The joint that failed on the Richmond-San Rafael Bridge last week showed signs of trouble last summer, but inspectors found no “signs of deficiency” when they checked it in August, NBC Bay Area’s Investigative Unit has learned.
The failed deck joint is among 62 steel-to-steel expansion joints on the span – a comparatively small number of the more than 800 joints that make up the 4.5 mile bridge, authorities say.
Ninety percent of the joints were replaced when the span was retrofitted in 2005, but the steel-to-steel joints were kept and are now more than 63 years old.
The type of joint that failed relies on two steel plates that are embedded into the end of concrete road deck sections with steel studs. Some of those studs may have broken when part of the upper concrete deck fell onto the lower deck.
The joint’s overlapping steel plates are designed to allow for heat expansion and contraction between deck sections.
It was those plates that had been heard to rattle back in August when trucks drove over them at the exact location that later failed.
Authorities say that Caltrans dispatched a crew to inspect the joint both from the top and the bottom, but those inspections did not show any signs of cracking or other issues that could explain the rattling sound.
From the lower deck, all that is visible at the bottom of the upper deck is concrete and drainage gutter. From the upper deck surface, all inspectors can see is the steel plate itself.
Upper deck joints are not easy to inspect from below – requiring a bucket truck -- and the lower deck inspections may require boat access.
Caltrans spokeswoman RocQuel Johnson said the deck joint that failed had “otherwise performed well and had shown no signs of deficiency in recent inspections.”
She noted that 90 percent of the bridge deck joints had been replaced back in 2005, but they “were different kinds of joints than the joint that experienced spalling last week.”
Despite what sources said about the clanging noise triggering the inspection, Johnson said the inspection was routine and not brought on by anything unusual.
Officials involved in overseeing Bay Area bridges said they have a $20 million fund to do an assessment of the Richmond-San Rafael span.
“This was not one of the joints that had been identified for future repair or replacement,” said John Goodwin, spokesman for the Metropolitan Transportation Commission, which operates the local bridge toll authority.
Caltrans’ Johnson says there is, as of yet, no immediate timetable for repairs and lane closures at this point.