At CWEA’s AC26 South Coast Water District (SCWD), Collection System Supervisor Daniel B. Guerra and Collection System Operator II Raymond Zarate will lead a Collection System Frontline session sharing their insights on the District’s award-winning Capital Project: Tunnel Stabilization & Sewer Pipeline Replacement Project (Tunnel Project). The 15-year effort modernized a 1954 tunnel and gravity sewer system and was delivered with an experienced team: Mott MacDonald as designer, Parsons as construction manager, and Drill Tech Drilling & Shoring as the prime tunneling contractor.
The Tunnel Project, mainly serving South Laguna Beach and northern Dana Point, was completed in 2024 and is one of the District’s most vital infrastructure assets. In this presentation, Guerra and Zarate will offer a comprehensive overview of the Tunnel Project with a special focus on how operations and maintenance were prioritized during design and construction.
“The Collection System team played a hands-on role during construction, helping ensure the system would be functional, serviceable, and safe to maintain for decades to come,” Guerra said.
In 2008, SCWD began planning to restore the two-mile tunnel. The 65-year-old structure, once considered an engineering marvel, had fallen into serious disrepair. The tunnel was too small for safe access, deteriorating, posed risks to workers, and was susceptible to failure, potentially impacting the environment. The original tunnel’s sewer pipeline, which resided inside the tunnel, was constructed using Vitrified Clay Pipe (VCP), a durable, corrosion-resistant pipe commonly used for gravity sanitary and storm sewer systems during that period.
“The sewer pipeline was upgraded to Techite™ in the 1970’s, but by the early 2000’s the sewer pipeline, along with the timber-lined tunnel, was also failing, and both needed to be rehabilitated,” Guerra said.
By 2010, SCWD had completed the EIR and began working on securing funding and Coastal Commission permitting; the latter was granted in 2016. SCWD also completed a Value Engineering study in February 2016, when the SCWD Board selected the larger horseshoe design, which provided a significant safety upgrade, along with more robust structural protection of the pipeline carrying an average of one million gallons of raw sewage per day. This allowed SCWD to begin construction on the project in 2017.
The new pipe used in the tunnel rehab is C900, a specific type of PVC (polyvinyl chloride) pipe that meets the American Water Works Association (AWWA) standard for municipal water transmission and distribution.
The eight-foot horseshoe-shaped tunnel was completed in four phases and cost $100 million, funded with the help of the State Revolving Loan Fund.
“During the project duration, the existing sewer line was, and had to remain, operational so it was important to protect the existing live sewer while building the new one,” Guerra said.
As with any large project, Guerra said that there were a few obstacles along the way. One included a partial collapse of the existing tunnel that required rerouting a section and bringing outside experts to help amend the plan. The change included adding a small lift station and upgrading the existing 11 adits (horizontal or nearly horizontal tunnels used for specific purposes, such as connecting pipes or providing access for maintenance) along the tunnel and replacing 80 laterals.
The AC26 session will begin with an introduction to SCWD’s service area, including information on the sewer infrastructure spanning 140 miles of pipes, 14 lift stations, and three miles of force mains, accessed via 3,800 maintenance holes. These force mains channel wastewater to either the Coastal Treatment Plant in Laguna Niguel or the J.B. Latham Treatment Plant in Dana Point. The South Orange County Wastewater (SOCWA) manages both facilities. They will also give information on the tunnel’s purpose, history, and the need for stabilization.
Guerra will detail the main tunnel assets, including pipe materials, structures, and access features. He’ll share how his team’s input influenced design and construction improvements that directly support maintenance efficiency. Zarate will highlight the development of a new maintenance schedule, inspection routines, and monitoring methods tailored to the upgraded system. Additional topics will include entry procedures — covering safety protocols, equipment needs, and authorization processes — and cleaning procedures, such as hydro-jetting and debris removal.
“This session will demonstrate the value of integrating operator experience into project design and construction, and how doing so can lead to smarter, more maintainable infrastructure from day one,” Guerra said.
Guerra has worked for SCWD for three years as the Collection System Supervisor. He is an experienced wastewater professional with 14 years of wastewater experience and seven years of underground utility work.
Zarate began working at SCWD two years ago as a Collection System Operator II. He also has 20 years of experience in Wastewater Collection at other wastewater agencies.
This is one of many frontline sessions at AC26 where operators and practitioners share real project lessons — from design to construction to long-term maintenance.
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