Caltrans proposes $2.5 billion tunnel to repair final stretch of Hwy 101

California taxpayers are eyeing a multibillion-dollar price tag to rescue one of the nation’s most unstable highways, a crumbling stretch of coastline that’s literally sliding into the ocean.

The California Department of Transportation is now developing a plan to drill a 1.1-mile tunnel through the redwood forest to bypass the crumbling portion of the “Last Chance Mile” on US Highway 101, and the project is estimated at $2.5 billion.

That shocking number comes after more than a decade of research, outreach and planning, culminating in a 712-page environmental impact report that cost $55 million and was released in late May.

Next, Caltrans is expected to ask the California Transportation Commission for $225 million later this summer just to fund the design phase of the tunnel, bringing international experts into the tunnel’s seismic design.

The proposed renovation is aimed at a three-mile stretch of highway in Del Norte County that clings to fog-shrouded cliffs between ancient redwoods and the Pacific Ocean.

Download the California Post App, follow us on social media, and sign up for our newsletters

The route is the only physical road connection between Crescent City, a tsunami-prone city of about 6,000 people, and Humboldt County and the wider region.

When the road is closed, drivers are forced into a brutal 449-mile, eight-hour stretch of Redding and southern Oregon, unless they try the steep, unpaved roads.

Instability is not new.

The tunnel began life as a wagon route in 1894 and was rebuilt in the 1930s, despite early warnings from engineers that constant ground movement would make repairs too expensive.

Those warnings proved accurate.

During construction, “many slipouts and slides occur, delaying construction,” according to a 2015 feasibility study.

Today, the highway sits on four landslides and has become one of California’s most problematic highways.

In the past, it was reduced to one-way traffic for nine consecutive years, reopened briefly in October 2023, and has since experienced repeated restrictions.

The ground beneath it has shifted dramatically, up to 40 feet horizontally and 30 feet since the 1930s, and some parts are now moving a few feet each year toward the Pacific.

Efforts to strengthen it have largely failed.

More than a dozen retaining walls have been built over the decades, but many have cracked or shifted as the slope continued to move.

In 1972, a fall in the pre-dawn hours sent a car over a cliff, killing a married couple.

The country’s solution is a tunnel to the east that would bypass the most dangerous area.

At 6,000 feet, it would be the longest road tunnel in California, surpassing the 4,233-foot Wawona Tunnel in Yosemite National Park.

But the adjustment has environmental consequences as well.

The route crosses Redwood National and State Parks, a UNESCO World Heritage Site, and will require the removal of 16 old redwood trees over four meters wide, as well as additional trees, according to the environmental impact report.

Jaime Matteoli, Caltrans’ project manager for the Last Chance Grade, called the effort a necessary investment despite the magnitude of the challenge.

“It’s a proud moment,” Jaime Matteo, Caltrans’ Last Chance Grade project manager told the Los Angeles Times. “It’s a big quality of life problem for people, who don’t feel safe on that road. It’s obvious that this project is necessary.”

If the funding goes ahead, construction could begin as soon as 2031, with the tunnel likely to open in 2039.