The Clearwater Tunnel Project is a critical infrastructure initiative developed to protect local waterways and ensure the reliability of the A.K. Warren Water Resource Facility (Warren Facility) and the Los Angeles County Sanitation Districts’ (Districts) Joint Outfall System (JOS), which serves over five million people in the Los Angeles basin. When completed, this tunnel will safely transport our cleaned wastewater to the ocean directly from the Warren Facility. This tunnel is being constructed by Flatiron/Dragados (F/D) to address the following issues:
Aging infrastructure – The existing tunnels, which were built in 1937 and 1958, have never been taken out of service since they began operating. Their current condition is unknown. When complete, the Clearwater Tunnel will allow these pipes to be taken out of service and inspected.
Earthquake concerns – The existing tunnels are not built to modern earthquake standards, and they cross two known earthquake faults.
Overflow concerns – The capacity of the existing tunnels was nearly exceeded twice during major rainstorms, including the rainstorms in January 2017 and February 2024. When capacity is exceeded, partially treated or untreated wastewater might get discharged to surrounding waterways, resulting in poor water quality and health hazards.
Construction of the Clearwater Tunnel Project began in 2019 in the City of Carson and was previously projected to conclude around 2027 at Royal Palms Beach. Due to the tunnel breach that occurred on July 9, 2025, completion of tunnel construction has been delayed. Construction work is currently focused on three areas: 1 – preparation of infrastructure at Royal Palms Beach to eventually connect the new tunnel to ocean outfall pipes, 2 – tunnel repair and recovery work inside the tunnel where the breach occurred, 3 – surface and below ground monitoring work directly above the breach on Western Avenue near Weymouth Place.
On July 9, 2025, the tunnel experienced a partial breach near its top resulting in the immediate evacuation of tunnel workers and a shutdown of the project. No one was physically injured and all workers were safely removed from the tunnel. Since then, significant efforts have been made to stabilize the breach area, conduct tunnel repairs, remove ground water that is entering the tunnel, and study the breach for a root cause of the failure.
Safety inside the tunnel is our top concern. Progress inside the tunnel has been slow and difficult due to space limitations, debris and the water still inside. All work inside the tunnel since the breach has been conducted under the supervision and approval of CalOSHA inspectors. F/D is the Districts’ contractor and is responsible for tunnel workers and work conducted inside the tunnel. To date, the Districts have been advised by our third-party consultants that the tunnel’s design is safe and the design specifications used to build it are sound. The tunnel’s design specifications - as built - have been reviewed by the Districts’ third-party experts using multiple engineering evaluation methods which have validated the tunnel design as sound assuming construction specifications were used.
Construction teams have made measured progress preparing the Royal Palms Beach site to connect with the new tunnel. Construction activities are limited due to ongoing archeological work related to the discovery of cultural artifacts. All construction in this area is proceeding slowly and methodically while archeology work continues.
Work inside the tunnel to repair the breach, remove debris and water and move forward to recover the tunnel boring machine (TBM) is in discussion with F/D. The TBM remains in the tunnel approximately one mile ahead of the breach area. No workers, equipment or investigations have proceeded beyond the breach to date. Best estimates indicate it could take up to one year to reach the TBM and potentially resume tunnel construction. All construction projections are subject to change.
On July 8, 2026, an individual lawsuit was filed by a construction worker (employed by F/D) who was in the tunnel at the time of the breach. The Sanitation Districts are one of numerous defendants named in this complaint. The Districts filed a cross-complaint on September 11, 2026, against F/D to ensure that this case is defended under the terms of the Districts’ construction contract. All allegations in the plaintiff’s complaint are addressed and denied in our cross-complaint.
To read the full report click here.
During the past year, the Districts consulted with all parties involved in the construction and design of the tunnel. In September 2025, the Districts retained a third-party expert – Hatch (a professional geotechnical, structural, and tunneling engineering services firm for major global infrastructure projects) – to conduct an extensive root cause analysis of the tunnel breach failure. Based on the information available to date, this report determined the most likely cause of the failure was due to an insufficient amount of grout leading to the initial deformation of the tunnel lining and compounded by an inadequate response to fix the damage. Injection of grout around the outside of the tunnel segments is a critical function of the TBM and the construction process used to stabilize the entire tunnel and ensure its long-term integrity. Grout (cement), is used to backfill sections of the tunnel to stabilize its structure against the pressure of the earth it was constructed in, include the breach location. The Hatch Report points to an insufficient amount of grout used around the OUTSIDE of the tunnel segments to create enough stability and strength to withstand the external ground forces at this depth. Also, the report found that the interim fix installed by the contractor was inadequate and that additional measures could have been taken to prevent the breach.
As of today, the Districts and its contractors continue to work on the safest and best engineering solutions to move the project forward to completion. Both parties’ management teams are meeting regularly to accomplish this. We are working with all parties involved on every aspect of the tunnel’s safety, engineering, repair and design to reach our completion goals and put the tunnel into service as intended. The Districts’ goal remains steadfast – to build safe and sound infrastructure that will serve public’s wastewater management needs for generations to come.
For questions, please contact Michael Chee, Public Information Officer, at michaelchee@lacsd.org.
