Unveiling a Disguised Climate Threat Endangering U.S. Coastal Communities

By Todd Woody | Bloomberg

Did you know that rising groundwater poses a little-known climate threat? This threat could potentially release toxic chemicals from over 132,000 contaminated sites in coastal areas of the US. In a groundbreaking study, researchers estimated the number of polluted industrial sites and mapped them to areas that are likely to experience groundwater inundation due to rising seas.

“Many people aren’t aware that the ocean actually extends beneath the land in coastal areas. As the ocean rises, it pushes the groundwater up towards the surface,” said Kristina Hill, lead author of the study and an associate professor at the University of California, Berkeley. The findings were published last week in the journal Earth’s Future.

These contaminated sites include factories, fuel stations, military bases, and other industrial facilities that have left the surrounding soil contaminated with cancer-causing chemicals and heavy metals. While some of these sites are managed by the federal government as Superfund sites, the majority are overseen by individual states.

When groundwater rises towards the surface, either due to rising sea levels or increasingly intense storms driven by climate change, the contaminants can leach into the water and spread to other waterways, posing a potential threat to people and wildlife. Chemicals like benzene and trichloroethylene (TCE) can vaporize and enter buildings through cracks in foundations or sewer pipes, further contaminating homes, schools, and businesses.

In 2020, a high school in Oakland had to be temporarily shut down after TCE was discovered in the groundwater beneath the building. The authorities feared that it would vaporize and contaminate the air inside.

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The researchers identified 326 Superfund sites that are vulnerable to rising groundwater in coastal areas. In the San Francisco Bay Area alone, they found over 5,000 state-managed toxic sites near the coast. Extrapolating from their findings, they estimate that there may be more than 132,000 such sites nationwide. The researchers used elevation as an indicator of groundwater levels, identifying contaminated sites located below 10 meters (33 feet) as at risk from flooding. California, New York, and New Hampshire are particularly vulnerable due to the size of their Superfund sites and coastal areas.

By analyzing demographic data, the researchers also found that contaminated areas at risk from rising groundwater are disproportionately located near low-income communities and communities of color.

“These communities deserve to be a priority for full soil remediation,” says Hill, who specializes in studying sea level rise and its impact on urban hydrology.

Jacob Carter, a research director at the Union of Concerned Scientists who has studied the potential impacts of sea level rise on toxic sites, describes the study as significant. He notes that most toxic remediation plans do not take into account the risks posed by sea level rise and other climate change impacts.