As sea levels rise and torrential rains sweep the land, an invisible threat rises from beneath our feet, groundwater experts say. They urge municipalities to consider the massive infrastructure and public health risks posed by overflowing water tables.
The climate crisis is usually associated with water tables being depleted by extreme heat and drought. But “in some areas, thanks to rising sea levels and more intense rainfall, that water is actually rising higher, bringing with it a wave of problems that few communities are prepared for,” writes Grist.
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“Places in the United States where water tables are getting inch by inch — along the coasts, yes, but also inland, in parts of the Midwest — are already beginning to have infrastructure problems,” the message adds. Old, cracked pipes are flooded, making the pipelines unsuitable for rainwater and waste. “The road is deteriorating faster. Trees drown when the soil becomes more brittle and their roots are deprived of oxygen.”
For poor and low-lying communities, a dangerous concern is that “rising groundwater will mobilize pollutants that have lurked in the ground for years, left behind by industrial and military sites, and allow them to spread unnoticed beneath our feet.”
That threat is now a reality in West Oakland in the San Francisco Bay Area.
“A once thriving black community decimated by racist urban planning practices,” West Oakland has proven over the years to be the home of all manner of toxin-producing industries, from shipyards to smelters to a former military base.
In February 2020, a local high school was forced to close for several weeks after the carcinogenic industrial solvent trichlorethylene (TCE) was discovered in groundwater beneath campus. The source of the TCE was never located, but a local news organization reported at the time that it could be “any or all of five polluting sites within a half-mile radius of the school, including a metalworking shop and a former dry cleaner’s.”
The rise in groundwater is compounding an already acute environmental injustice, said Kristina Hill, a professor at the University of California, Berkeley who studies groundwater rise in urban coastal areas. “Now these areas have both polluted the soil through military or industrial activities, [and] They also have rising groundwater,” Hill said.
Across the country, in low-lying Beaufort County, South Carolina, rising groundwater is threatening septic systems. Just like in West Oakland, sea-level rise is pushing water not just up, but inland, “raising water tables miles from shore,” says Grist. This phenomenon occurs near coasts where the saturated soil below the water table itself sits on salt water from the ocean. “As sea levels rise, groundwater is pushed up because salt water is denser than fresh water,” explains MIT Technology Review.
And that’s not the only way oceans and groundwater are connected, notes Grist.
Daniel Rozell, a Stony Brook University engineer whose 2021 study warned that coastal cities are ignoring the dangers of rising groundwater, said policymakers need to recognize that groundwater is sinking into the sea in an ongoing process called “undersea drainage.” sea shall flow.”
This means that seawalls designed to keep out the rising oceans must also be able to drain groundwater so it doesn’t back up behind the wall and cause the very problems the seawall was designed to prevent.
Septic tank failure is a real threat in places like Beaufort County because the process depends on there being adequate clearance between the septic tank and groundwater. Otherwise, there is no time or space for waste to be filtered off the ground and eaten by bacteria, and raw sewage ends up being washed up into local waterways.
About 20% of US homes depend on sewage systems, and even in offshore areas, groundwater will still rise after climate-related rains.
In some places along Illinois’ Vermilion River, “groundwater seeps into uncased pits that contain coal ash — a hazardous waste — and carry heavy metals into drinking water aquifers,” reports Grist.
Coal ash mines are concentrated in the Midwest and South and are a serious environmental threat. By 2019, the Environmental Integrity Project and Earthjustice had found that more than 90% had contaminated nearby groundwater with heavy metals such as arsenic, cadmium and mercury.
