The humpbacked levee — steep on one side but gently sloped and thick with willows and tarweed on the other — is a much-discussed sea level rise adaptation project around the Bay Area, especially for wastewater treatment plants. As these plants confront the need to not only stave off flooding of their facilities, but also to upgrade treatment processes to remove nutrients and other pollutants, the living levee, as it has also been called, has become an increasingly viable solution. Read “multi-benefit” project with superpowers: flood protection, habitat, and pollution control all in a hump of dirt and grit with frills.
Seven years into the first demonstration project at San Lorenzo’s Oro Loma Sanitary District, numerous treatment plants around the Bay region are developing their own versions of these wastewater-filtering levees. Indeed how to scale up such wonders was the focus of an afternoon panel at the State of the Estuary conference. As is the case with living shorelines, the region now has solid pilot results from its experiments it now wants to try out at larger sizes in more various situations.
Early experiments at the Oro Loma horizontal levee project showed that passing wastewater through the cells (different mixes of gravel, dirt, water, vegetation) of this highly specialized levee can remove the nutrients that cause harmful algal blooms in the Bay. Further testing suggested the process also works to remove some potentially toxic metals like copper. The latest round of levee experiments, meanwhile, is tackling treatment of the brine, aka reverse osmosis concentrate, from Valley Water’s water recycling and purification plant.
“We tore out a few old cells in the Oro Loma levee and added new ones that included granular activated carbon in a gravel and woodchip mix,” said speaker Anthony DeSalvo from UC Berkeley. In this presentation, he and fellow graduate researcher Jonathan Uhler described how their tweaks to the levee system helped remove even more contaminants from the wastewater. “We saw pretty robust removal of a suite of PFAS,” DeSalvo said. (PFAS are cancer-causing chemicals found in many common products including fire-fighting foams.)
The question really is, can the region build bigger versions of the treatment levee at other sewage plants and then connect them to the Bay? Early indications suggest the wastewater they treat could be clean enough for direct discharge, with various tweaks. The more difficult challenge is the footprint such new levees might have in existing tidal marshes ringing these sewage plants.
Take, for example, the “First Mile Levee Project” proposed along the nearby Hayward Regional Shoreline: the first full-scale demo of the horizontal levee concept. “There’s a pretty well-functioning marsh there today, but we need to add fill to build the new levee and protect the marsh for tomorrow,” said Jackie Zipkin of the East Bay Dischargers Authority in her presentation. As with many innovative shoreline adaptation projects, permitting requirements legislated long before adapting to climate change and sea level rise became an urgent priority are getting in the way. “The regulatory framework isn’t set up to support work that mitigates future conditions, it’s set up to require mitigation for impacts today,” she added.
For the First Mile project, regulators asked Zipkin’s team to consider downsizing the footprint so the marsh was impacted as little as possible, which she found frustrating. Baselines are hard to establish, she says, when you’re comparing habitat today to future habitat lost with no project. Increasing the footprint over time, as sea level rises, is one way to handle it, but then benefits could come too late to prevent flooding. “We’re trying to do a lot with one project,” said Zipkin.
Up in the North Bay engineer Emily Corwin also has a lot of balls in the air with her project: a new treatment wetland planned for the Fairfield-Suisun Sewer District. She prefaced her presentation with the good news: “We have more space to adapt to future conditions than most other sewer plants around the Bay.”
When the District shared their project vision — a combo flood protection levee and wastewater treatment wetland that could also pilot carbon capture techniques — with their neighbors, they got a surprising response. The community asked if the project could include a soccer field, a recreational resource sorely lacking in an area with a high percentage of disadvantaged youth.
In response, Corwin’s team has been struggling to design a hybrid project. While she hopes to include a trail and some open space, managing a soccer field would require help from the local parks department. “Community access pushes the edge of what a sewer district is all about,” says Corwin. “While we want to shift the perception of wastewater treatment from being dirty and dangerous to it being clean and safe, it can get a little smelly around the plant.”
Beyond the community interface, Corwin is laser-focused now on the best size and shape for the levee, the wastewater treatment wetland, and associated carbon capture and peat creation functions (where soil, bacterial processes and decomposing plants bulk up the site in the face of sea level rise). “We want to let nature do the work of building up elevations around our plant,” she says.
The final talk of the panel delved into the engineering and science of what we can do with the concentrate produced by reverse osmosis, better known as Reverse Osmosis Concentrate (ROC). The reverse osmosis process is part of the treatment train at any advanced water purification plant. These plants convert treated wastewater into a highly purified form clean enough for groundwater recharge or potable use.
