Lessons From Elsewhere: Managing San Francisco's Stormwater and Sewage Mess

San Francisco shares one nasty thing in common with New York, Chicago and Milwaukee. When big storms soak each city, millions of gallons of stormwater and raw sewage pour into nearby waterways.

It’s a legacy of how the cities were built over a century ago. Sewage and stormwater flow through the same pipes, and during large storms, the combined systems overflow, spilling into rivers, lakes and oceans. The federal government has mandated that the four cities clean up the water pollution.

San Francisco has spent billions of dollars to improve its system, but it has a long way to go, especially with the growing intensity of storms due to human-caused climate change. Water experts suggest the city can learn from the successes of other cities.

New York has invested in green infrastructure, turning its concrete jungle into a sponge to soak up water. Chicago and Milwaukee both dug massive tunnels deep in the earth to capture water flows while also leading the way with adaptation strategies.

San Francisco has upgraded parts of the combined sewer and stormwater system, installed collection boxes across the city and created hundreds of small green infrastructure projects, all to capture hundreds of millions of gallons of water annually, reducing overflows by 80% since the 1970s.

Most of the year, the system works well, treating all of the city’s wastewater with little issue. However, during the rainy season, the city discharges nearly 2 billion gallons of sewage water into the ocean and San Francisco Bay, according to the Federal Environmental Protection Agency.

Surfers and environmentalists are pressing the city to reduce pollution further and say they avoid the ocean on rainy days because swimming in the murky water can lead to ear and skin infections.

Last winter, sewers spilled into the bay 15 times, according to the San Francisco Public Utilities Commission. In an email to KQED, city officials wrote that all its fixes “alone are not a solution for reducing the impact of the increasingly intense storms that climate change brings.”

The dispute over water pollution in San Francisco reached the Supreme Court after the EPA alleged the city repeatedly violated the Clean Water Act.

San Francisco sued in response, claiming the regulations were too vague. The conservative-leaning court largely sided with the city in an opinion released in early March.

There’s no simple or cheap solution for San Francisco’s sewage woes, and no city has implemented a perfect fix, but Chicago, Milwaukee and New York’s efforts to soak up the rain provide a potential model for how to tackle the problem.

Chicago — ‘Waterways are cleaner than ever’

Chicago has a long history of water quality issues. In the late 1800s, the Chicago River was essentially the city’s latrine and flowed directly into Lake Michigan.

“We soon started to see massive outbreaks of typhoid and other waterborne diseases,” said Karl Rockne, an environmental engineering professor at the University of Illinois Chicago. “We recognized that we had to do something here in Chicago.”

To prevent sewage from reaching Lake Michigan, the city reversed the river’s flow on Jan. 2, 1900. The city later built an elaborate maze of sewers and treatment plants and by 1930, according to the Sewers Collection at the Chicago Library, it had the most extensive system in the world.

But that was not enough, and in the 1970s, the Windy City still discharged sewage into waterways about 100 times a year. The federal government required Chicago to clean up its act.

Since then, Chicago has reduced its smelly water issues by digging massive tunnels up to 300 feet below the Chicago River and others that flow around the city.

The city also captures runoff and sewage in three above-ground reservoirs, storing the water until it can be treated and released. The current system can store 11 billion gallons of water and will have the capacity to hold 17.5 billion gallons by 2029.

“It is working, but there is always going to be some storm that will create problems,” said Marcelo Garcia, professor of civil and environmental engineering at the University of Illinois at Urbana-Champaign. “When the tunnels and reservoirs fill up, and you get another storm that takes you basically back to ground zero.”

Today, the city discharges about 10 times annually, about the same as San Francisco. The Metropolitan Water Reclamation District of Greater Chicago hopes discharges will decrease when the new reservoir is finished.

“The pollution load has drastically decreased,” said Kevin Fitzpatrick, assistant director of engineering for Chicago’s reclamation district. But storms are testing the system, he added, which was designed before the current effects of climate change.

