Crews Work to Stabilize U.S. 101 After Dangerous Collapse

Tue April 06, 2021 - West Edition #8
Lori Tobias – CEG Correspondent


Crews installed new guardrail and filled an 8-in., 2-ft. deep hole between the new retaining wall with gravel. That portion will be paved later in the spring. The collapse at milepost 170.5 has underscored the need to keep a close eye on the historic highway, and inspections along the 360-plus miles of highway will no doubt be ramped up in coming months. The Oregon Department of Transportation contracted with GeoStablization International (GSI) to stabilize the area.

A much traveled piece of the Pacific Coast Scenic Byway is open to travel again after a potentially tragic accident closed it in February. Repairs are expected to continue through spring.

Oregon's historic oceanfront highway is a much-loved travel route along the state's coast, but it's also vulnerable to numerous instabilities, such as the collapse at a wayside known as Bray's Point. The disaster at milepost 170.5 plunged a drill rig and its operator 150 ft. to the rocks below, and served as a reminder that this climbing, curving scenic road is not the usual drive.

"U.S. 101 is an aging, unstable road on many parts of the coast and so our maintenance crews are constantly responding to various slides, sink holes and cracks in the road," said Angela Beers-Seydel, spokeswoman of the Oregon Department of Transportation (ODOT). "This started out as somewhat typical of life maintaining that road. A maintenance crew member saw a new crack and went to investigate. They were really concerned since we hadn't seen issues at Bray's Point before. It cracked more and our geo/hydro engineers were brought in to find out why. They found and assessed the crack in the historic retaining wall and recommended that the section be shored up immediately."

ODOT contracted with GeoStablization International (GSI) to stabilize the area. GSI brought in its own heavy equipment and went to work.

"This is what GSI specializes in," said Beers-Seydel. "Since 2002, they've done 4,791 projects, including dozens of rock wall repairs and thousands of emergency slope stabilization projects. They said nothing like this has happened before. It was shocking to them, too."

Crews initially focused on stabilizing the area to ensure the safety of workers and motorists traveling through the area.

But the window for repair wouldn't last. Only five days into the fix, the southbound lane collapsed. The drill rig operator survived – some would say miraculously – with only minor injuries, but the highway was closed. Days later, Mast Brothers, a towing firm based on the central and south coast, brought in three semi-tow trucks to retrieve the drill rig.

With the drill rig recovered, GSI crews then went to work installing a combination of micropiling and soil nails.

"Soil rods vs. micropiling, it's all part of the same idea," said Beers-Seydel. "You've got these pieces of metal that take the force off of the earth to hold it in place. Fortunately, the remaining wall was intact and none of the vertical rods already placed had moved or were damaged, so they were the foundation for the rest of the work ... We added horizontal rods after the failure through the exposed soil and the remaining wall, and continued the installation of the vertical rods. These now disperse the earth load of the fill, lessening the direct pressure on the wall area. Then the entire wall – new and repaired – was covered with concrete to reinforce the slope, holding the fill under the road in place for the long-term. In effect, the existing wall becomes a facade and the micropiles are doing the work of supporting the road way."

Crews also installed new guardrail and filled an 8-in., 2-ft. deep hole between the new retaining wall with gravel. That portion will be paved later in the spring when the weather – notoriously wet and windy in the winter months – calms in the spring. The highway will be reduced to one lane for paving with flaggers controlling traffic at that time.

ODOT initially budgeted for $200,000 to $250,000 to fix the wall, but once it collapsed, that cost nearly doubled to $450,000.

"When the wall unexpectedly collapsed, it was a worst nightmare," said Beers-Seydel. "Crews are constantly telling me that they love working on the coast because of its beauty, but they recognize the inherent danger of working on a narrow road with ancient slides, blinding rain and ever increasing traffic. They are careful in where and when they work, planning for the worst, mitigating the danger as best they can, and normally keeping everyone moving without having to think about the route beyond the stunning view."

The collapse at milepost 170.5 has underscored the need to keep a close eye on the historic highway, and inspections along the 360-plus miles of highway will no doubt be ramped up in coming months as noted in a memo from ODOT geotechnical engineer Tony Robinson.

"The as-built condition of this wall is an example for how to work with the remaining rockery walls of similar ventures along US 101," Robinson said. "Similar plans should be made immediately for supplemental shoring to the highway as it's prudent to assume other walls of this vintage and in this area may well have similar construction deficiencies." CEG




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