The City of Antioch has completed a brackish water desalination facility to provide a drought-resilient drinking water source for more than 112,000 residents. The plant sits at the city’s existing water treatment site. It is the first desalination facility in the Sacramento–San Joaquin River Delta and the second in the Bay Area.
The new plant can treat up to 6 million gallons of brackish Delta water per day. Treatment includes reverse osmosis, membrane filtration, and ultraviolet disinfection. Once fully operational, the facility will meet up to 40% of the city’s demand. This reduces reliance on water purchases from the Contra Costa Water District. Antioch currently uses 11 million gallons per day in winter and up to 23 million gallons in summer.
Key components include a new river intake pump station with fish screens, a 3,000-foot raw water pipeline, and a 4.3-mile brine disposal pipeline to the Delta Diablo Wastewater Treatment Plant. The design reuses existing infrastructure to lower costs and reduce construction impacts.
Funding came from multiple sources. The project received $10 million in Proposition 1 desalination grants from the California Department of Water Resources. It also secured a $60 million low-interest loan from the California State Water Resources Control Board’s Drinking Water State Revolving Fund. Additional support came from local water enterprise funds.
Planning documents initially estimated the cost at $110 million. City officials now place the total investment at about $160 million.
City leaders said the facility will improve water supply reliability and protect against salinity intrusion made worse by drought. The system also provides operational flexibility under changing Delta conditions. The city expects the plant to be fully integrated into its supply network by the end of 2025.