An ABC7 News crew captured it live on the air. Reporter Cornell Barnard was live during our morning news when he heard a rumble and the CHP told him to get out of the way.
The boulders damaged but there weren't any serious injuries. The rockslide happened in the southbound lanes of Highway 101 in Sausalito, just south of the Waldo Tunnel.
A damaged retaining wall marks the spot where a rockslide crashed down onto the highway around 4:45 a.m.
Three cars were damaged. The worst happened to a Mercedes SUV that hit the boulder head on. The male driver was taken to the hospital with minor injuries.
Katie Wheelock says she came out of the Waldo to a highway covered with debris and large rocks, "There was a whole bunch of rock and a whole bunch of debris in the middle of the freeway," she said. "I just nipped one and I got a flat tire and my tires are pretty strong. I mean, there was one that was pretty substantial."
"From what I came to understand the largest boulder was about three feet by three feet," Marin CHP spokesperson Andrew Barclay said. "That's a sizeable chunk of rock to land in the middle of the roadway, which explains the major damage to the SUV that hit it."
Caltrans crews, a contractor and the CHP happened to be working on a project on the opposite side of the freeway, and swooped in quickly to help and clean up. But the hill kept slipping.
The two southbound right lanes were closed for three hours. The two left remained open. The hillside is Caltrans' jurisdiction.
Golden Gate Bridge District spokesperson Mary Currie says the rock slope has been stable for decades, but notes it does have a history of slides.
"The last big incident in that area, and I can't say it was specifically there, but right up there was the floods of '82 and '83 when there were massive slides in the Waldo Tunnel area and the roadway was closed actually for several days," Currie said.
We wanted to check on future plans for securing the roadway but neither Caltrans, nor the Marin supervisor for the district returned our calls.