SAN MATEO (CBS/AP) — People who use the Dumbarton Bridge to get across San Francisco Bay will have to find an alternate route during the holiday weekend. The entire Dumbarton Bridge is closed over Labor Day weekend to complete another major element of the seismic retrofit project.

The closure began late Friday and will end as late as 5 a.m. Tuesday.

Over the three-day closure, Caltrans will replace the expansion joint on the eastern side of the bridge across all six lanes of traffic.

During the closure, motorists are encouraged to take public transit or alternate driving routes. Motorists should allow extra time for travel and use other bridges, including Highway 237 and Hwy 92 via the San Mateo Bridge.

Caltrans officials say the work being done this weekend keeps the retrofit work on track to be completed by early 2013.

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