How Do Sewage Spills Affect Our Health?

Marin's rainy season brings increased risk to our sewage system.

In Marin this rainy season, about three million gallons of raw sewage has spilled into the bay according to the watchdog group SF Baykeeper. Sewage spills, large and small, are common in Marin and storm water runoff is a persistent problem, carrying – unfiltered -- everything from heavy metals to pesticide, animal waste, disease-causing bacteria and garbage into our creek system and on into the bay and ocean.

Another bout of wet weather is expected this week. What do we need to know about the impact of rain on our creek system? How is our health and that of our environment impacted in turn? And what can we do to keep our creeks and ourselves safe and sound?

A sewage spill or runoff is an overflow of untreated or partially-treated sewage

This can include (hold your breath) toxics from Draino to acrylic-covered paint brushes, chronically high levels of disease-causing bacteria such as E. coli and Cryptosporidium, and even a number of viruses, including cholera.

Six years of water quality testing by the nonprofit Friends of Corte Madera Creek Watershed revealed contaminants that exceeded levels recommended for body contact. “Peri Park is foul,” reports Sandy Guldman, president of the Friends of Corte Madera Creek, listing dog and pig fecal bacteria among contaminants there (“which doesn’t surprise you when you see the way people run their dogs”). Larkspur Creek is “really dirty” and has shown bacteria traced to human fecal matter. And San Anselmo “is variable.”

Bacterial levels are volatile and impacted by a lot of different things such as tidal levels and freshwater input, says Guldman, but one thing is uniform: “where the low canal enters the creek all the way to the concrete channel you should not contact the water.”

“What’s in the creek?” asks Director of Marin County Environmental Health Services Rebecca Ng. “What’s on a street? Anything that’s in our environment can get washed into our water bodies,” she emphasizes.

The Corte Madera Creek Watershed is also a significant habitat for fish and migrating birds, all of which are threatened by pollution levels. Find extensive listings of species and learn how you can get involved to protect them here.

How do toxins reach the creek?

"Storm water runoff is the bay’s largest source of pollution by volume,” says Deb Self, Executive Director of SF Baykeeper. “The amount of oil that washes off our city streets is much more consequential than [that of] the Costco Busan Oil spill.”  

As rain falls on city streets, lawns, golf courses, industrial facilities and the like, it picks up all manner of toxic pesticides, bacterial, oil and grease from cars and trash, says Self; and the rain will wash this right into the creek system and bay. In Marin County, as with the rest of the Bay Area except San Francisco, says Self, none of this waste is treated.

“When you flush the toilet or run the washing machine and your lateral (private sewer line) is full, wastewater bubbles out onto the ground,” said Guldman. “Most sewer systems have a little vent; and when they back up this is what happens.”

There is also suspicion, says Guldman, that some people hook private storm drains right to the sewer so it doesn’t erode their yard or property. Though the group hasn’t been able to prove this practice, Guldman reports that “within five minutes of a brisk rain the sewer system is full of water and there is a lot of overflow.”   

When rainwater meets an often archaic sewage system a virtual perfect storm of pollution can result. All homes and business are connected through private lateral lines to a treatment plant – which means that if you are a private homeowner, you own a piece of lateral line, says Self. “These pipes are the same age as your house -- so they can be super old.” 

Then there are all of the city’s pipes, which are also as old as the neighborhoods they course through. Most are sectional clay pipes that nest into each other, explains Self. “They are not solid, and we have a lot of earth movement which can easily lead to breakage.” Add to this pipe-clogging tree roots (especially eucalyptus), along with toilet paper, diapers and “who knows what all heading down pipe” and eventually you then have complete blockage.  

“Then -- here’s the rain connection,” instructs Self, “you have rain water getting into the pipes. It’s supposed to be separate but in reality, we have a lot of rainwater moving through ground and encountering these cracked pipes.” When this large volume of sewage-contaminated rainwater tries to reach the sewage plant but encounters debris, excessive volume builds up and ultimately spews out of a manhole cover, releasing untreated water into the bay.

What can you do to heal the creek and protect your health?

 “Reduce the amount of rainwater that reaches streets and gutters in the first place,” says Self. “Slow it, spread it, sink it,” she says, referring to a phenomenon called the ‘slow water movement.’ There are a number of ways to capture rainwater when it hits, so that gutters don’t empty into the street and rainwater ultimately makes its way into the bay very slowly with a greatly reduced chance of contamination.

One simple way to begin is to clean your laterals, emphasizes Friends of Corte Madera Creek’s Guldman. The Ross Valley Sanitary District offers a grant program that will pay up to $4,000 to homeowners to help them replaces their private lateral pipes.

Baykeeper offers a range of low-impact design techniques, as well as ten tips on how to reduce storm water pollution to the Bay, with such advice as: limit your pesticide and fertilizer use, practice bay-friendly car maintenance, clean up litter and pet feces and help your city to build bay-friendly storm water systems.

Meanwhile, when you and your family participate in your local creek cleanup, says Ng, wash your hands when you're finished.


Friends of the Corte Madera Creek Watershed

San Francisco Baykeeper

10 Tips on how to reduce storm water pollution to the Bay

Publicly-owned wastewater treatment plants in the Bay Area

Low impact development for homeowners

How to clean your lateral lines


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