Gaps in the compacted filler grout, a cement material, have been identified as the primary cause of a significant tunnel breach during the Clearwater Tunnel Project, which caused a temporary entrapment of 31 workers on July 9, 2025. This finding emerged from a detailed report released on November 13, 2025, which outlined flaws in the infrastructure’s preparation, leading to an indefinite halt in the ambitious waste management undertaking.
The Clearwater Tunnel Project, which commenced in 2019, aimed to replace inadequately sized wastewater pipes with larger, more efficient conduits running approximately five miles from Carson to San Pedro. The tunnel breach occurred at the 5-mile mark beneath Western Avenue, where it trapped workers who ultimately managed to free themselves and walk to safety. The incident has halted construction efforts on the project, which boasts an overall budget exceeding 0 million.
The independent analysis, crafted by engineering consultant Hatch, spanned over 700 pages and detailed various factors contributing to the breach. The report indicates that insufficient cement was injected to secure the tunnel’s steel lining, creating vulnerabilities. This critical oversight may have allowed water and debris to infiltrate, compromising the structural integrity of the tunnel.
Following the breach, investigations revealed warning signs that indicated deformation and stress at the site. The report conveyed that more proactive measures should have been employed to fortify the tunnel. As officials navigate this setback, they are now prioritizing safety and recovery efforts over timelines for resuming work.
Currently, the project remains on hold as investigators work to clear debris from the site. High-tech drone technology is being utilized to assess conditions below ground, including the status of the electrically powered tunnel boring machine trapped beneath the breach. Experts estimate it to be approximately 394 feet below Western Avenue, near Weymouth Avenue.
While the project was close to completion, with the final destination being White Point/Royal Palms Beach in San Pedro, officials stated that they have no projections for when construction can resume. In light of the incident, a claim has been filed against the contractor, Flatiron Dragados, reflecting the complicated legal implications that often arise in such large-scale public works.
As the investigation continues, the Los Angeles County Sanitation Districts are taking measures to ensure that any further construction is conducted with meticulous attention to safety and adherence to engineering standards. The findings from the Hatch Report have underscored the project’s vulnerabilities and highlighted the importance of rigorous oversight in construction practices. For now, stakeholders aim to navigate this crisis while planning for the future of the Clearwater Tunnel Project. The complete report has been made available on the Sanitation Districts’ official website for public access.