Strengthening water security for 600,000 people in Southern California

How can we strengthen water security while putting communities first?  

The water supply of Orange County in Southern California, home to three million people and a thriving business community, has long faced challenges related to water security, groundwater contamination, drought and flooding. 

The county has relied to varying degrees on importation of water from the State Water Project and the Colorado River, resulting in higher and fluctuating water costs for residents, businesses, and public institutions.  

To strengthen water security and help address the effects of climate change, IRWD has undertaken the landmark Syphon Reservoir Improvement Project, one of Southern California’s most significant water infrastructure upgrades.  

At the heart of the project is a commitment to creating lasting value for local communities. By expanding the reservoir’s storage capacity tenfold, the project will help ensure a more reliable water supply. For the communities served by IRWD, this means greater day-to-day security, reduced dependence on imported water and more stable long-term costs.

Enhancing water resilience  

The project is transforming the reservoir into a future-ready asset that enhances water resilience while maintaining a strong focus on the people and communities it serves. 

From the earliest project stages, close collaboration with IRWD and other stakeholders has ensured that both the process and the outcome reflect community needs and expectations.  

The project team carries out detailed constructability reviews during pre-construction to identify potential issues early and to avoid delays and disruptions later. A transparent and efficient contractor procurement process further supports successful project delivery. 

How to minimise impacts on local communities 

A key priority throughout the project is minimising impacts on local communities and the surrounding environment. COWI works hand in hand with IRWD’s environmental monitoring and public outreach teams to protect sensitive natural areas and maintain transparent communication with residents.  

This involves proactive engagement, careful planning of construction activities and a continued focus on health, safety and environmental stewardship. In this way, the project delivers essential infrastructure while respecting the people and places it touches along the way. 

Delivering value for IRWD and its customers  

As construction progresses, COWI oversees contract administration, cost control and scheduling to ensure the project delivers value for IRWD and its customers. Resident engineers work closely with designers and contractors to support effective coordination and informed decision-making throughout the project.  

At the same time, rigorous quality assurance and risk management processes help ensure that every element of construction meets both regulatory requirements and long-term performance expectations. 

Improving everyday life for people 

The Syphon Reservoir expansion builds on IRWD’s long-standing leadership in water reuse, including its pioneering introduction of the “purple pipe” designation for recycled water. By enabling more water to be captured, stored and reused for irrigation and other non-potable purposes, the project supports a more sustainable and circular approach to water management, reducing pressure on potable water supplies while helping communities adapt to increasingly uncertain climate conditions. 

For COWI, the project reflects a broader commitment to building strong, trust-based relationships with clients and communities alike. Through close collaboration, transparency and a shared focus on long-term outcomes, the team supports IRWD in delivering infrastructure that not only meets technical requirements but also improves everyday life for the people who depend on it. 

The project will benefit more than 600,000 people across central Orange County communities. It also demonstrates how using the right water for the right purpose can significantly reduce pressure on drinking water supplies while contributing to a more resilient water system. 

What is the Syphon Reservoir Improvement Project in Irvine, California?

• The Syphon Reservoir Improvement Project will strengthen water security for 600,000+ people in Orange County, California.
• The reservoir’s recycled water storage capacity will increase tenfold to 6.17 million m³, enabling IRWD to store 100% of its recycled water production.
• The project includes a new dam, spillway, water treatment plant, and intake/outlet infrastructure.
• The project reduces demand for drinking water and dependence on imported water supplies.
• The reservoir upgrade enhances climate resilience, drought preparedness, flood management, and local firefighting capabilities, creating a more reliable regional water system in Southern California.
• COWI and GFT serve as project partners, delivering construction management, quality assurance, risk management, cost control, and engineering oversight during the 2026-2031 construction period.
• The project demonstrates how recycled water infrastructure can deliver sustainable, cost-effective, and resilient water management.