Communities living with one of the most severe pollution problems in California could see immediate relief if San Diego leaders can get a key Tijuana River project out of the gate. 

While millions of gallons of untreated sewage enter the river on a regular basis, one road crossing, known as the Saturn Boulevard hot spot, is the source of most airborne pollution from the river. 

As the U.S. and Mexico pursue a combined $800 million in upgrades to wastewater facilities on both sides of the border, local governments are working on a smaller fix to that chokepoint that could improve conditions as soon as next year, officials said.

San Diego leaders are trying to secure about $25 million to repair the road crossing at Saturn Boulevard, where sewage-tainted water is forced through outdated culverts that spew hydrogen sulfide gas and other toxins throughout south San Diego.

Fixing the hot spot can “mitigate the turbulence in that area, which will mitigate the emissions that basically rocket aerosols into the air,” said San Diego County Supervisor Paloma Aguirre, who has spearheaded efforts to clean up the river.

But they’re still trying to nail down a funding source for the project. 

Sewage pollution from the cross-border river has plagued Imperial Beach, Coronado and other parts of southern San Diego for decades. The threat rose as the Tijuana population grew and wastewater plants on both sides of the border failed, spilling hundreds of millions of gallons of raw sewage into the ocean in recent years.

San Diegans have long known that raw sewage in the ocean is a hazard to swimmers and surfers, and local beaches have been closed for years. Then in 2024, researchers with UC San Diego Scripps Institution of Oceanography discovered that the pollution wasn’t just fouling the water. It was also contaminating the air. 

The river emits airborne chemicals including hydrogen sulfide gas, which cause respiratory problems and other ailments among people in neighboring communities. 

Residents experience asthma, stomach problems, skin rashes and headaches, even without going in the water. Parents are wary about letting children play outside. Local schools enforce “rainy day schedules” to keep students inside when air quality worsens.

Researchers traced the air pollution to the Saturn Boulevard hot spot. It’s a culvert set along a rural road near the Tijuana River. The structure, which includes several large concrete pipes, was built decades ago to divert flood waters from neighboring farm fields. When it rains, water trickles across the road and gushes through the pipes, creating mounds of foam and spraying contaminants into the air.

San Diego County officials are trying to secure money to fix that. They estimate it will cost about $25 million to re-engineer the site in order to control the flow of floodwater and prevent it from releasing toxic gas and airborne particles.

There are several parallel tracks to funding the project, but none of them is certain.

One is a pot of money in Proposition 4, the $10 billion climate bond measure that California voters approved in 2024. It includes about $50 million for border projects on the Tijuana River in San Diego and New River in Imperial County. 

Although it passed two years ago, the funds haven’t been released because of administrative procedures that slowed their disbursement. This year state Sen. David Alvarez, a San Diego Democrat, introduced legislation to waive some red tape and speed up funding through the bond measure. 

With the money now available, the State Water Resources Board will accept grant applications for the funds this summer between June and August, and then score and award them by early next year, said Jennifer Toney, a senior engineer with the State Water Resources Control Board. Local governments and nonprofits working on those rivers are eligible to apply.

The board could award up to $20 million for construction such as the Saturn Boulevard project, Conty said. But it faces competition from other possible Tijuana River efforts such as sediment removal, trash capture and others, as well as proposed projects on the New River, Toney said.

On a separate track, state lawmakers have submitted a request in this year’s state budget for $23 million to cover most of the Saturn Boulevard construction. If that’s approved it could free bond money for other border river projects.

A third possible funding source is a proposed half-cent county sales tax, entitled  “Protect San Diego County Health and Safety Act,”  which goes to voters in November. It could generate $360 million per year, with about $80 million of that earmarked for Tijuana River improvements. 

The measure calls for up to 22.5% of tax revenue to be spent on environmental mitigation to address “the toxic sewage crisis in the Tijuana Valley.” But it doesn’t spell out specific projects such as the Saturn Boulevard site, KPBS reported.

In the meantime, an even quicker temporary solution expected to cost $2.5 million could be in place by this time next year. The temporary fix will extend the existing pipes and transfer the flowing water downstream through an enclosed system, County Public Works Director Marisa Barrie stated in an email to CalMatters. That will reduce the churn that causes pollutants to become aerosolized.

“The team evaluated infrastructure mitigation options at the Saturn Boulevard hot spot and agreed to move forward with a short-term solution that will offer tangible immediate benefits,” Barrie stated.

Design, environmental analysis, and permitting for that project is in the works now, Barrie said. It should take about three months to construct, and county officials hope to complete it by March, 2027, before nesting season for birds in the area. 

Aguirre cautioned that reengineering the culvert won’t clean up the river, but will reduce its impact on neighboring communities. “That’s not the permanent solution to the entire crisis. This is something that’s within our power to tackle, working with the state, city and county of San Diego, that we know based on empirical evidence will bring some relief to residents of affected areas.”