“The waterways are cleaner than ever, but we still have flooding,” Fitzpatrick said. “So we realize [the tunnels and reservoirs] aren’t the only solution.” The agency also manages porous parking lots and hundreds of other projects that allow rainwater to infiltrate into the ground.

What can San Francisco learn from Chicago regarding reducing dirty flows? Garcia said tunnels are an “obvious thing to do,” but it is important to remember that Chicago has many times the open space and can store 16 times more water than San Francisco.

The SFPUC said digging tunnels would significantly raise water bills for San Franciscans. In a fact sheet, the agency wrote the 7-by-7 mile-wide city would need 13 miles of tunnels 24 feet in diameter to capture overflows just on the city’s bayside each year but noted it still wouldn’t prevent discharges “in the biggest storms.”

New York — ‘An all-the-above strategy’

In 2005, the federal government cited New York City for violating the Clean Water Act because its sewer systems spewed contaminated water into Flushing Bay, Jamaica Bay and tributaries to the East River, Long Island Sound and Outer Harbor. Around 60% of New York City’s sewers are part of a combined system.

Unlike Chicago, which sits on massive amounts of limestone that it was able to dig into, New York City has limited subterranean space, extensive underground infrastructure and a high water table.

The Big Apple has instead invested in more than 13,000 rain gardens, green roofs, permeable pavement and other infrastructure projects.

“New York City is not the first city to use green infrastructure, but it is the first city to broadly implement it specifically for this purpose of combined sewer overflow management,” said Bernice Rosenzweig, professor of environmental science at Sarah Lawrence College.

While New York still grapples with reducing its discharges, Rosenzweig thinks San Francisco can learn a lot from it.

“New York City and San Francisco have a lot of similarities,” Rosenzweig said — even though New York’s population is more than 10 times bigger. “They’re some of the densest communities in the United States, and they both rely on subterranean infrastructure.”

Building green infrastructure has the effect of punching “holes” in the hard concrete landscape to “create sponges” so rainwater can be absorbed into the ground, said Jennifer Cherrier, an earth and environmental sciences professor at City University of New York.

The city isn’t relying solely on green infrastructure; it also has plans that include holding tanks, sewer improvements and marsh restoration.

“Our waters are getting a lot cleaner,” Cherrier said. “We have great white shark nursery grounds showing up again. We have had whales underneath the Brooklyn Bridge.”

Still, the advocacy group Save the Sound estimates that more than 21 billion gallons of raw sewage enter New York City’s coastal waters annually, more than 10 times that of San Francisco.

“We really do need an all-of-the-above strategy, and the strategies that are implemented are going to vary across the city,” Rosenzweig said.

Milwaukee — ‘Every drop of water counts’

At the height of a water quality crisis in the 1970s, Milwaukee poured millions of gallons of sewage and stormwater into Lake Michigan an average of 60 times a year. Kevin Shafer, executive director of the Milwaukee Metropolitan Sewerage District, described the rivers in the region “as big, open sewers.”

However, over time, the city brought down the number of discharges; last year, it had only one.

“The goal was zero, and we had one,” Shafer said. “That’s not good enough.”

Milwaukee applied the strategies pioneered in Chicago, digging miles of deep tunnels. It’s also developed more green infrastructure, like New York, transforming more than 5 square miles of land into a watershed and deploying rain barrels and green roofs to capture billions of gallons of water.

“Tunnels are the backbone of everything we do,” he said.

The agency also sends alerts for residents to reduce water use during storms to “preserve the tunnels for the big events by cutting off the water at the surface.”

“When we started it, we were laughed at,” Shafer said. “Now we have people actively signing up.”

The SFPUC said San Francisco’s water use is low compared to other cities, and the city has enough capacity to not issue household alerts. “We’re more worried about the rain coming down rather than people flushing their toilets; we can generally handle that,” said Joel Prather, the SFPUC’s assistant general manager for wastewater enterprise.

While Shafer understands San Francisco is geographically different, he thinks the city could learn from Milwaukee’s success at reducing pollution in Lake Michigan.

“I think you have to take this approach that every drop of water counts, no matter where it hits the surface,” he said.