2025 West Best Projects
Best Water/Environment: Carlsbad Desalination Plant Intake and Discharge Facility
Carlsbad Desalination Plant Intake and Discharge Facility
Calif.
BEST PROJECT
Submitted by HDR
Owner Channelside Water Resources
Lead Design Firm HDR
General Contractor Kiewit Shea Joint Venture
When the largest seawater desalination facility in the U.S. officially opened in 2015, it initially relied on cooling water drawn through the Encina Power Station. Once the power station stopped operations in 2018, stakeholders had to create a temporary intake and discharge system while planning a permanent solution. This $200-million effort replaces the temporary structure with a technologically advanced, environmentally sensitive seawater intake and discharge facility.
The project, part of the multi-decade strategy to diversify the county’s water supply and minimize drought vulnerability, will allow the desalination plant to continue delivering 50 million gallons per day of water to San Diego County Water Authority.
To implement the system, the team used complex computational fluid dynamic modeling and a collaborative, multiphased design-build approach. Construction proceeded while the team maintained active plant operations. This project also features the country’s first 1-millimeter screens to filter seawater—a total of 11 screens help protect marine life and reduce intake water velocity.
Photo courtesy HDR
Due to supply chain issues and the project’s short schedule, the team procured equipment before final design when possible. Several items, including the screens, pumps and electrical components took more than a year to obtain, while other items took months.
As for the new intake itself, it’s designed to weather tidal fluctuations, sea level rise, tsunamis and earthquakes, all while resting on challenging, highly liquefiable soils. Without abutments, the addition of more piles and a cast-in-place end span will help the facility overcome the large longitudinal displacement during earthquakes.
Photo courtesy HDR
For more than 50 years, power plant operators regularly maintained the Agua Hedionda Lagoon and dredged an opening to the ocean to sustain a source of seawater to cool the power plant’s generators. The 388-acre lagoon is a man-made, shallow coastal embayment. Now that Channelside has taken over dredging responsibility at Agua Hedionda Lagoon from NRG Energy, the intake system project will better protect the critical wildlife, the environment and the plant. It includes a 19-ft-deep mudline, with 14 ft of artificial fill and high groundwater, influenced by seawater and tides. With only a few borings spaced hundreds of feet apart, the team verified all borings struck bedrock without going too deep, which would add cost.
Photo courtesy HDR
Completed within budget and on schedule in December 2024, the new intake and discharge facility’s dual-flow screens improve sustainability, keep the lagoon productive and comply with the California Ocean Plan Amendment. To implement the system, the team used complex computational fluid dynamic modeling and a collaborative, multiphased design-build approach while maintaining plant operations throughout construction.
