New, state-funded brackish desalination plant strengthens Antioch’s water security

ANTIOCH, CA – The State Water Resources Control Board joined the city of Antioch, the Department of Water Resources (DWR), Contra Costa Water District, the city of Brentwood and elected officials today to mark the grand opening of the Antioch Brackish Water Desalination Plant. The new facility can produce up to 6 million gallons of drinking water per day and enables the city to use and treat raw water from the San Joaquin River year-round to improve the reliability of Antioch’s water supplies.

The plant produces drinking water through the removal of salt from brackish river water. The project involved the construction of a microfiltration/ultrafiltration system for pre-treatment, and a two-stage reverse osmosis system. Depending on hydrologic conditions, the plant can account for up to half of all water generated in the city during certain months of the year and about 30% on an annual basis.

“As exemplified here in Antioch, to meet the challenges of a hotter, drier future, we must find ways to better use the water already available to us,” said State Water Board Chair E. Joaquin Esquivel. “Antioch joins dozens of other water systems who are leading the state in exploring the potential of brackish desalination to build resilience to extreme weather. We applaud the city’s innovation, and we are proud to leverage our funding to make projects like this one affordable as cities diversify their water supplies.”

The State Water Board supported the $116 million plant through a $60 million low-interest loan from the Drinking Water State Revolving Fund, a state and federal program that provides low-cost financing for a wide variety of water quality projects. The project also received a $10 million grant from the Department of Water Resources through its Water Desalination Grant Program, which is funded through Proposition 1.

The city of Antioch relies on the San Joaquin River and purchases from the Contra Costa Water District for its water deliveries to over 112,000 residents. The river’s salinity has steadily increased over the years, forcing the city to purchase more water from the district at a higher cost. The new facility can treat brackish river water at an energy cost less than half that of treating seawater.

“It was very satisfying for Antioch to work in partnership with State Water Resources Control Board and DWR to produce and finally deliver this important project,” said Ron Bernal, mayor of Antioch. “This is a fundamental component of Antioch’s health and safety plan for meeting demand during severe droughts. It will be critical for our sustainability in the future as climate change continues to make the Delta saltier.”

Desalination is an important component of Governor Newsom’s Water Supply Strategy to address an anticipated 10% reduction in water supply by 2040, which includes increasing conservation and expanding storage, recycling, and stormwater capture projects. In 2024, the State Water Board and DWR released complementary reports to facilitate desalination projects that produce water for drinking, irrigation, or other needs by removing salt from brackish groundwater. The new Antioch facility is eighth brackish desalination plant in California out of the 14 planned for the state by 2040.

“The Department of Water Resources is proud to support Delta communities in their efforts to adapt to climate change,” said DWR Director Karla Nemeth. “It’s this type of state-local partnership that enables innovative, new technologies to secure water supply over time for communities like Antioch as rising sea levels bring water quality challenges right to their doorstep.  We have to move with a sense of urgency, and this project ensures Antioch will have enough water during the next drought, which is typically right around the corner.”

The State Water Board’s mission is to preserve, enhance and restore the quality of California’s water resources and drinking water for the protection of the environment, public health, and all beneficial uses, and to ensure proper resource allocation and efficient use for the benefit of present and future generations.