Dramatic plans for California’s longest-ever tunnel revealed — as $3.5B project poised for beauty spot

See more of our coverage in your search results.

California’s longest-ever tunnel has been revealed in dramatic new images after being brought in to bypass a landslide-plagued beauty spot.

The 6,000ft “Last Chance Grade” along Highway 101 in Del Norte County will be the biggest underground road passage in the state’s history when it is completed.

The route through the hillside has been specifically picked to avoid as many as four active landslide complexes and shifting earthflows.

Caltrans was holding an open house on Tuesday to allow the general public see the designs and listen to a panel of experts.

The proposed tunnel plan, approved in 2014, will go between Crescent City and Eureka, which serves as the primary route linking Southern California to Oregon and beyond.

But the roadway has faced decades of ongoing disruptions caused by active landslides, sheer oceanfront cliffs and winter storms.

Authorities said that the subterranean alignment will reduce recurring emergency repair costs, vehicle operating expenses, and highway noise within Redwood National and State Parks, which draw roughly 2.5 million visitors each year.  

“Since 1997, landslide repair projects have cost over $100 million when including the estimated costs of the current ongoing work,” the project’s official website said.

According to the official project timeline, the tunnel’s final design work, property acquisition, and environmental permitting will continue from 2026 through 2031, and construction is currently anticipated to begin in 2031.

The completed bypass is scheduled to open to traffic by 2039.

“Last Chance Grade is more than a highway—it is a lifeline for the people, businesses and emergency services of California’s North Coast,” Caltrans Director Dina El-Tawansy had said in a statement in August. 

El-Tawansy added that “advancing this tunnel into the design phase brings us closer to providing the safe, reliable connection Del Norte County and travelers deserve.”

The overall construction cost for the project is expected to be between $2.5 billion and $3.5 billion. Caltrans has not yet secured funding for the building phase. 

Officials also anticipate that the construction phase of the project will generate temporary regional employment across heavy civil earthmoving, underground tunnel support, materials hauling, supply logistics, traffic management and environmental restoration.

---

Download The California Post App, follow us on social, and subscribe to our newsletters