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Earlier this week, a huge batch of sewage gushed into the San Diego River, shutting down parts of Mission Beach and Ocean Beach. It made us wonder: How grody is the water that runs through our county?

It turns out it’s not an easy question to answer.

There are 573 bodies of water in San Diego County that are “too polluted or otherwise degraded” to meet water-quality standards, according to data from the state’s Office of Environmental Health Hazard Assessment and the Water Resources Control Board. The biggest clusters of so-called “impaired waters” are in Otay Mesa, Escondido and Pacific Beach.

But those numbers aren’t straightforward either, said Rik Rasmussen, a manager in the State Water Resources Control Board’s water-quality division. Water can be polluted without posing a risk to human health, and the list of impaired water bodies only reflects where researchers have tested samples. Plus, there’s some dispute over what’s natural and what’s pollution.

“The numbers are tricky,” Rasmussen said, “especially when you start looking at the 303d list.”

The 303d list is shorthand for part of the federal Clean Water Act. The law requires states to identify bodies of water that need strict regulation. And the states are supposed to rank them based on how bad the pollution is and how the water is used.

Places where we swim and fish and sneak sips of beer — like Pacific Beach — are often on the list because fecal coliform (translation: poop bacteria) has a habit of getting into the watersheds that connect all of our water bodies.

In 2000, 34 million gallons of sewage ran into the San Diego River — the largest sewage spill in the state’s history — and no one knew it was happening for almost a week.

“Sewer spills are a major issue for the health of the river and the people,” said Rob Hutsel, executive director of the San Diego River Park Foundation.

This week’s spill was much smaller, it’s still a public health concern because so many of San Diego’s homeless live in the canyons around Mission Valley, where the spill started, and they often bathe in the river and drink from it, Hutsel said.

But it doesn’t take a huge sewage spill to land a water body on the list. On San Diego’s rare rainy days, the mounds of dog crap that your neighbor left on the pavement can hitch a ride with the stormwater and make its way into a watershed. So can chemicals that seep out of car washes and industrial plants.

Researchers sometimes call this “urban drool,” and it slides easily across solid surfaces.

Urban drool is a big part of why there are so many impaired waters in Otay Mesa. But the Tijuana Watershed also runs through Otay, and it’s dragging bacteria and toxic waste into the mesa from Baja California.

A map of San Diego’s watersheds drawn by the State Water Resources Control Board

The problem: Tijuana’s population is growing rapidly, but its sanitation system hasn’t kept pace.

“Trash in many cases is being burned in Tijuana,” said Oscar Romo, a UC San Diego professor studies water quality in the Tijuana watershed. And when that happens, hazardous ash gets into the soil and the water.

Couple that with the fact that so many toilets aren’t hooked up to the sewage system in Tijuana, and you have yourself a double whammy.

In Escondido, the impaired waters are linked to Escondido Creek. And it’s one of those places where water-quality monitoring can get even more complicated.

“One of the problems we have here is there’s a lot of listings for selenium,” said Travis Pritchard, a research manager for San Diego Coastkeeper, a nonprofit that keeps tabs on the region’s water quality.

Selenium is a natural byproduct of rock erosion, but it’s also found in manmade products like dandruff shampoo and insect repellant.

If it’s natural, it’s not really pollution. And if it’s not pollution, it doesn’t really need to be regulated.

“Sometimes these city and water board people throw their hands up and say, ‘It’s natural,” Pritchard said. “It’s easier to say it’s natural.”

Either way, selenium is toxic to humans in high doses. So are many other chemicals that find their way into our water.

And that’s why water researchers are working on ways to grade the quality of water and make the data tell the whole story.

Joel Hoffmann

Joel Hoffmann was formerly an investigative reporter for Voice of San Diego, focusing on county government, the San Diego Unified School District and the...

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