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Groundwater Beneath Your Feet Is Rising With the Sea. It Could Bring Long-Buried Toxic Contamination With It

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Kristina Hill at the underpass beneath 7th and E 8th streets in Oakland on Jan 11, 2020. The underpass flooded several inches due to King Tides, the highest high tides of the year. These instances offer a window into how and where flooding will happen as sea levels rise.
Kristina Hill at the underpass beneath 7th and East 8th streets in Oakland on Jan 11, 2020. The underpass flooded several inches due to King Tides, the highest high tides of the year. These instances offer a window into how and where flooding will happen as sea levels rise. (Laura Klivans/KQED)

Rising seas can evoke images of waves crashing into beachfront property or a torrent of water rolling through downtown streets. But there’s a lesser-known hazard of climate change for those who live along shorelines the world over: freshwater in the ground beneath them creeping slowly upward.

For many Bay Area residents who live near the water’s edge, little-publicized research indicates the problem could start to manifest in 10-15 years, particularly in low-lying communities like those in Oakland, Alameda and Marin City.

Groundwater rise can cause a host of infrastructure issues like crumbling roads, sewage backups and extended earthquake liquefaction zones. But water that moves silently higher can also have negative impacts on human and ecological health, by resurfacing toxic substances that have lingered for years underground.

“Everything human beings use, they spill,” said Kristina Hill, an associate professor at UC Berkeley’s College of Environmental Design, who researches adapting urban areas and shoreline communities to climate change. The overflow includes “everything we’ve used in the last hundred and fifty years,” Hill said.

And the “everything” she mentions is a lot. The Bay Area is rife with industrial sites, new and old. In East Oakland, industry boomed in the early 1900s, as lumber yards, canneries, rail depots and foundries sprung up. It was a long time before governments enacted any environmental regulations to speak of, starting in the 1960s.

“Through the entire postwar and World War II-era, stuff got dumped informally,” Hill said.

More recent contaminants lie buried as well — chemicals like benzene and toluene, leaked from underground storage tanks. Many toxic sites now considered to be contained could pose a threat as the water ascends.

“Legacy contamination in the soil will be remobilized when the water table comes up and intersects with these areas of contaminated soil,” Hill said.

That contaminated groundwater could seep into a basement or crawlspace beneath a home, or sneak in through a broken sewage line. Some of these chemicals vaporize, so that humans could breathe them in.

The vulnerable groundwater, which lies beneath the surface in a layer of freshwater sitting atop water from the ocean, could affect communities within a mile of the coast, according to a recent report by Silvestrum Climate Associates, detailing the problem in the Bay Area island city of Alameda.

“The relevant thing for the problem is how close [the groundwater] is to the surface,” said Hill. She and her colleagues have analyzed and published data estimating the depth of groundwater in Bay Area coastal communities. They found the water below someone’s backyard is “typically within 6 feet of the surface when you’re within a mile of the bay edge, and so often within 2 feet or 1 foot of the surface,” she said.

If the groundwater flows into contaminants no longer monitored because they are considered contained, those toxic substances may start to move, unnoticed.

Groundwater Rise

“Now it’s possible that you have contamination in that water and you might not see it or smell it. You might not know,” said Alec Naugle, who heads the toxics cleanup division for the San Francisco Bay Regional Water Quality Control Board. The agency regulates the mitigation of contaminated sites in a large area stretching over the nine Bay Area counties.

“If you’re exposed to these chemicals over a lifetime, they can increase your risk of cancer,” Naugle said. “Some of those chemicals also have short-term risks at much higher concentrations that we don’t typically see in the environment.”

Professor Hill and her colleagues have found many locations across the Bay Area at risk. For example, Marin City, she says, has topography like a bowl, and as sea levels rise, it “will fill up with water.”

Many of these neighborhoods have large Black and Latino populations who already deal with unequal environmental health burdens due to living near major freeways and, in Oakland, the port. Residents of East and West Oakland have high rates of asthma, and children in East Oakland are more than twice as likely to suffer from the condition than their peers across Alameda County.

‘How Is That Going to Affect My Family?’

Marquita Price has always called Deep East Oakland, a section of city blocks laid out between two interstates, home. When she was a kid, her extended family spent a lot of time at her grandmother’s lavender house in the Havenscourt neighborhood.

“All of the kids, including myself, would con our parents to be able to all stay and just spend the night with our grandparents, and just sing and dance all night,” she said.

