STEVE INSKEEP, host:
It's MORNING EDITION from NPR News. Good morning. I'm Steve Inskeep.
RENEE MONTAGNE, host:
And I'm Renee Montagne.
And we're going to hear, now, the back story to the trouble on the San Francisco Bay Bridge, which has forced the closure of a bridge that carries more than a quarter million vehicles a day - and still closed this morning. More than two tons of metal fell on that bridge during rush hour this week. As NPR's Richard Gonzales reports, problems with the bridge go back 20 years.
RICHARD GONZALES: October 1989, after the Loma Prieta earthquake strikes, a reporter on San Francisco TV station KGO shows stunning pictures of a catastrophe.
(Soundbite of television broadcast)
Unidentified Woman: This is tape right now. This is a taped picture of the Bay Bridge, major section. This is a mile from the toll plaza on the Bay Bridge, just before the superstructure. It has completely collapsed. We had reports that cars were trapped underneath it. If you are anywhere near that location, do not head to the Bay Bridge. It is closed.
GONZALES: The Bay Bridge was built during the Great Depression. Back then, engineers thought it might last forever. But structural engineer, Mark Ketchum, says it won't.
Mr. MARK KETCHUM (Structural Engineer): We look backwards at what was designed at the time and we see that using modern statistical tools and other engineering techniques, we see that they have design lifespans for these major investment toll bridges of about 75 years.
GONZALES: If that's correct than the Bay Bridge, which is now 73 years old, is near the end of its life. And it would've been retired soon after the Loma Prieta earthquake, but it took years for politicians and bureaucrats to decide how to design a replacement and who would pay for it.
Skip ahead now to 2009. A new bridge is being built. But it requires the old bridge to be closed during the Labor Day weekend. That's when officials discover a cracked I-bar beam on the old bridge. Bart Ney is a spokesman for Caltrans.
Mr. BART NEY (Spokesman, Caltrans): So a repair was designed and done over that same time that we had the bridge out of service and put in place. Now, what's happened since then - the problem that we had the other night - is that the repair had a problem itself, not the bridge.
GONZALES: The repair failed, and thousands of pounds of metal fell on the bridge. Fortunately no one was seriously hurt. Officials blame high winds and vibrations created by traffic for causing the system of rods and steel brackets to fail. Now they are tweaking the old repair. But many Bay Area residents and commuters are beginning to voice their doubts that Caltrans, having failed once, will get the repair right this time.
Kavay Rod(ph), a structural engineer, is skeptical. He says there are questions Caltrans hasn't answered.
Mr. KAVAY ROD (Structural Engineer): Why the failure happened. What assurances do they have - do people have - that they understand what caused the failure and that it won't happen again?
GONZALES: Caltrans officials say they won't reopen the bridge until the test the repair in front of federal and outside experts.
Richard Gonzales, NPR News, Oakland.