GLEASON BEACH – It will be a few years before motorists can take the prescribed new route of Highway 1 on the south Sonoma coast – a three-quarter-mile stretch of road that has been under construction since late summer.

But steel and concrete pillars erected in recent months to support the deck of the bridge to be built next spring already demarcate part of its path, as it plunges inland, curving up to 400 feet from where the existing highway hugs the crumbling coastline.

Caltrans and other state officials say the realignment of more than $ 30 million is a critical step in protecting the state’s Scenic Highway from rising sea levels and storm surges.

They say it’s the first of what will likely be many future adaptation projects in various areas of Highway 1, though perhaps none is as urgent.

The cliffs along parts of Highway 1 between Jenner and Bodega Bay lose up to 14 inches per year due to waves and seepage. Authorities believe this is the fastest rate of coastal erosion in all of California.

Waves had plagued the landscape for more than a decade when the problem suddenly gained public attention in 1998, in a series of torrential storms that undermined the cliff face and destabilized several houses at the top, rendering some uninhabitable.

Over the years, the cliff has continued to disintegrate, despite substantial investments in concrete dikes and ramparts by several owners.

Erosion quickly threatened the highway, eventually eating away at the asphalt edge. Caltrans attempted to reduce the risk to southbound motorists by shifting the lines and eventually abandoning the failing westernmost lane, which began to sag and crack as the ground below became unstable. A second lane has been added inland.

But the deterioration of the coast is only expected to accelerate. According to the project’s environmental impact report, the rising ocean and increasing wave action are expected to remove about 1.5 feet of land per year from the region by 2050 and 4.6 feet per year. year by 2100.

Caltrans is moving the highway far inland to stay ahead of long-term erosion in an approach known as “managed retreat”.

Calling sea level rise “the biggest problem of the 21st century, acting chief engineer of Caltrans, Nabeelah Abi-Rached, said at an official launch of the Gleason Beach project last month that it was only the first that the agency would set up to solve the problem.

“The rising waters that threaten Highway 1 here also threaten the highway in many places along the coastline,” said Abi-Rached, “but we’re tackling it first. I want to stress that this work is unprecedented.

The extreme deterioration is complicated by the terrain. It starts at the north end at the top of the cliff, then plunges down to the outlet of Scotty Creek and the surrounding floodplain before moving up to the south side of Scotty Beach. The task is to elevate the road above the salmon stream and adjacent sensitive habitat, in addition to moving it inland.

The final project, in the planning and licensing phase since 2007, will include an 850-foot-long bridge that will be the largest man-made structure on the Sonoma Coast, taller than some coastal residents had hoped.

But the overall approach of the project is multifaceted and is the result of years of negotiations and accommodation which will also result in some compensation. Among them, the natural lighting of Scotty Creek, now confined by a box culvert, improving fish passage; cleaning up concrete and construction materials that fell to the base of the deteriorating cliff, where at least 12 houses have fallen or have been removed since 1998; and improving public access to popular Scotty Beach.

Sonoma County is the birthplace of enabling legislation from the California Coastal Commission, which granted the permit for the project to continue. At the inauguration, the commission’s executive director, Jack Ainsworth, said the project “represents this bridge to a more resilient California.”

“This beautiful stretch of coast needs to be handled with care, and I think we did that with this project,” he said.

Construction began unannounced on August 20 and ended for the season on Saturday. It will be April 15 before work can resume due to regulations surrounding wetlands, said Fabio La Serna, assistant resident engineer at Caltrans.

Parts of the project that encroach on wetlands will continue seasonally until the entire realignment is completed in late 2023, or possibly early 2024, La Serna said.

In the spring, construction crews will begin “a massive earthworks operation” to prepare the new route of the motorway, as well as the construction of the bridge deck, for which some support materials were positioned last week, Fabio said. .

The huge construction site was in turmoil, with huge cranes, a concrete pump with a large boom, and other heavy equipment moving over a wide area. The wetlands were covered with 3-inch mats and rocks to help distribute the weight, La Serna said.

Cattle grazed in a bright green pasture directly in front of a site wildlife fence, seemingly sheltered from the noise and bustle.

At the mouth of Scotty Creek, across the highway from Scotty Beach, now part of Sonoma County State Parks, three people stood guard, surveying archaeological sites left behind by residents of Pomo and Coast Miwok 11,000 years ago.

One of them, David Carrio, a tribal cultural monitor with the Federated Indians of Graton Rancheria, said they wanted to not only protect ancestral remains that might surface during construction, but also keep artifacts buried over time on land that had provided food, medicine, and an obvious place for fellowship and play in the past.

“It was our special place,” Carrio said. “A lot of people come to this beach and fall in love with it. They say, ‘This is our beach.’ It makes you proud.

More about the project and a 3-D graphic can be found at gleasonbeachrealignment.org.

You can reach editor Mary Callahan at 707-521-5249 or [email protected] On Twitter @MaryCallahanB.