Marquita Price outside her grandmother's house in East Oakland. When she learned about the threat of rising groundwater, her thoughts turned to family health, and their assets like this home.
Marquita Price outside her grandmother’s house in East Oakland. When she learned about the threat of rising groundwater, her thoughts turned to the health of her family and their assets. (Laura Klivans/KQED)

These days, Price is an urban planner for The East Oakland Collective, a nonprofit dedicated to racial and economic equality in the neighborhood.

A few years back, while participating in a design challenge calling for ways the Bay Area could prepare for climate change, Price learned about groundwater rise, and the slow-motion havoc it could wreak on her neighborhood.

She thought immediately of the people and places she loved, such as her grandmother’s home.

“How is that going to affect my family?” Price said, “And my community and the assets that we worked so hard to hold?”

Price then met Hill, the UC Berkeley professor, who has been raising the alarm about the threat of rising groundwater for years. Hill’s work has informed her activism on the issue.

“It’s something that people haven’t really thought of as an impact of sea level rise,” Hill said.

Hill says it’s no coincidence that large numbers of people of color live in low-lying areas that will likely face the threat of rising groundwater first.

“There was either redlining or restrictive homeowner covenants that prevented people of color from moving to neighborhoods on higher ground,” she said. “So effectively, white people … left them to live near the industrial areas and on low ground.”


Regulators Assess Next Moves

Naugle, from the Water Quality Control Board, says contaminated sites are at risk of flooding all along California shorelines.

“There are literally hundreds, perhaps thousands of these cases in our region alone, not to mention statewide,” he said.

He and his team now face the daunting task of assessing which sites are of most concern and what to do about them.

They eventually plan to use a report being written by Silvestrum Climate Associates, the private environmental consulting firm that led the Alameda groundwater study. Over the next few years, Silvestrum staff will map groundwater depths and test for contamination in four Bay Area counties: San Mateo, San Francisco, Marin and Alameda. Naugle and his water board colleagues intend to use the report in identifying the most at-risk locations.

California’s Department of Toxic Substances Control also regulates contaminated sites. Grant Cope, the deputy director for site mitigation and restoration, said the organization plans to tackle the problem as well. He would like to work with the U.S. Geological Survey to overlay maps that show groundwater rise onto maps of contaminated sites, to use as “an early-warning system” for site managers.

What Community Members Can Do

Naugle says if communities are concerned about the management of a site prone to groundwater contamination, they should contact the water board.

“We would take a look at that and figure out if that is something that does need a response,” he said.

Kristina Hill agrees. “Call the regional water board and ask for staff to come to a community meeting,” or call the California Environmental Protection Agency, she said. Community members should ask for updates on the status of cleanup projects in their neighborhoods and whether groundwater is being monitored at its maximum, not average, level.

If not, she said, “Ask for a monitoring well or two to be installed to track maximum groundwater levels nearby,” especially if people live downhill from former industrial sites like dry cleaners, gas stations or factories.

Californians can review sites known to contain contaminants through GeoTracker, an online database where various regulators track cleanup efforts.

Inside homes, Hill said, check seals on plumbing fixtures, like the one on the floor around the toilet, and ask a plumber to check for air leaks that would come from a sewage pipe into your home.

Kris May of Silvestrum Climate Associates lives in a low-lying area in the city of Alameda. She installed a pump in her basement to remove water that collects there, and plans to take a sample to test for specific contaminants. She’s been talking to Alameda city leadership about assembling a network of volunteers to test samples. May also covered her pump with a milk crate, to make sure no humans or pets come in contact with potentially contaminated water.

May cautioned against buying an indoor air monitor to measure toxic contamination that vaporizes from groundwater, called volatile organic compounds, or VOCs. She said they won’t work well for substances like benzene.

Grant Cope of the state’s toxic substances control department, said, “One of the most important things that people can do is to require local governments to pass enforceable standards that apply to groundwater rise due to sea level rise.”

These should include local requirements for new buildings and cleanups.

Include the Community

Earlier this year, Price looked onto a recreation field outside an East Oakland affordable housing development called Coliseum Gardens. The development sits on the location of a former recycling center, ringed by old industrial sites.

The land is low-lying, and the groundwater is close to the surface. Price said people in this area do see some flooding. But awareness was low of “exactly what it is and how contaminated it is and how damaging it really could be.”

As people learn more about the issue and lobby for solutions, Price said, she wants her community to have a role in addressing the problem.

“I don’t want just some outside consultants and companies to come in and carry out the plan,” she said. “Our unemployment is crazy out here. So this could definitely be a low-entry job that can provide to the community and also bring awareness [to the issue] at the same time. We can’t prevent natural disasters or any kind of disasters or problems from happening,” Price said. “It’s just about how we plan for them.”


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