RICHMOND (CBS SF) — Engineers overseeing the emergency repair of a failed expansion joint on the Richmond-San Rafael Bridge that sent debris tumbling down onto the lower eastbound lanes have determined that an additional 31 joints now need to be replaced, Caltrans announced Friday.

Contractors have been working overnight this week to replace the failed upper-deck joint that sent large chunks of concrete tumbling onto the lower deck, damaging at least one car on the morning of Feb. 7.

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The debris fall forced the vital transit link between the East Bay and Marin to be shut down for several hours, triggering a commuter nightmare. Initially, crews were only going to replace the one joint, but inspections have revealed wear on the others.

“Safety is Caltrans’ top priority,” said Caltrans District 4 Director Tony Tavares. “Out of an abundance of caution, we decided to replace the remaining sliding plate joints on the bridge beginning with those on the upper deck.”

Tavares added that “engineers perform regular inspections of the bridge and have reinspected all joints on the bridge in recent weeks. The bridge remains safe and open to the public.”

Caltrans said that in the early 2000s, more than 90 percent of the bridge’s 856 deck joints were rebuilt as part of the seismic retrofit or through other rehabilitation projects.

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It was determined at the time that the remaining 61 joints, different types of joints called sliding plate joints, did not need to be replaced. The remaining 30 joints on the lower deck will be replaced as part of an upcoming rehabilitation contract later in 2019.

The most recent inspection of the underside of the upper deck and the upper deck joints was conducted in August 2018, the state transportation agency said. The last inspection of the driving surface on the upper deck was completed in September 2017.

“Structural integrity issues were not identified in any of the last inspections,” Caltrans said in a news release.

Replacement of the joint at Pier 59 that experienced failure earlier this month was expected to be complete by Saturday, March 2. Nearly identical work on the 31 additional upper deck joints was scheduled to begin March 4.

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Caltrans said crews would begin installing temporary steel plates on the upper deck roadway at these locations on the night of Feb. 25. Work will take place overnight from 9 p.m. to 5 a.m. and one lane of traffic will remain open in each direction.