The Los Angeles Clearwater Collapse. Insights On The Causes and Technical Response

On the evening of July 9, 2025, a structural failure occurred deep beneath Wilmington, Los Angeles, when a section of the Clearwater Tunnel collapsed. The project is a major component of a $700 million wastewater infrastructure upgrade. At the time of the incident, 27 workers were inside the tunnel, positioned nearly 400 feet underground and almost six miles from the sole entry shaft. Four more workers entered the site after the collapse to assist in emergency efforts, bringing the total to 31 individuals at risk.

Emergency response was immediate. More than 100 Los Angeles Fire Department personnel, including specialized Urban Search and Rescue teams, were dispatched to the scene. All trapped workers were safely extracted within a short time frame. No injuries were reported. Workers escaped by climbing over a 12 to 15-foot pile of displaced soil and navigating back toward the tunnel boring machine. This machine then transported them along the tunnel to the surface shaft where they were lifted out by crane.

The Clearwater Tunnel is designed to replace two aging outfall lines built in 1937 and 1958. It extends approximately seven miles in length and lies at a depth of 400 feet. The purpose of the tunnel is to transport treated wastewater from the Joint Water Pollution Control Plant to the Pacific Ocean at Royal Palms Beach.

Construction began in 2021 with the deployment of a tunnel boring machine (TBM) named Rachel. This machine was outfitted with modern instrumentation for real-time geotechnical monitoring. By the time of the incident, the TBM had advanced more than five miles along the tunnel alignment.

The collapse appears to have been caused by a condition known as “squeezing ground.” This occurs when geostatic pressure exerts stress on the excavation boundary, causing inward deformation. The affected tunnel segment had not yet received its permanent concrete lining, which left it more susceptible to deformation and soil intrusion. As the surrounding ground moved into the open space, a significant volume of material broke through and reduced the tunnel’s navigable diameter to only three feet in some sections.

In the aftermath of the collapse, all activities associated with the Clearwater Project were halted. Cal/OSHA launched a full investigation to identify the root cause and assess regulatory compliance. The contractor, also initiated an internal review to evaluate tunnel integrity, project protocols, and monitoring system performance.

Despite the failure, officials emphasized that emergency safety protocols functioned effectively. All personnel were equipped with self-rescue kits, gas monitors, and emergency lighting. Above-ground systems used fiber optics and geotechnical sensors to track movement within the tunnel. It is still unclear whether these systems detected precursory signs of failure.

Reports described the crew’s response as well-coordinated and in accordance with emergency protocols. Workers followed established procedures for emergency egress and made use of the TBM transport system to return to the surface. Their training and the rapid coordination of rescue personnel were instrumental in preventing injury or loss of life.