Dirty waves? During the winter the chances are higher. Photo: Pedro Bala
Several times per year, San Francisco’s sewage and stormwater system gets overwhelmed by rain runoff. The excess polluted water flows straight into the Pacific Ocean and San Francisco Bay. The city says it’s the best they can do with their resources, but local environmental groups aren’t satisfied with the efforts.
“When their system is operating properly, it’s a very well-working system,” Sejal Choksi-Chugh, San Francisco Baykeeper executive director, told KQED in a story highlighting the pollution issue. “The problem is when we have heavy rains, their system is not built to hold all those flows. That means the system gets overwhelmed, creating contaminated spots that are harmful for public access.”
“The problem has definitely grown worse,” Choksi-Chugh added. “They’re not allowed to be discharging this much bacteria and pollution into the bay, yet they are doing it.”
The sewage and storm runoff pipes are part of the same system in San Francisco. The city says that the overflow occurs no more than 10 times per year to prevent the streets from flooding. The city has two plants that can hold 200 million gallons of water combined. But, according to a lawsuit filed by the federal Environmental Protection Agency (EPA) and California State Water Resources Control Board in May 2024, the system’s design has discharged 1.8 million gallons of untreated sewage into the ocean since 2016. (It’s worth noting that in late 2024, the Coastal Commission approved a controversial seawall project to protect one of the treatment plants.)
The San Francisco Public Utilities Commission (SFPUC) and the city’s Department of Public Health pull ocean water from 20 sites each week to test water quality. They publish results on their site and specifically mark locations with a flashing red triangle if sewage is being dumped.
Nina Atkind, a local surfer and member of San Francisco’s Surfrider chapter, collects water samples in the city and sends them to a lab to be tested. On the rainy February day when Atkind was corresponding with KQED, she noted that every spot on the map displayed the flashing red triangle that signifies sewage release.
“It’s definitely alarming to see this happen so many times per year, especially on the east side where the water doesn’t move as much as it does on the west side,” said Atkind.
The city says that when the system does overflow, less than 10 percent of the discharged water is “partially treated sewage.”
As far as solutions to the problem, it’s estimated that revamping the entire sewage and floodwater system would have a price tag of $10 billion just on the bay coast of the city – something SFPUC says would require hikes to wastewater bills. Joel Prather, SFPUC’s assistant general manager for wastewater enterprise, discards solutions used by other cities, such as giant tunnels built under Chicago to prevent overflow, stating that the project scope and cost are unrealistic to mimic in San Francisco.
Prather says that 50 years ago the city was releasing 7.6 billion gallons per year, but those discharges have been reduced by 80 percent thanks in part to $2-billion in funding funneled into the issue. The agency’s 10-year capital plan approved in 2023 includes further investment of $4.9 billion for wastewater projects.
However, critics still don’t think it’s enough.
“At this point, I’m not seeing the combined sewer overflow challenge as their highest priority,” David Sedlak, a water quality expert and professor of environmental engineering at UC Berkeley, told KQED. “The real question for San Franciscans and people who enjoy the bay is what are we willing to pay to reduce the number of combined sewer overflows? Is it just the people who live in San Francisco who pay the water and sewer bills there? Or is it something the whole state is interested in taking care of?”
