Tunnel Stabilization And Sewer Pipeline Replacement — Laguna Beach, CA

  • South Coast Water District (SCWD)
Project Value

$90 Million


Tunneling, Water And Wastewater


Engineering, Program/Construction Management (PM/CM)

The South Coast Water District operates the Beach Interceptor Sewer Tunnel located beneath the coastal bluffs in the city of Laguna Beach, California. The rehabilitation efforts of the 70-year-old sewer tunnel include the stabilization and enlargement of a 10,000-foot horseshoe-shaped tunnel from five feet wide by six feet high to eight feet wide by eight feet high horseshoe-shaped tunnel using roadheader excavation and conventional ground support. The old deteriorated ‘Techite’ and VCP pipes have been replaced with a new 24-inch C900 PVC sewer pipe. The program also includes tunnel portals and adits modifications, dozens of lateral and utility relocations, pipe slip linings, and permanent tunnel ventilation. 

Our Role In Upgrading South Coast’s Sewer System

We provided preconstruction services, including value engineering, seismic stability analyses, and risk assessment to the South Coast Water District. Additionally, we have provided bid support, design reviews, and construction management services since 2016. Construction is currently in the final of four phases. Tunnel excavation and support and the installation of a new 24-inch PVC sewer pipe were completed in mid-year 2023. The critical sewer flow switchover from the old pipe to the new pipe was completed successfully in June 2023.

Notable Services

  • Avoided and mitigated settlement-induced damage to existing buildings, structures, and utilities.
  • Performed conventionally and hand-mined complex tunneling through poor ground at portals, adits, and low-cover areas.
  • Delivered the project safely within a tight budget to the desired quality and schedule, while meeting all environmental commitments.
  • Dealt with a complex public environment surrounding the project successfully

Expected Project Completion And ACEC 2024 Merit Award Winner

The final completion of the project is expected in May 2024.

Along with our client, South Coast Water District (SCWD), we were honored to receive the ACEC 2024 Merit Award at the ACEC-California Engineering Excellence Banquet for this two-mile-long Tunnel Rehab Project in Laguna Beach, CA.

Groundbreaking Tunnel Innovation

For over 70 years, we’ve planned, designed, engineered, built, and managed complex tunnels from transit to sewers and pipelines. Many of these projects involve challenging geologic environments, from seismically active Southern California to the Chesapeake Bay’s alluvial littoral. Our unparalleled experience includes over 250 tunnels and ocean outfalls around the globe. Learn more.

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