19 Sep Antioch Marks Activation of Desalination Plant That Will Produce 6 Million Gallons of Drinking Water per Day

Route in orange marking the path of a pipeline transporting brackish water from the  San Lorenzo River to a desalination plant in Antioch. A blue line shows the path of the brine that will be moved to the Delta Diablo Wastewater Treatment facility before being released back into the river and Delta. (City of Antioch via Bay City News)

By Thomas Hughes
Bay City News

A long-anticipated desalination plant that will convert the mixture of salt- and freshwater known as brackish water from the San Joaquin River mouth into drinking water for the city of Antioch launched operations this week.

The roughly $116 million Brackish Water Desalination Plant will ultimately produce as much as 6 million gallons a day of potable water, enough to provide up to 40% of the drinking water for the city of about 112,000 people, according to the city and the California Department of Water Resources.

The plant is second in the Bay Area and the first in the Sacramento-San Joaquin Delta. It is one of 14 planned or already operating around the state as part of a strategy launched in 2022 by the state to create more water security in the face of climate change, drought, and changing conditions in the Delta.

The Antioch plant was pitched as both a way to increase what the state calls regional water “resilience” and address rising salinity levels in the San Joaquin River.

The plant was conceived of more than a decade ago and planning began in earnest in 2016 with the application for a state loan to get the process started, according to city documents. The city of Antioch contributed $17 million to the project, which consisted of a new intake pump in the San Joaquin River, the facility, and 4.3 miles of new pipeline to take the brine left over from the process to the Delta Diablo Wastewater Treatment Plant before being discharged back into the Delta.

The desalination facility was constructed at the site of the existing water treatment plant at 401 Putnam St. City leaders and state and regional water officials held a ribbon cutting at the plant Monday.

Antioch Mayor Ron Bernal said the desalination plant was “a transformational investment that not only provides a critical water supply to meet Antioch’s health and safety needs during severe drought, but improves drought supplies for our neighboring members of [Contra Costa Water District] and protects Antioch’s water rights and Delta diversions for decades to come.”

The city said salinity levels would rise near the brine discharge point west of the intake pumps but would be within a range that was safe for local species.

Ian Wren, senior staff scientist for the environmental nonprofit organization San Francisco Baykeeper, said ongoing monitoring of salinity levels, particularly downstream, was one of the organization’s biggest concerns with the plant.

Wren said the organization understood the need for the city to create sustainable water supplies but urged other measures like conservation and exhausting all methods of water recycling before turning to desalination, warning it would not be a “panacea” for the region’s water problems. He said managers of the water coming from its source in the Sierra Nevada mountain range needed to decrease diversions to farmland that were contributing to the rising salinity levels in the Delta.

“The Bay needs more freshwater, not less. And that means that state agencies need to be making smarter long-term water policy decisions that will reduce diversions and keep more freshwater flowing into the Bay,” Wren said in a written statement.

He said San Francisco Baykeeper would continue to monitor the impacts on species from the brine discharge created by the desalination process.

“The success of this first-in-the-Delta desalination project will be measured not just by its water production, but by its long-term environmental stewardship of our already stressed Bay-Delta ecosystem,” Wren said.

Desalination of brackish water uses half the energy as desalination of seawater and produces about a quarter of the waste, according to the city.

Once fully running, the plant will produce about 3,000 acre-feet of water per year. The state has set a goal of producing 28,000 acre-feet of desalinated brackish water annually by 2030 and 84,000 acre-feet per year by 2040, according to the Department of Water Resources.

Karla Nemeth, the department’s director, said the desalination plant was exactly the type of project that would lead to sustainable water solutions to guard against climate change.

“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,” Nemeth said. “We have to move with a sense of urgency and this project ensures Antioch will have enough water during the next drought which is right around the corner.”

The project was funded in part by a $10 million grant from the state’s Proposition 1, a $7.5 billion bond measure approved by voters in 2014 to pay for a range of water infrastructure and conservation projects.

The Department of Water Resources also provided $60 million in low interest loans to the city to construct the plant.

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