Design and Construction Report staff writer
Thirty-one construction workers escaped without serious injury last Wednesday evening (July 9) after a partial collapse trapped them deep underground, inside the Los Angeles Effluent Outfall Tunnel, a $700 million wastewater infrastructure project.
The workers were 400 feet (121 meters) underground and as much as 6 miles (9.6 kilometers) away from the only exit, said Michael Chee, spokesperson for the Los Angeles County Sanitation Districts, which is in charge of the nearly $700 million project. The workers were about 400 feet (121 metres) underground.
“Any time you tunnel underground you encounter different conditions in different locations Robert Ferrante, general manager, Los Angeles County Sanitation Districts, told reporters at the rescue site. “There was a location that squeezed the tunnel forcing it to partially collapse.
“We’ll have to go back and look and see what we can do to make that repair and not only repair it but make it stronger.”
The tunnel is being constructed almost entirely underneath public right-of-way. The structure is 18 feet (5.5 metres) wide and will be 7 miles (11.3 kilometres) long to carry treated wastewater from across Los Angeles County to the Pacific Ocean.
Firefighters said workers had to climb over 12 to 15 feet (3.6 metres to 4.5 metres) of fallen dirt and debris to reach the tunnel boring machine and then were transported by vehicle back to the opening. Some people had to be pulled out.
Workers were trapped behind a 12-to-15-foot pile of dirt and debris that blocked the passage and climbed over the rubble to reach the tunnel boring machine. Colleagues then ferried them more than five miles in a tunnel transport vehicle to the safety of the access portal.
The Los Angeles Fire Department responded at 7:58 p.m. with more 100 firefighters, including Urban Search and Rescue teams trained in confined space operations. Specialized equipment, paramedics, search dogs, and drones were deployed for the complex rescue.
All 31 workers were examined onsite by paramedics and released with no major injuries. Cal/OSHA has been notified and will investigate the incident.
With early reports of a tunnel collapse behind as many as 15 workers at least five miles into the 18-foot-diameter bore, Los Angeles Fire Department responders prepared for an extended rescue operation with complex logistics as additional LAFD resources, including search and rescue canines, unmanned aerial systems (drones), hazardous materials specialists and nearly two dozen paramedic ambulance teams stood at the ready to address the unique rescue and medical needs typical of such a crisis.
Following an on-scene examination by LAFD Paramedics, they were all released at the scene.
No other injuries were reported. Cal/OSHA was notified of the workplace emergency.
