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Waste Not, Want Less: Tapping Water Supplies from the Drain
By Robin Meadows
When the big rains drenched us in December, my daughter in Palo Alto called me in Fairfield to see if our drought was finally over. You might think she was right — gutters overflowed and streams that had been dry for years were full again — but most of that water just rushed down storm drains and out to sea.
“It’s an amazing lost opportunity,” said Laura Tam, sustainable development policy director of SPUR, a nonprofit dedicated to urban planning in the Bay Area. “We could do a lot more to capture and use stormwater.”
Most tap water in the Bay Area comes from the Sierra Nevada, and lots of rain here doesn’t necessarily mean lots of snow there. Despite Northern California’s heavier than usual rainfall at the end of last year, on January 20, 2015 the Sierra snowpack was still less than a third of normal, according to the California Department of Water Resources. All of California remains in drought and, while you wouldn’t know it from looking at our green hills, the Bay Area is still categorized as being in extreme drought. Wet as December was, it was nowhere near enough to make up for the last three exceptionally dry winters.
But the Bay Area could have collected plenty of water from those welcome storms, if only capture systems were in place. We could harvest more than 50 billion gallons of stormwater per year, or 13 percent of our total urban use, according to the Pacific Institute.
Our cities are designed to shed water quickly via streets, sidewalks, and other hard surfaces that route rainfall into storm drains. Keeping some of that stormwater entails redirecting it through permeable surfaces and into underground basins and cisterns, and San Francisco allows such stormwater capture for non-potable use in commercial, multi-family, and mixed use buildings.
Likewise, the Bay Area is piloting municipal projects that manage stormwater more naturally, allowing it to soak into the ground and recharge groundwater. These include the San Pablo Avenue Green Stormwater Spine, a series of demonstration projects being installed along San Pablo Avenue from Richmond to Oakland. Led by the San Francisco Estuary Partnership in collaboration with Caltrans, the Bay-Friendly Landscaping and Gardening Coalition, and the seven cities along the corridor, these green infrastructure projects are scheduled to wrap up construction by the end of this year.
Approaches include adding grates along sidewalk edges to let water infiltrate the soil, and planting swales to help filter out contaminants such as automotive fluids, heavy metals, and pesticides. “Now, stormwater is running down roads and that filthy water goes into the Bay,” said Elizabeth Dougherty, founder of Wholly H2O, a Bay Area nonprofit dedicated to sustainable water management.
But the city of Los Angeles goes much further than the Bay Area. “LA is a leader in capturing stormwater and using it for their water supply,” Tam said. While San Francisco facilitates stormwater capture for some types of buildings, Los Angeles requires it for groundwater recharge or on-site use in most new development and redevelopment projects.
Also in the works is an ambitious stormwater capture program by the City of Los Angeles Department of Public Works. Called the Greenways to Rivers Arterial Stormwater System, the program repurposes existing corridors — such as wide streets, utility rights-of-way, and stream-side easements — into a stormwater-harvesting network that stretches clear across the vast city. Today, local sources account for just 12 percent of LA’s water use, which averages roughly 187 billion gallons per year. But the city already funnels nearly 8.8 billion per year of stormwater into its aquifers, and plans to boost that to as much as 91 billion per year by the end of the century.
Another underused source of water is wastewater that goes down the drain in houses and office buildings. “Reuse and recycling are the next best ways to create new water supplies,” Tam said. Graywater from showers, bathroom sinks, and washing machines is now the second most common source of water in Australian households, according to the Australian Bureau of Statistics. This wastewater can be reused directly for landscaping and, when treated, can also be reused in washing machines and toilets.
To spur wider use of graywater in the Bay Area, we could follow the lead of Tucson, Arizona, which requires newly constructed homes to be graywater-ready. Dual plumbing collects graywater separately from the blackwater that comes from kitchen sinks, dishwashers, and toilets. “If it makes sense in Tucson, it makes sense in California,” Dougherty said.
Even blackwater can be reused onsite, as long as it is treated properly. The San Francisco Public Utilities Commission’s headquarters building, which opened in 2012, collects and treats both graywater and blackwater with a system that includes plants and bacteria to break down biowaste. The system treats 5,000 gallons of wastewater a day for non-potable reuse, cutting the building’s per person water use by nearly 60 percent.
And, yucky though it may sound at first, all wastewater can be recycled back into drinking water. “In a way, we’re already doing it,” Tam said. “Anybody who’s drinking water from the Delta gets treated wastewater that was deposited upstream.” The Sacramento-San Joaquin Delta, where the Sacramento and San Joaquin rivers meet, supplies about 30 percent of the Bay Area’s water, according to the 2013 San Francisco Bay Area Integrated Regional Water Management Plan (IRWMP).
Last summer, the Santa Clara Valley Water District opened a new treatment plant in San Jose that makes sewer water pure enough to drink. The concept is not new. Orange County has done it for years, but their process includes pumping the water into percolation basins that feed into groundwater. “This adds a margin of safety,” Tam said. “You can test it before sending it out.”
In contrast, the new San Jose plant sends treated wastewater directly out for reuse — and this is not yet legal for drinking water in California. For now, this ultrapure recycled water is used in industrial cooling towers, golf courses, and car washes. But direct potable reuse (DPR) is already happening in the city of Wichita Falls, Texas. Prompted by severe drought, in 2014 the city opened a DPR facility that yields 5 million gallons of water per day, or a third of their demand.
DPR may be coming to California too. As a first step, the State Water Resources Control Board established an expert panel to explore developing regulations for recycling sewer water directly into drinking water. The panel first met last February and is expected to report to the legislature in 2016.
“When the state permits DPR, Santa Clara’s advanced purification facility will be the first,” Tam said. “It’s a leading model for the whole Bay Area.” Today, the Bay Area recycles only about 10 percent of its wastewater, according to the IRWMP. If legalized for drinking water, DPR could meet much more of the Bay Area’s water demand.
“With droughts and climate change, diversifying our water supply is very important,” said Jennifer West, managing director of WateReuse California, a nonprofit that promotes sustainable local water. “We’ll always have our wastewater — it’s drought-proof.”
Robin Meadows (www.robinmeadows.tumblr.com) is the reporting fellow for the 2014-15 Water Education Initiative.
Created by the League of Women Voters of the Bay Area Education Fund to promote better understanding of regional water issues, the initiative is underwritten by the Association of Bay Area Governments, Bay Area Biosolids to Energy, the East Bay Municipal Utility District, the League of Women Voters of Marin County, Louise Anderson, the Marin Municipal Water District, Marion Taylor, the San Francisco Public Utilities Commission, the Santa Clara Valley Water District, and the Sonoma County Water Agency.