A Report on OCWA’s February 2020
Industry Insight Presentation
South Coast Water District
Digs in Deep
Massive, Multi-Year Tunnel Project
Is an Engineering Marvel
By Tim Hogan
It’s a renovation project few would relish: A decaying, two-mile long tunnel, hewn into a rocky oceanside cliff, with a 24" gravity-fed sewage pipeline in need of replacement, all situated beneath scores of beachside properties.
Daunting as it sounds, the task was especially foreboding, for over a million gallons of wastewater are channeled daily through this critical line, and disrupting the flow was out of the question. Nor could there be any spills, for the project was directly adjacent to protected coastal marine conservation areas.
This was the scene described by Joe McDivitt, Chief Operations Officer for South Coast Water District, when he joined OCWA for February’s Industry Insight event, to discuss the Beach Interceptor Sewer Tunnel and Pipeline Replacement Project. It was a remarkable tale, a story of near endless permits and easements, a constant balancing of the job with the need to maintain public confidence, all while carrying out a challenging feat of engineering.
Speaking before a capacity crowd, McDivitt explained that when the decision was made to upgrade, the tunnel and sewage line were over 60 years old. Built when Laguna Beach was a rural community with few homes and businesses, current conditions are decidedly different. Now there are a plethora of agencies guarding the land and coast, and hundreds of vested homeowners above the line — many of whom were unaware of the tunnel beneath their property.
Much of the original tunnel was dug by hand, but some areas were blasted, primarily through bedrock, to forge the approximately six-foot square passage. While the rock formed a solid structure, the earthen sections were shored up with treated timbers. And while the original, gravity-fed pipeline, ingeniously designed to eliminate the need for numerous lift stations along the coast, had served the needs of an ever-increasing number of people, homes, and businesses, it was showing its age and needed to be replaced.
Plans called for the new tunnel to be enlarged to about 9-feet square with a “horseshoe shape,” rounded at the top. It would also be built above the original pipe, which would be retained for emergency use but encased in concrete for protection during the construction project. A new, 24" replacement sewage pipe would be installed in the new tunnel. And the tunnel itself would be lined with steel beams and reinforced shotcrete – sprayed in concrete – to provide both structural reinforcement and a safe working environment.
It was anticipated that over 29,000 cubic yards of rock, dirt, and lumber would need to be removed from the tunnel, approximately 3,000 round trip truck loads.
To speed access both for the upgrade and for ongoing maintenance, new staging and work areas would be built and a new access shaft installed. And to the relief of all the homeowners and businesses nearby, there would be no blasting as was employed in 1954. New machinery would be brought in to bore out the tunnel, and removal of debris would be tightly controlled.
The project is estimated to take six years. When completed, the replacement would ensure reliable sewer service for another 100 years, prevent sewer spills, and provide better access for maintenance and safer work conditions.
Before it could begin, however, there were extensive community outreach meetings, held to both educate the citizens and hear their concerns. From these listening sessions, the District identified numerous areas for analysis, among them aesthetics, air quality, noise, traffic, recreation, and biological, paleontological, geological and geotechnical resources. Historical resources were also analyzed because of possible impacts on one of the tunnel access locations in the plan.
The public outreach effort paid off. It took three years, but the District was able to acquire 196 new easements from the private property owners on the bluff. And there was only one lawsuit, eventually settled in favor of the District.
The necessary permits took years to acquire as well, but due diligence and careful adherence to procedures proved invaluable. Among the many permits required, the District had to obtain California Environmental Quality Act approval, Coastal Commission Permits, California Environmental Quality Act approval, Caltrans Encroachment Permits (to construct an access tunnel beneath Coast Highway), OC Harbor and Beaches Permits, Coastal Development Permits and Conditional Use Permits from the City of Laguna Beach, and a Temporary Use Permit from the City for a house adjacent to the Staging Area to be used as a Project Office.
The Staging Area proved another sticking point. The District purchased property at 4th Avenue and Pacific Coast Highway, an old residential site. But before the dilapidated structure could be removed, and the site cleared for construction of the Tunnel Access shaft, approval from the City Heritage Committee, Planning Commission, and City Council had to be obtained, as well as a Coastal Development Permit. Eventually, all was approved, and construction of the shaft, and work on the tunnel, could begin. Click the image below to see an animated perspective on how the work was accomplished.
Construction has been steady the past three years, and completion is estimated to be done in October of 2023. So far, construction costs to date total a little over $47 million, with an estimated overall project cost of $94 million.
In conjunction with its partners, Mott MacDonald Group, Parsons Corporation, and Drill Tech Drilling and Shoring, South Coast Water District is proud to note that this project has fulfilled all its earliest expectations and been well-received by the community at large. The District is even more pleased to confirm it has never experienced a sewer spill onto the beach or ocean since the tunnel sewer line opened in 1954.
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OCWA was proud to host this very informative talk by Joe McDivitt. His presentation continued the Association’s tradition of offering exceptionally well-received Industry Insights and helped continue the great start we’ve had in 2020. This is in keeping with the Board of Director’s commitment to provide quality, timely information for the Association’s members.
For those interested, a PDF of the PowerPoint presentation is available for download by OCWA’s members only. Yet another great reason to consider becoming a member if you aren’t one already.
Next month’s Industry Insight will address one of the more critical issues facing the water industry: the “forever chemicals,” PFAS.
Presented by Jason Dadakis, Executive Director, Water Quality & Technical Resources at Orange County Water District, his talk will address PFAS in the Orange County Groundwater Basin: Occurrence, Regulation, and Impacts on Local Water Supply.
As head of the first public agency laboratory in California to achieve state certification to analyze for PFAS in drinking water, Mr. Dadakis is uniquely qualified to help guide us all to a better understanding of current PFAS research and the prospects for its removal.
Plan now to attend. But make reservations early: the last few presentations have seen capacity crowds fill the room. You won’t want to miss out!
Reservations can be made on ocwater.org.
See you March 18!