LOS ANGELES — More than two dozen construction workers narrowly avoided disaster Wednesday night when a section of an industrial tunnel under Los Angeles partially collapsed, forcing them to navigate miles of debris and rising water in the dark.

All 31 workers made it out alive without major injuries, according to Fire Department Chief Ronnie Villanueva. “They’re shaken up,” said Michael Chee, spokesperson for the Los Angeles County Sanitation Districts. “All work has been halted and the workers will take time to recover.”

The tunnel — 18 feet wide and stretching seven miles beneath the Wilmington neighborhood north of the Port of Los Angeles — is part of a $700 million wastewater infrastructure project designed to carry treated water to the Pacific Ocean.

On Wednesday evening, the crew was 400 feet underground and up to six miles from the entrance when they detected trouble. They had just spent an hour traveling to the work zone in a transport vehicle to supervise a tunnel boring machine that simultaneously excavates and installs panels to support the tunnel’s walls.

When debris started falling, the workers scrambled onto the transport vehicle, but it could only get them so far before hitting the blockage. “What we understand is the men who were in front of the collapse had approximately 6 to 8 feet of space above the debris where they were able to clamber over,” Chee said.

With water pouring in and the lights out, they continued on foot. Aerial video later showed a crane lifting survivors out in a yellow cage.

Among those rescued were Arally Orozco’s three brothers, who were too traumatized to speak publicly. Orozco recounted that they heard a sudden hissing noise — “like a psss sound, like air was going out, like pressure was escaping” — before debris began to rain down.

“They heard like a psss sound, like air was going out, like pressure was escaping, and they didn’t know what it was,” she said. “He told me he thought he was going to die underground.” One brother described crawling through a tight opening as water surged to his waist and the tunnel seemed to lose oxygen. “They felt helpless,” Orozco said.

Despite the frightening escape, the project had no previous incidents in its two years of operation, Chee noted. “The tunnel boring machine has been digging under streets, public right-of-ways, homes, parks, lakes, ponds, golf courses without incident until now,” he said.

Officials plan a full investigation to understand what went wrong. “Everything from the engineering to the structural integrity to the safety,” Chee said. Maria Mohammed, president of the Structural Engineers Association of Southern California, explained that working deep underground near the coast brings challenges. “You would design not just for the pressure from the soil and the weight of the soil; you have to design for the pressure from the water,” she said.

“It all comes down to: what’s the first element that broke?” Mohammed added. She said it could take months just to secure the tunnel for investigators to safely enter.

City Councilmember Tim McOsker credited the workers for staying calm under pressure. “This is a highly technical, difficult project. And they knew exactly what to do; they knew how to secure themselves. Thank goodness for the good people that were down in the tunnel,” he said.

Mayor Karen Bass praised the outcome. “I know when we raced down here, I was so concerned that we were going to find tragedy,” she said. “Instead, what we found was victory.”

City officials say work will remain paused until the site is deemed structurally safe. Industry experts stress that while rare, partial tunnel collapses underscore the extreme engineering challenges of urban underground projects near coastlines. OSHA and local agencies are expected to take part in the probe. Local labor unions have called for increased safety reviews for all large-scale underground projects citywide.

Originally reported by Julie Watson and Christopher Weber in DJC Oregon.