The California Department of Transportation's (Caltrans) emergency $110 million Westport Landslide Complex project is not only repairing the damage caused by landslides to a 1.3-mi. section of State Route 1 (SR 1) in Mendocino County but also is improving the infrastructure to prevent and minimize damage from future storms.
The damage resulted from the winter storms of 2022- ‘23.
"A series of severe winter storms and atmospheric river events brought persistent heavy rain and high surf," said Manny Machado, a Caltrans District 1 spokesperson. "Landslide movement at Westport accelerated, resulting in roadway settlement of over 6 vertical feet. An emergency project was initiated with a project scope to extend the retaining wall to the north, a large-scale geotechnical investigation, coastal revetment, dewatering and roadway reconstruction.
"The Westport landslide is a large, complex and deep-seated slide. The size, depth and many factors contributing to the slide movement make it a challenging location to maintain Highway 1."
Caltrans photo
Myers & Sons Construction initiated operations in March 2024, aiming for December 2026 completion.
The project's scope — along a stretch of the coastal highway with a steep slope of 250 ft. above the Pacific Ocean and a steep hillside peering over the two lanes and inland shoulder lanes — is immense.
Crews have completed a geotechnical investigation and monitoring and are now extending the existing northern soldier pile ground anchor (SPGA) wall, placing a rock revetment at the top of the slope and installing horizontal drains.
The geotechnical monitoring determined that installing a subsurface drainage system (to slow landslide movement), adding retaining structures and performing a revetment to reduce coastal erosion was required.
The landslide width at the roadway elevation is approximately 1,400 ft. In addition to the landslide, a series of nested landslides encroaches on the roadway from below, triggered by wave action and coastline erosion.
"This landslide complex has a long history of movement, resulting in damage to the roadway prism and sometimes long-term lane closures while emergency repairs are undertaken," Machado said. "Without additional stabilization measures, future storm events are expected to contribute to additional roadway loss. Stabilization of the roadway is important because SR1 is a minor arterial route that provides mobility and access to the cities and unincorporated communities along the Mendocino coast."
The project was designed by a multidisciplinary Caltrans project team, along with the Michael Baker International coastal engineering team.
Myers & Sons Construction photo
"The scale and complexity of the Westport landslide make it a very challenging location," Machado said. "Designing and constructing roadway repairs on an active landslide is challenging. … The anticipated maintenance interval of the project is 26 years, given the current rate of slide movement. The rate of movement is anticipated to slow upon completion of the coastal revetment and dewatering system."
Directional drilled subsurface drains are being designed. These drains will be installed behind the slide surface to reduce the groundwater entering the landslide.
Despite the many challenges, Myers & Sons said it is making progress.
"We're working around archeological and environmental issues to access the beach," said Kurtis Frailey, Myers & Son vice president. "We had to build a separate access to it. We're putting 8-ton boulder riprap on the beach to build a revetment. Some of the logistical challenges are finding quarries that can supply the amount of rock that we need. We've had to go to Papich in the Central Valley to get these boulders. There are not many that can provide 1,200 tons a day."
From the west side of the road to the beach is a 200- to 250-ft. nearly straight drop.
"Access at this level has been one of our biggest issues," Frailey said.
Aside from the geotechnical investigation, crews have placed dewatering wells to remove some of the water from the hillsides and have nearly completed the beam and lag wall and 40 percent of the revetment. That involves digging a trench on the beach, then stacking the 8-ton boulder riprap 60 to 80 ft. up.
"It's an active landslide area, so Caltrans wanted to understand the composition of the slides," Frailey said. "It's water that caused the slides — when it builds up, it's most active. Usually in the slide areas, there is a high water concentration."
The geotechnical investigation and monitoring were crucial to determining the number of tiebacks to be placed for the beam and lag wall.
"We ended up with seven rows," Frailey said. "We had to go with sister beams for the tiebacks, which are two big steel beams that end up being the posts that you drill down on the sides. The challenge on the north coast is getting equipment and materials in. We brought in shorter beams and welded them together because of the length restrictions we had on Highway 1. We brought in a large Komatsu 890 excavator, and it was very challenging to get the pieces and parts to put it together on site."
