Tunnel Project Background

The History

For 64 years, a two-mile tunnel beneath the bluff in South Laguna Beach has carried up to one million gallons of wastewater per day to a local treatment facility. When built in 1954, the tunnel was an engineering marvel. Even today, the system is innovative because it relies solely on gravity flow, which eliminates costly and unsightly infrastructure, including unnecessary lift stations and several thousand feet of sewer lines. The system has maintained a minimal carbon footprint since its first day of operation, and it remains a vital piece of regional infrastructure.

The Challenge

The 64-year-old tunnel is in dire need of repair. It is undersized, deteriorating, and can pose a risk of injury to workers and the environment. The images below show the degraded wood-beam structures currently in place. To avoid potential catastrophe, the tunnel must be stabilized and the pipeline must be replaced.

The 100-Year Solution



South Coast Water District's Tunnel Stabilization & Sewer Pipeline Replacement Project is a comprehensive solution that will ensure safe and reliable service for the next 100 years. The project has two key components:

  • Tunnel Stabilization: The District will enlarge the size of the tunnel from an average of 5 to 7 feet. This will ensure safer working conditions and greater access for future pipeline maintenance and repair. Permanent shotcrete lining and steel supports will be installed at several locations, replacing rotten timber supports and removing loose rock.
  • Pipeline Replacement: The District will install a new 24-inch pipeline throughout the tunnel. The current 24-inch pipeline will be encased in concrete and retained for redundancy and emergency use.

The cost to repair the tunnel is estimated at approximately $90 million and will be funded through low-interest state loans, grants, and the District’s general fund.