SAN FRANCISCO (KRON) — The Federal Highway Administration is inspecting the Bay Bridge tunnel through Yerba Buena Island.

They are using ground-penetrating radar to look for any weak spots in the concrete of the nearly 80-year-old tunnel. Back in January, a large chunk of concrete fell from inside the tunnel and nearly hit a driver.

Shortly thereafter, Caltrans did conduct an inspection and found several problems that it has since repaired. The transit agency said that the use of radar for this second inspection could help spot hard to see dangers.

“Sometimes there will be problems that aren’t visible on the outside,” Caltrans spokesman Bob Haus said. “The ground-penetrating radar goes up to 12 inches in. So, it can tell if there’s a problem deep within the concrete that you can’t see from the outside.”

Caltrans said that once this latest inspection is complete, they will review the data and decide if any further repairs are necessary.

They also believe that the tunnel is safe for drivers.