The extension of the existing northern soldier pile ground anchor (SPGA) wall (lag and beam wall) should be completed in September.
"Once we had the design, we started working our way from north to south, placing beams about every 7 feet going downwards. We had to excavate and build access to the steep slope and then excavate again to reach the next set of waler tiebacks," Frailey said. "We are down to the last walers. We're protected by the road, but we have to keep half that road open.
"We're always monitoring for falling debris and rock. We have slides and we have a lookout guy. We had to punch in an access and then build a hand and guardrail to keep the guys safe. We had some handrail on the outside edge and down to the beach. It's a 0.5 to 1 steepness, which is nearly straight down."
The road in this section is approximately 34 ft. wide, and some of the guardrail was falling off on the west side.
Caltrans photo
"We had to make access about 12 ft. below to make an access pad and then work our way down to the ocean," Frailey said. "We had to sink the sister beams. Drill Tech Drilling and Shoring drilled some of the holes. Some of the holes were unstable, and we had to stop drilling. We then poured some concrete and redrilled through them."
Myers & Sons also has done some road work, including grinding and patching.
"It's probably slid down 3 feet since the 1.5 years we've been there, "Frailey said.
Materials-wise, this work is using wood lagging, metal beams and concrete and asphalt. For the revetment, it's a combination of 8-ton riprap boulders and 6-inch riprap for the topping.
Large Komatsu PC900 and Hitachi 872 excavators are among the heavy iron being used for the wall.
Approximately 40 percent of the rock revetment has been placed. Before that work could begin, bringing equipment down to the beach was the challenge.
"We reach the beach where the road drops down to it, then we drive north along the beach for about 1,000 feet and start placing the boulders," Frailey said. "Each flatbed can carry two to three boulders which are placed by an excavator. We work when the tides are low, so we have some early morning work. We may start as early as 3 a.m. because when it is high tide, the ocean rises up against the revetment. We are placing the boulders so fast that our suppliers can't produce them fast enough."
Thumbs are being attached to the excavators, which is unusual.
"They are usually not on excavators, and they were difficult to find," Frailey said. "We had to order in advance to place them and grind the rock."
Myers & Sons has avoided equipment being caught by rising tides.
"We have plans in place in case a piece of equipment breaks down, to bring it out," Frailey said. "We have a big dozer on standby to drag it off the beach. With the Coastal Commission and environmental regulations, we can't have equipment out in the ocean as the tide rises."
The subsurface drainage system installation to slow landslide movement and additional retaining structures will begin once the revetment is completed.
"We're installing a couple of thousand feet of … horizontal drains — lowering them to the side to relieve some of the water pressure," Frailey said.
The installation plan will likely be based on a directional boring rig with a perforated casing and a directional horizontal drill rig.
"This won't be easy," Frailey said. "We'll wait for the design and then get our plan of attack. We've installed vertical drains but not horizontal ones."
Myers & Sons Construction photo
Myers & Sons' management team consists of Project Manager Chris Nelson, General Superintendent Scott Wilson and Superintendent Ross Patterson.
"It's a good team dynamic," Frailey said. "They've been working together for years and have 10-plus years' experience with the company. They work very collaboratively together and efficiently. …
"The crews have been great. A lot of them are from far away and working out of town every week. They stay diligent and work safely. We've had zero incidents on the job for safety and zero recordables."
The crews are being housed in rented homes and, occasionally, in motels.
Typical days have 25 to 30 Myers & Sons and subcontractor personnel on site. Local subcontractors and suppliers include Wylatti Resource Management, Geo Aggregates, Northern Aggregates, LD Giacomini Enterprises and WIPF Trucking.
Looking after its equipment is a must for Myers & Sons.
"It's a salty environment and it takes its toll," Frailey said. "We maintain, grease and lube all the time to make sure we're rinsing it off. The big rocks we are hauling in are rough on the equipment. We've had to make some adjustments on the thumbs on the excavators to the pressure from the weight of the big rocks. We have an on-site mechanic."
