC project factsheet notes that when infrastructure on the bridge is damaged, it can complicate repairs and emergency water access for the island.
Officials said they would provide more information as crews secure the scene and complete repairs. We will update this story when agencies release new guidance for drivers and island residents.
