Forget about the new span's many, many troubles, there is now a new clear and present danger in one of the older parts of our main artery across the Bay, the Yerba Buena Island tunnel. As the Chron reports via a report from Caltrans, a sizable chunk of the tunnel's concrete arch came crashing down on an unsuspecting Ford Fusion two Saturdays ago, and this could mean that the 80-year-old tunnel has some serious, unforeseen structural problems, possibly from water damage.
The three-inch-thick piece of concrete was about two and a half feet square, and fell right into the southern (left-hand) eastbound lane on the afternoon of January 30, scraping up that car and causing it to blow a tire when it ran over the thing. This was about a third of the way into the tunnel where further cracking and water damage looks to exist that is "obscured by the tunnel ceiling," per the Chron. The tunnel was last inspected in July, and no problems were detected.
Says Caltrans Deputy District Director Dan McElhinney, "Safety is first for us, so this was not a good situation at al. We are lucky that it wasn’t more severe." He adds, "These are opportunities to figure out what is going on with our aging infrastructure. [And] This wall has seen many, many years of service."
Interesting trivia, though: This tunnel, which may not seem so impressive to laymen, is the largest, longest single-bore tunnel in the world, with its two levels, five lanes across and 1800 feet in length. It was completed in 1936, the year before the bridge opened.