There’s been a pipeline floating on top of the Miramar Reservoir in San Diego. It is one end of an 8-mile conduit that will connect the reservoir to the city’s wastewater recycling plant, now under construction. Later this week, this part of the pipeline will be under 100 feet of water.
“We are getting ready to install an approximately one mile branch pipeline that will be built above water and will be sunk in place, to allow us to distribute purified water evenly within the Miramar Reservoir,” said Elif Cetin, a civil engineer with San Diego’s Strategic Capital Projects Department.
San Diego’s planned facility to recycle wastewater is the most expensive capital project in the city’s history. Phase One alone will cost $1.5 billion. This week the construction work goes underwater. But that’s not a problem.
“We have divers,” Cetin said.
“At any given time there will be five divers. The majority of them will be installing, handling the coupling and installation process. And there will be a diver who is doing the inspections for quality control.”
In a state where water is always in short supply, purifying sewage and greywater is becoming an important way to meet the need. Phase one of San Diego’s Pure Water Program will be completed later this decade and it'll produce 30 million additional gallons a day for the city.
Richard Fernandez is a construction engineer who’s overseeing the pipeline project. He says California regulations require recycled waste water to go through a process called indirect potable reuse. That means treating the waste water, then storing it in a reservoir and treating it again before it flows through your tap.
“So rather than direct potable reuse, we’re doing indirect potable reuse, which is an added step for safety in case anything does go wrong at any one of those steps. There is some discontinuity between them so you can address that safely and be a little more conservative with the approach,” Fernandez said.
The city of San Diego isn’t the only place in the county that’s recycling waste water.
In 2022, four East County water agencies broke ground on a water purification plant to produce about a third of those agencies’ daily water supply. Oceanside has already begun supplying residents with purified recycled water. Three million gallons a day.
San Diego’s recycling plant will be by far the biggest and most productive in the region. Fernandez says the city needs its own locally controlled water source.
“Living here, the elephant in the room is there is really no water locally available,” he said. “This project provides a way for San Diego to provide safe, reliable, locally sourced drinking water, something that we really have never been able to do.”
San Diego’s Pure Water treatment system will be operational and providing seven million gallons of water a day to residents by 2026. The City says it will be at full capacity, providing nearly half the city's water needs, by 2035.
