The slide happened around 10:30 a.m. "Half of the hillside collapsed and fell into the northbound lanes of Highway 17," a California Highway Patrol Officer Trista Drake said.
TRAFFIC: See current road conditions and closures
The driver of the truck was able to walk away. There was no estimated time when the other lanes would reopen.
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Tuesday's slide happened in the same area where a slide in January that crushed a news van, sending a photographer to the hospital.
The upgrades Caltrans put in place after that slide couldn't hold back the tons of mud and debris that slid into the road Tuesday. "They thought they had it under control with a barrier there, but it just couldn't handle the amount of material that came down," Gary Peters told ABC7.
Highway 9 and other roads drivers use when Highway 17 is closed were also impassible due to flooding.
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CALTRANS working through the night tonight hoping to open at least some lanes tomorrow on Hwy 17. pic.twitter.com/xo6AcMkBWV— Vic Lee (@vicleeabc7) February 7, 2017