Recycling more water is a state and local priority in a drought-plagued state. To that end, Valley Water has been operating the Silicon Valley Advanced Water Purification Center in San Jose since 2014 and is planning another South Bay plant for the future. However, this will translate into more ROC that can’t be simply discharged into Bay. The concentrate will require proper management and disposal.
“There are no silver bullets,” said Valley Water’s Medi Sinaki in his talk. Valley Water has been exploring various options: physicochemical and biological breakdown processes; engineered treatment cells; floating wetlands; the horizontal levee; and even dilution with residual effluents of wastewater treatment plants. While the physical and chemical treatment options that have been explored aren’t commercially available right now, or use a lot of energy, according to Sinaki, the nature-based solutions approach where ROC passes through engineered wetlands or horizontal levee systems shows a lot of promise.
The engineered wetlands experiment removed 15-30% of the nutrients and 5-20% of the pharmaceuticals and pesticides from ROC, but failed to remove metals, for example. The new cells at the Oro Loma horizontal levee removed more contaminants and improved other water quality parameters.
“These nature-based solutions pilots show the potential for success for ROC management but need to be 5-6 times bigger to get more reliable data,” said Sinaki.
While the end of the day session filled with science produced some dazed looks in the audience, the take home from the panel came through clear enough. The region’s wastewater treatment plants are stepping up to the challenges ahead, and working with new partners and nature-based approaches in the process. Though perceived as dusty, dirty and smelly, they could be our frontline protection from not only rising seas, but also drought and algal blooms.
Youth vision for the estuary
One other session attended by this reporter stood out in a conference that leaned much more heavily into the people side of a healthy estuary than the usual science. In this session, the SF Estuary Partnership’s Diana Fu asked three members of the next generation to comment on their experiences of the Estuary and the challenges ahead.
When people ask Stockton native Chariz Guerzo where she comes from, a common response is “I’m so sorry.” In fact, when she was growing up in this Central Valley town, parts of which are severely disadvantaged according to EPA rankings, nobody ever told her all the things she could be proud of, for one how Stockton was an early hotbed of labor organizing for farmworkers. “I had to start challenging the narrative that Stockton was a bad place,” she said from her seat on the panel.
Guerzo is now working with Little Manila Rising and Restore the Delta to reduce environmental racism and create more of a green economy. “We’re paying youth to learn about the environment and do water testing,” she says. “Young people should be able to come back to our town and get a job healing the environment rather than working in a warehouse.”
Claire Wong is already doing this work in the South Bay for Grassroots Ecology. This second youth panelist grew up in Hong Kong, where she noticed how devastating the loss of surrounding mangrove ecosystems could be for the city and was inspired to do more. Now she spends her days placing dense mosaics of native plants into transition zones and wetlands.
“Field work is immediately gratifying: you can see, smell, touch the results of your efforts,” she said, adding that the pay is terrible however, even with an environmental degree. “It’s hard to convince high schoolers to choose this profession when there is too little compensation to pay my Bay Area rent,” she said.
“We can’t all be Greta Thunberg,” said Rohan Tyagi from the largely agricultural community of Brentwood, the third youth panelist. Though he’s now a water justice fellow for the Rose Foundation, Tyagi thinks a lot of youth are disconnected from their environment because they don’t have access to greenspace. “It’s hard to put yourself out there, find the access, get involved,” he says. To bridge these barriers he’d like to see more internships and fellowships like his, and also “more intergenerational conversations to help us learn about our environment. Invite youth into your dialogues,” he urged.
Stockton’s Guerzo echoed that sentiment at the end of the session. “Don’t gatekeep from us, educate us about decision-making processes,” she said.
Where There’s an Estuary, There’s a Crowd
More than 700 people attended the 14th biennial State of the Estuary Conference held this past May. The conference provides a forum for collaboration that traces back to the very creation of the San Francisco Estuary Partnership in 1988, a model perhaps of the best kind of government in a time of mounting distrust for public works.
“Our impact can be seen in the volume of state and federal funding going to local projects in the region to maintain a healthy estuary and advance environmental justice, ” says the Partnership’s Caitlin Sweeney.
Local dollars, meanwhile continue flowing from the behind-the-scenes work of the San Francisco Bay Restoration Authority, which wields the will of the region’s residents via a parcel tax in support for wetlands restoration, watershed projects, and other critical nature-based infrastructure. Without these and other partners at the helm of the Bay Area’s efforts to adapt to rising sea levels the region’s shores would soon be underwater. Though that prospect still looms large, at least somebody’s doing something about it.
The KneeDeep Times is a not-for-profit digital magazine reporting on climate resilience and adaptation, with a focus on the San Francisco Bay Area and surrounding regions.