Work on a Los Angeles County sanitation tunnel has been halted as investigators look into what caused it to collapse Wednesday evening, leaving 31 workers scrambling to make their way to safety.
Los Angeles County Supervisor Janice Hahn, who is also on a county sanitation district board, said in a statement that the district will be looking into what caused the tunnel collapse.
“We are blessed that all of those men made it out and made it home to their families,” she said. “Most people in the Harbor Area communities didn’t even realize that this tunnel was being bored beneath them, but these men go to work every night to build this critical infrastructure project for our region. I am so grateful that they are home safe tonight.”
The only entry point to the tunnel is near the 1700 block of South Figueroa Street in Wilmington, where more than 100 L.A. Fire Department personnel were dispatched after reports of the accident, including search and rescue teams specially trained and equipped to handle confined-space tunnel rescues.
All of the workers were able to safely make it out of the tunnel, which is six miles long and 400 feet underground.
“We are all blessed today in Los Angeles, no one injured, everyone safe,” said L.A. Mayor Karen Bass, who met with the rescued workers. “I am feeling very good that this is a great outcome to what started as a very scary evening.”
The workers were in an 18-foot-diameter tunnel more than five miles from the Wilmington access point when the partial collapse occurred, said interim Fire Chief Ronnie Villanueva at a news conference late Wednesday.
There were 27 men inside the tunnel at the time of the collapse, according to Robert Ferrante, chief engineer for the L.A. County Sanitation Districts. Four others then entered in an attempt to assist their fellow workers.
The debris did not completely fill the tunnel, and the men were able to climb back through the area where the collapse took place.
“Any time you have a collapse in a tunnel behind you, there is only one way out. … So they had to come back and make their way through the damaged section of the tunnel,” Ferrante said. “It was very scary. We are very fortunate no one was hurt.”
Bass said she had an opportunity to speak with the workers and ensure they were able to reach their family members, several of whom had waited anxiously at the scene.
FlatironDragados, the construction firm running the project, thanked first responders in a statement provided to The Times. The statement touted the professionalism of the workers and confirmed that work has been suspended while the firm investigates the incident.
The accident took place in the Clearwater Project, which is designed to carry treated, clean wastewater from the Joint Water Pollution Control Plant to the ocean.
Prior to the accident, the tunnel was expected to reach Royal Palms Beach by the end of the year, at which point it would be seven miles long. The plant is the largest wastewater treatment plant owned and operated by the L.A. County Sanitation Districts.
This is the first major incident that has taken place since construction on the project began in late 2019. Work on the tunnel itself started in 2021.
But that work is paused for the foreseeable future, Ferrante said on Wednesday night. The contractor will need to go in and assess the condition of the tunnel leading up to the area that collapsed, ascertain what went wrong and figure out how to fix it.
“There’s no telling how long that will take,” he said. “It’ll take as long as it needs to make sure that the tunnel is safe.”
In a series of videos about the Clearwater Tunnel Project posted to Youtube, several Los Angeles County Sanitation Districts employees outlined the operation the tunnel boring machine used to dig the seven-mile tunnel from the Joint Water Pollution Control Plant in Carson to Royal Palms Beach in San Pedro.
The machine, nicknamed Rachel after environmentalist Rachel Carson, was lowered into the ground through a vertical shaft to a depth of 135 feet in 2020. Crews then began digging a winding, 18-foot-wide path under roads and a golf course toward the beach, filling in tunnel walls as the machine moved forward.
The boring machine has thousands of sensors and communicates data in real time. Above ground, workers can deploy sensors to measure minute changes in surface elevation and monitor stability. It was unclear whether such monitoring was happening in the area where the collapse occurred.
The tunnel miners typically work three eight-hour shifts, five days a week, for continuous 24-hour tunneling. Above ground, tunnel miners mark their names on a board before they begin their shifts so that in emergencies rescuers will know exactly who is underground.
Each miner is required to wear a safety vest, a hard hat, a hydrogen sulfide monitor, a self-rescue kit containing an air-purifying oxygen mask and rubber boots while working.
They descend the vertical shaft in an elevator then make their way through the tunnel until they reach the tunnel boring machine. The tunnel has ventilation shafts to supply breathable air to workers and fiber optic cables to transmit data to contractors and inspectors.
The purpose of the Clearwater Project is to build a more robust tunnel so that treated wastewater can be safely pumped out to the ocean from the county’s biggest treatment plant.
The existing tunnels can’t be taken out of service, were not built to today’s seismic standards, and are not large enough to handle high volume during heavy storms. A 2017 storm nearly flooded the system, and the damage from such an event could be catastrophic.
If the existing tunnels were to fail, the Joint Water Pollution Control Plant would either discharge raw sewage into nearby Machado Lake or into the Los Angeles Harbor, with environmental impacts that could last months or years, county officials said.
Hahn, L.A. City Councilmember Tim McOsker and Congressmember Nanette Barragán also came to the site of the rescue operation late Wednesday.
Hahn said that it was a traumatic incident for the men, who emerged from the shaft “alive and happy” but also “all shaken up.”