The Orange County Flood Control District retained Tetra Tech to complete the preliminary and final design to relocate the existing Santa Ana River Interceptor (SARI) as part of the U.S. Army Corps of Engineers Santa Ana River Mainstem project in Southern California.

The project includes unique financing; acquisition of right-of-way from the California Department of Transportation (Caltrans); minimizing construction effects to sensitive plant and animal species; and protecting the water quality of the Santa Ana River, aquifer, and beaches.

The Orange County Sanitation District constructed the existing interceptor in the early 1970s. This project replaces 3.7 miles of 39- to 45-inch vitrified clay pipe and 42- to 45-inch reinforced concrete pipe with 3.85 miles of 54-inch gravity sewer, roughly from Green River Golf Course to the SAVI Ranch control gate structure in northern Orange County.

The SARI conveys brines and wastewater from factories, biosolids treatment facilities, and brackish water desalination plants as well as domestic waste, currently averaging approximately 12 million gallons per day of total flow. Spills could be catastrophic to the sensitive plant and animal wildlife within the Santa Ana River. In addition, the Santa Ana River flows are diverted by Orange County Water District to settling basins to recharge the aquifer in which potable water is extracted. The aquifer damage would have a significant effect on the water purveyor’s ability to supply potable water in a timely and cost-effective manner to much of northern Orange County. Furthermore, beach closures would mean loss of tourist income and negative publicity for coastal communities.

Tetra Tech’s scope of work involved completing all geotechnical studies, including a geotechnical data report, geotechnical interpretive report, and geotechnical baseline report; completing a field survey to verify topography, utility research, base mapping, and potholing; completing a preliminary design evaluating several alternatives including hydraulic capacity and pipe sizing, deep gravity, pumping, siphons, various tunnel methodologies, pipe material alternatives, bike detour alternatives, and access road design; preparing a supplemental environmental assessment; leading public relations efforts; and cost estimating.

Tetra Tech helped procure permits from the City of Anaheim, City of Yorba Linda, Caltrans, State Parks of California, U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, California Department of Fish and Game, State and Regional Water Quality Control Boards, and CalOSHA Mining and Tunneling Unit.

Tetra Tech also provided bidding support and construction phase engineering services to respond to a request for information and clarification; reviewed shop drawings; reviewed an “or equal” substitution request; completed field biological monitoring; and assisted with public relations efforts, startup and commissioning, and record drawings.

The project was vetted through a formal value engineering process. Results of the value engineering study validated the preliminary design results, including the preferred alignment, alternatives, and estimated construction costs.

The final sum of these efforts consists of two bid packages: the Yorba Linda Spur, awarded to LA Engineering for $7.2 million, and the SARI Mainline and Metering Station, awarded to W.A. Rasic Construction for $41.85 million.


The project received the 2015 Wastewater Conveyance Project of the Year award from the American Society of Civil Engineers Orange County Branch.