The debris slid well out into the ocean, creating 15 acres (6 hectares) of new coastline about 9 miles (14.5 kilometers) north of the Monterey-San Luis Obispo county line.
The transportation Department has since been working to stabilize the slide to rebuild the highway over it. The $54 million project included building a massive rock seawall at the foot of the slide.
This strategy is allowing roadway rebuilding more quickly and at a lower cost than other alternatives such as structures, a tunnel or major earthwork that puts additional fill into the ocean, the transportation department said.
The work is being done about 25 miles (40 kilometers) south of where another segment of the highway was blocked when a storm-spawned landslide wrecked a bridge in early 2017.