How Sea Level Rise Poses a Looming Threat to San Leandro's Underground Infrastructure

May 22, 2023

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On an unseasonably hot day on the edge of the San Leandro neighborhood of Mulford Gardens, David O’Donnell uses a heavy metal bar to lift a thick steel cover off a utility hole, exposing an echoey chamber running several hundred feet to the bay.

"Oh, we got a crab in there. It crawled all the way through," said O’Donnell, a maintenance supervisor for the city.

Below ground, tidal water pushes through the city's pipes that were built to pump stormwater in the opposite direction.

"We’re fighting the tide and fighting nature," O’Donnell said. "It's a bit of an uphill battle. There's no pump we can install underground to hold the bay back at high tide."

These pipes — and other below-ground infrastructure — which already periodically flood during high tides could become more routinely inundated as the bay continues to rise because of human-caused climate change.

San Leandro recently secured a small grant to develop a comprehensive plan to address the potential impact rising sea levels could have on its roughly 10-mile shoreline and intricate network of underground pipes. The city is also partnering with a team of San Diego State University climate scientists to determine how many of its 90,000 residents may be at risk from flooding.

"Having the plan now will put us in a much better place to plan how we can move forward into [the future]," said Hoi-Fei Mok, San Leandro's sustainability manager, who uses they/them pronouns.

"It's not like people don't care," said Mok, who grew up in San Leandro, where the vast majority of residents are people of color. "I’m able to tap into what the community is saying and bring that forward to [the San Leandro City Council] and be that extra amplification of community voices."

A former community organizer, Mok says they are dedicated to making sure this community is able to persevere through smoky skies, heat waves, floods and other increasingly frequent climate-induced conditions.

"Ultimately, it is my community that is being impacted," they added.

San Leandro's shoreline makes up less than 3% of the entirety of the lip of San Francisco Bay, but sea level rise will affect this entire region. Mok's work is feeding into a regional partnership to ready every inch of the shoreline for the future.

A Bay Area-wide Regional Shoreline Adaptation Plan is expected to be completed in mid-2024. The team behind it, led by Dana Brechwald, must get buy-in from more than 40 cities and counties — including San Leandro — to engage environmental-justice communities and develop uniform sea level rise standards.

"We want to make sure we’re considering impacts on neighbors so that we don't have this issue of one city behind a tall wall and everybody around it flooding," said Brechwald.

It's still unclear how San Leandro's underground infrastructure will be affected as groundwater rises under the city. Maps produced by the San Francisco Estuary Institute and Pathways Climate Institute show that even 1 foot of sea level rise will cause groundwater to emerge in San Leandro.

The city's stormwater pipes appear to be in good condition, according to Hassan Davani, associate professor at SDSU and a water resources engineer who is leading the team that's partnering with San Leandro. Davani's models don't show major threats in the near term. Still, he said, his work, sponsored by the National Oceanic and Atmospheric Administration, does not include many other underground infrastructures like sewers, belowground power lines and drinking water pipes.

Also, by looking at United States Geological Survey groundwater data, maps of underground infrastructure in the city and middle-of-the-road climate models, Hassan concluded that — as climate change worsens — the current stormwater system will almost certainly "be disrupted" by the end of the century. This could look like the bay pushing further up the drainage system, preventing stormwater from escaping and in turn flooding inland areas of the city.

"We’re going to have flooding further inland, kilometers inland, because the system will be packed with water at the downstream side," he said.

But when taking into account more extreme climate models, Davani said, the disruption to the stormwater system could come around mid-century.

Pauline Russo Cutter, who served as mayor of San Leandro until earlier this year, said the city has also tested its wastewater infrastructure and has yet to find any red flags.

But she recognizes "it's only a matter of time" before emerging groundwater becomes an issue.

"If no one's thinking about it, then these things kind of appear. That's what can sink a city," she said.

In preparing for sea level rise, Mok, the sustainability manager, dreams of a range of solutions — everything from building levees to utilizing marshes to soak up waves.

"I think nature-based solutions have a lot of benefits that I think would be great for us," Mok said.

But, despite the imminent threat that sea level rise poses — with the bay expected to rise by at least a foot in the next three decades — Mok acknowledges that actively preparing for it now can be a hard sell given more immediate concerns like budget issues, staff shortages and ongoing health emergencies.

"Sea level rise is tricky for people to wrap their heads around," said Mok. "I’m hoping this is an opportunity not to get alarmed, but to realize this is something that is coming, not just in San Leandro, but regionally."