Mud Creek landslide adds at least a year's delay to Rt. 1 reopening

May 25, 2017

The Mud Creek Slide is being called the biggest landslide to hit the Central Coast, at least in recent memory. On May 20, millions of tons of rocks and dirt collapsed over Route 1 when four separate, adjacent slides triggered at the same time, combining into one massive terrain avalanche.

Mud Creek is located eight miles north of Ragged Point, the northwest tip of San Luis Obispo County. Hwy. 1 has been closed at Ragged Point to Big Sur-bound traffic for months, so no one was hurt when the slide occurred. A quarter-mile stretch of the two-lane highway now lies under a solid wall of dirt, 40 feet high.

On Thursday, Caltrans invited local media on a tour of the slide area. It is an awesome sight, an entire mountainside crumbled into the sea. Caltrans engineer Rick Silva pointed to the new shoreline, an estimated 16 acres that wasn't there on May 19. Silva described the prelude to slide.

“For the three weeks before this, it was pretty active, it just kept getting worse every day, we kept losing more and more of the road,” Silva said. “We had a construction operation going on, so by the week before it happened, we pretty much cancelled all construction work. We were just backing off and getting out of here. And then, I think our last day out here was Thursday or Friday...and then Saturday it went.”

Caltrans spokesperson Susana Cruz said it’ll be a while before engineers can spend time on the slide to figure out a repair solution.

"It’s millions of cubic yards, so you can imagine, there’s a lot of rumbling. And actually if we hike up a little bit, you might hear a little bit of the rock fall,” Cruz said. “It’s still active, so that’s the reason it will take several weeks for us...we can’t really be up there, because it’s still moving.”

The key question asked of Cruz during the visit was, how long will it take to fix it? 

“It is going to take approximately a year,” Caltrans spokesperson Susana Cruz said. “We have to see if there’s any roadway underneath here, which we feel it might be gone. Just several weeks of being able to assess, design and get an idea of what the fix will be.”

Wade Hoon, part of a team taking soil samples near the slide this week, works for the engineering firm Yeh & Associates; previously he worked as a Caltrans engineer from 1991 through 2010. Hoon said in all his time working on California’s coast, the Mud Creek slide is the biggest he’s ever seen. He also said it was a unique learning experience.

“I spent my whole career doing this, drilling and logging holes. And then to see a big failure like this and to see how all the material come down helps me characterize what I’m drilling through now,” Hoon said. “I mean, I’ve drilled through the results of these slides but I’ve never actually seen one happen.”

He said from now on, he’ll be able to more clearly distinguish the particular position of soils involved in past landslides, whether the soil came from the top part that dropped down intact or part of the advancing base that churned as it flowed.

Cruz compared the Mud Creek slide to one that occurred near Julia Pfeiffer Burns State Park in 1983, saying the Mud Creek slide was larger. It took 14 months to repair the highway after the 1983 slide, said Cruz, adding that at this early point, Caltrans doesn't have a firm estimate of how much time and money it will take to restore California’s scenic highway along the Central Coast this time around.