A California City’s Groundbreaking Path to Water Self-Sufficiency

On Main Street in Santa Monica, Calif., a parking lot sits between the courthouse and a boarded-up convention center. Visitors looking for a parking spot or charging their electric vehicles would never guess that a world-class water management system churning out millions of gallons of purified water sits underneath it.

The city’s Sustainable Water Infrastructure Project (SWIP) is a state-of-the-art water recycling system that has helped bring Santa Monica 85 percent of the way to complete water self-sufficiency. Groundwater from the Santa Monica Basin is the major source of supply for the city, augmented by purchases from the Metropolitan Water District of Southern California. In 2011, the city was importing almost half its water, generating fears about what officials would do in case of an emergency.

“They were fearful of what would happen to us if an earthquake disrupted the water supply,” says Sunny Wang, the city’s water resources manager.

So the City Council asked its water resources division to investigate what it would take for Santa Monica to be water self-sufficient. A sustainable water master plan published in 2018 laid out a portfolio of projects that could bring the city to 99 percent self-sufficiency by 2023. Funding issues forced the cancellation of projects that would have made this possible, Wang says, but making it to 85 percent is a big improvement.

Santa Monica has made significant progress in a complex situation. The city has dual water stewardship responsibilities: meeting the needs of residents and limiting pollution in rainwater that streams down the hills above it into the ocean. It’s found a way to advance both of these goals through a recycling program with first-of-its kind elements that have earned national and international recognition.

From Hazard to Resource

SWIP receives three kinds of water: stormwater, urban runoff and municipal wastewater. It uses advanced purification processes to bring them to drinking water standards. It’s the first underground water treatment project to accomplish this with both stormwater and raw wastewater in the same facility.

Each day, the facility produces 1 million gallons of purified water, enough to meet the needs of more than 20 percent of the city’s population. It reaches 50 to 60 feet into the ground.

“That’s a five-story building,” Wang says. “Imagine all that just placed underneath the parking lot.”

An important piece of this subsurface infrastructure is a 1.5 million gallon stormwater harvesting tank. More than 30 billion gallons of polluted runoff enter Santa Monica Bay each year through its storm drains. The tank can’t hold all of this, but it can divert enough to make a significant dent in how much pollution reaches the ocean.

The purification process is the same for all water sources, but wastewater receives additional treatment before it enters this system. The finished product exceeds drinking water standards, but it doesn’t go straight to customers.

For now, it goes back into the aquifer. “In the near future, we’re looking to direct potable reuse,” Wang says. Regulations for this were approved in California in 2024, but no public water system in the state has yet received a direct potable reuse permit.

Public queasiness about this next step is its own challenge, one Wang says the city is slowly overcoming. “The water quality is there — it’s getting over that human hurdle.”

Finding Funds

One of the biggest challenges for a project like this, Wang says, is that the city’s water utility is a not-for-profit business. Its tier one water rate is a penny a gallon, pricing unlikely to yield the $96 million cost of the water recycling project.

SWIP began to move from concept to reality when a feasibility study was completed in 2016. The combination of city leader commitment and a well-considered plan of action opened the door to support from state and county sources.

This has included a low interest loan from the state’s water resources control board and funding from a Los Angeles County clean water program. The Metropolitan Water District also provided support, recognizing that progress toward self-sufficiency would reduce the city’s need for water that L.A. County receives from the Colorado River.

Construction began in 2020 and was completed in 2022. This outcome was only possible through collaborative effort between multiple agencies, the state, regulators and local residents, Wang says.

It’s OK to Be First

Local leadership over a long period of time has been a huge factor as well, says water scientist Mark Gold, Santa Monica’s representative on the Metropolitan Water District board. “We had the first sustainable city plan in the country way back in 1994,” he says.

Gold chaired Santa Monica’s environment and sustainability commission for 28 years. He sees SWIP in the context of a comprehensive approach to water management that goes back to the 1990s, when the city’s groundwater was so contaminated it had to import 100 percent of its water supply.

Since 2001, an urban runoff facility adjacent to the Santa Monica Pier has recycled water for landscape irrigation, offsetting the need to use drinkable water and mitigating ocean pollution. The self-sufficiency plan adopted in 2018 outlined steps to reduce demand by 20 percent through conservation.

“We have a net zero water ordinance that says new development can’t use more water than pre-existing development,” Gold says. “If it does, you have to pay an in lieu fee [one paid in place of meeting a requirement] for conservation measures in the rest of the city.”

Wang is an engineer by training. Before he came to Santa Monica, he was a consultant for an Orange County system that replenishes its groundwater supply by purifying treated wastewater from its sanitation district. It’s the world’s largest project of this type. This experience with advanced purification systems helped Wang hit the ground running when he came to the city seven years ago.

“I love working on cutting-edge projects, something that hasn’t been done before,” Wang says. “For things like this to happen, you need city leadership to have foresight, to give direction, to encourage staff to be innovative.”

A lot of municipalities don’t want to be the first to try something new, he says. “Our City Council says, ‘Hey it’s ok, we could be the first. You just have to have a Plan B.’”