After the storm: How San Francisco makes use of rainwater
Last Sunday – San Francisco’s wettest October day on record – a team of seven neighbors was spotted at the intersection of 31st Street and California. Brooms in hand, they tried to sweep rainwater that had flooded the intersection down the street into the gullies.
If they hadn’t come to the rescue, most of the water would have gone there anyway. That’s because, despite some of the most sustainable policies in the country, San Francisco still loses most of its potentially reusable rainwater through runoff.
And that’s a problem. Last week, Governor Gavin Newsom issued a proclamation extending a nationwide drought emergency that gives the State Water Resources Control Board the power to ban wasteful water practices. On Monday after the storms cleared, California’s largest and second largest reservoirs were only 22% and 26% full, respectively. And while about four inches of rain fell on downtown San Francisco last weekend, most of it flowed into the sewers and the ocean.
“As the climate crisis deepens, there is no doubt that increased reuse and reuse of water from all sources, including rainwater when it is available, will be necessary for our survival,” said Supervisor Mandelman, who was particularly vocal on the issue , in a opinion.
Despite the waste of water, San Francisco’s policies are ahead of most other cities in the state. Residents are being reimbursed for rainwater cisterns installed on their property, major construction is required to install water recycling systems, and a rainwater collection project that will irrigate most of a new park in Russian Hill is underway. Since 2012, the SF Public Utilities Commission (PUC) has promoted water recovery by setting up a voluntary program to promote large-scale water reuse systems by setting clear guidelines for developers and water quality standards.
In 2015, Senator Scott Wiener, a city administrator at the time, enacted a law mandating the establishment of these water reuse systems in new settlements over 250,000 square meters. Just last month, a regulation penned by Supervisor Rafael Mandelman expanded that requirement to include new developments of 100,000 square feet or more. Mandelman’s office told the Examiner that legislation “more than doubles” the amount of water reused.
There are different types of rainwater that can be reused with different degrees of filtration and treatment. Gray water is lightly polluted water that was once used and is now considered waste, like water that goes down the drain when you shower or after washing your hands. Rainwater is rainwater that has drained from an area of land or has crossed surfaces such as roads and driveways. Rainwater, the cleanest of these reusable water, comes straight from the sky and at best slips off a non-contaminating surface such as a roof. This water can even become potable with alkaline filtration.
Obtaining rainwater in its simplest form is easy. Water must be channeled through clean gutters or PVC into a storage vessel, such as a cistern. Then that vessel must be connected to a pipeline system with the proper filtration, purification and pressure systems appropriate for the intended use of the water. People who collect rainwater at home usually only need a simple filter screen and hose. Those with green fingers can also use rainwater at home by remodeling gardens to funnel and divert water for irrigation.
“It’s just common sense,” says Laura Allen. She is a founding member of Greywater Action, which educates people about household filter systems, and has also written several manuals on the subject. “People care about the environment, they care about the water, and they see this water flowing down and they know we should make the best use of it, but they don’t always know how.”
In commercial environments, the systems can become more complex but follow the same model. Filter systems often include several stages of treatment and disinfection as well as pressurization so that the water can be used, for example, to flush toilets. Developers and engineers working on these projects must file applications with the PUC, the Department of Public Health, and in some cases, a permit application with the San Francisco Public Works. Application fees and technical reports are also required. In other words, the city’s regulations still come with a fair amount of bureaucracy.
Sherwood Design Engineers, headquartered in San Francisco, is one of the leading West Coast companies that has risen to this challenge. For example, they are restoring the banks and removing retaining walls around Strawberry Creek on the UC Berkeley campus. You are also behind the integrated water management plan for a high-profile, mixed-use community development in San Francisco’s India Basin.
Her renovations in Francisco Park are particularly noteworthy. There, Sherwood Design Engineers have built a world-class rainwater collection system that will hold 500,000 gallons of water and almost completely irrigate the park. In addition to the immense size of the project, it also has a metaphorical value: the park itself was once a huge reservoir from the 1850s that was deserted for almost 80 years. The project reintroduced a useful source of water.
In 2019, large yellow cisterns will be installed to hold rain in Francisco Park, the city’s newest park nearing completion in the Russian Hill area. (Courtesy photo of MCK Americas Inc.)
“At Francisco Park, we actually used a disused drinking water reservoir,” says Amelia Luna, Senior Project Manager at Sherwood. “The city is a leader in the nation promoting and enacting regulations for local reuse of alternative water sources such as rainwater and rainwater,” she added.
But despite all these efforts, one of the most consistent ways to encourage rainwater reuse in San Francisco can be to raise awareness of how to do it at home. In 2005, San Francisco officially legalized the separation of downspouts from the mixed water system to direct rainwater to places like gardens or cisterns. This water can be used, for example, for outdoor irrigation, ornamental fountains and car washes.
“If everyone had even one rain barrel on their buildings, that would be a lot,” says Allen. “It’s about the awareness and the feeling of being connected to our water.”
Greywater Action has dozens of resources for setting up a home irrigation system on their website, and also conducts hands-on workshops and presentations. Additionally, SFPUC customers can be reimbursed up to $ 100 for each of the first two rain barrels on a property, or up to $ 350 for a cistern of up to 5,000 gallons. Interested residents must complete an application on the SFPUC website.
According to the SFPUC, households that collect rainwater can collect 600 gallons of water per 1,000 square feet of roof for every inch of rain. On a day like Sunday, that means the average two or three bedrooms in The City could have accumulated 2,400 gallons – enough for about 240 5-minute showers alone.
virwin@sfexaminer.com
