Caltrans faces a wild card as it works to rebuild Highway 1

Mother Nature is always the wild card when it comes to keeping a highway open in steep terrain, but storms this winter could do more than cause new landslides along the Big Sur stretch of Highway 1, Caltrans officials told North Coast business leaders Tuesday, Aug. 15.

Heavy rains also could halt ongoing work to reopen the highway where crews are working dawn-to-dusk seven days a week to create new roadway over a huge slide area that landed where the old highway used to be.

This year, Highway 1 has been closed to through traffic north of Ragged Point, with earth movement in three key spots being the most troublesome — Pfeiffer Canyon (45.5 miles north of the county line), Paul’s Slide (21.6 miles north) and Mud Creek (8.9 miles north).

Caltrans still doesn’t have a scheduled reopening date or estimated cost for the road-rebuilding project at Mud Creek, the officials said.

The closures have been worrisome for the state road agency, area residents, travelers and the businesses that serve them.

A replacement bridge is being constructed at Pfeiffer Canyon, and the Paul’s Slide area has reopened with limitations.

But the monster mess is at Mud Creek. With more than 5 million cubic yards of material having slid down the mountainside, especially on May 20 and since, the Mud Creek slide “blows away anything we’ve seen before” along the Big Sur stretch, Caltrans spokesman Colin Jones told members of the Cambria Chamber of Commerce Board of Directors Tuesday. Jones is public affairs manager for Caltrans District 5.

At Mud Creek, huge, soggy slopes buried part of an internationally beloved route along the Pacific, and land movement for months created new acreage beyond the original shoreline.

Post-slide, a newly created point “extends 550 feet out into the ocean,” Joe Erwin, Caltrans project manager at Mud Creek, said, and it added 2,400 feet of new shoreline. “It’s so massive, it’s hard to even grasp how big it is.”

He described a landslide in human-body terms, with a toe on the bottom into the ocean, the body of the slide in the middle, the head of the slide and an “exposed scarp” area above that.

Erwin said that while there’s still some movement at the scarp, and wave-action erosion at the toe has chewed away about 100 feet there, complex engineering studies show the body and head of the slide are well packed, stable, solid and secure.

That’s where the new road will go.

Erwin explained the differences between the current situation and how the agency handled a previous slide south of Julia Pfeiffer Burns State Park in 1983-84.

According to a Caltrans history, that slide “was at the time the largest slide to affect a state highway; it took over a year to completely clear that slide and reopen the road between Big Sur and San Simeon.”

To do so, Erwin said, contractors with 20 dozers started at the top of the slide and, working their way down the slope, cut into the landslide material and pushed it into the sea.

The emergency project caused environmental impacts to marine life, the sea floor and a kelp bed in that area, he said. Now, “biologists are telling us that some of those areas haven’t come back, and may never come back.”

A couple of decades later, Caltrans adopted a management plan for the Cambria-to-Carmel stretch of Highway 1, which Erwin called “a ribbon of highway going through the coastline and the ruggedness of Big Sur.”

The plan outlined changes in how Caltrans would manage the highway, he said, acknowledging that “instead of moving mountains, we’re living with landslides.”

Erwin said the plan gave four options for situations such as the Mud Creek slide:

1. Protect the highway, as Caltrans did last year with preventive netting placed at Cow Cliffs to keep rocks from falling on the roadway.

2. Manage a slide, such as using loaders to do work to keep material in place until it can be hauled away.

3. Relocate the highway.

4. Stabilize the surrounding terrain.

Options 3 and 4 are the ones that apply to Mud Creek, he said.

Crews are stabilizing the support bluff areas, especially with berms at the head of the slide, and in the sections where the new roadway across the stable body of the slide will connect to the existing highway.

The finished terrain will look similar to the Duck Ponds area, just south of Mud Creek and about 9 miles north of Ragged Point, Erwin said, where the highway was constructed “on a landslide that happened about 500 years ago.” That slide was similar to the Mud Creek event, he explained.

But why not build a tunnel? Time and money are prime factors, he said. It took decades to plan and construct the new Devil’s Slide tunnel north of Half Moon Bay. “A tunnel doesn’t fit the situation at Mud Creek. Maybe in the future … there or in another location. But not now, “realigning is the only option we have.”

By relocating and stabilizing, he estimated that Mud Creek repairs would cost less and create less environmental impact than the old bulldozer cut-and-scrape process, and the highway would be able to reopen sooner … if Mother Nature cooperates.

Not only does rain itself stop the project for a time, in many cases, crews must wait to resume work until the soil drains and stabilizes.

“If we have another winter like last year, we can’t work,” Erwin said. “That is the wild card.”

This story was originally published August 16, 2017 at 10:09 AM with the headline "Caltrans faces a wild card as it works to rebuild Highway 1."