Climate change is making polluted sites more susceptible to flooding

The physical and psychological scars from Hurricanes Helene and Milton will take weeks, months and years to repair. The threat from toxic waste released by floodwaters may be felt for decades.

It’s not something people usually think about, but as climate change produces more frequent and intense storms, we need to recognize the damage they do to Superfund sites and large numbers of smaller, unrecognized toxic waste sites. Even when authorities think these sites are under control, flooding can expose people to carcinogens and other dangerous chemicals. 

Flooding from Hurricane Helene impacted a shockingly wide area. Milton brought less flooding, but it cut through the center of Florida. Together, they cut pathways through many of the Superfund sites in the southeast.

These visuals show the hurricanes’ tracks and the current or proposed Superfund sites. 

While rudimentary and not to scale, they give a rough idea of what’s at stake as climate change-induced weather events become more common. What they don’t show is what happens on the ground when flood waters rage through sites where toxic chemicals are buried. 

That is something we know too well here in Houston. When Hurricane Harvey tore through this region in 2017, it exposed a local site named the San Jacinto River Waste Pits Superfund Site to historic water levels. 

The containment areas storing dioxin and other paper mill waste material were breached. Chemicals flowed freely into the river and Galveston Bay, one of the nation’s largest estuaries. Environmental Protection Agency dive teams found dioxin concentrations in the river that were more than 2,000 times higher than the maximum recommended levels.

That is not the only local site threatened by climate change. The Houston area has the most such sites in Texas, and the General Accountability Office estimates that 80 percent of them are at risk. Severe flooding this year put four sites underwater, and that wasn’t even from a hurricane. 

Even as we see more intense rain events, researchers believe sea levels in the Gulf of Mexico at Galveston are rising by more than half an inch a year as Houston experiences the worst subsidence in the country. Taken together, areas that never saw significant flooding in the past are now at risk.

In addition to the challenge that storms pose to known Superfund sites, we share another challenge with communities around the country experiencing increased flooding. 

Houston expanded quickly with the growth of its petrochemical, port and rail industries. Hundreds of smaller industrial sites popped up to service those industries. Over time they moved, merged or closed. No one paid much attention to the chemicals left behind. Homes were built near or on the sites and the businesses were forgotten. 

How many sites are there? A team from Rice University, NYU and Brown went back through the records and identified nearly 2,000 long-gone sites in Houston. With toxic waste contamination, forgotten doesn’t mean gone or safe. Chemicals that seeped into the ground may still be there and may still be deadly. 

Our analysis of known toxic sites in the city identified chemicals that have been linked to more than 30 cancers and other illnesses. 

When flooding hits neighborhoods that never typically flooded in the past, the water mixes with chemicals from old sites, releasing them from the soil. They flow onto streets, lawns and living rooms. The storm runoff becomes a pathway for chemicals to enter waterways and aquifers. 

The people who live closest to the sites are at a higher risk. The study authors estimate that 854,000 Houstonians live within a block of an abandoned site. That’s more than a third of the city’s population potentially at risk from an invisible threat that few are even aware of. The researchers found similar patterns of relic industrial sites in areas increasingly exposed to flooding in every city they looked at. 

The tragic storms that struck the southeast created an immediate need to rebuild damaged homes and shattered lives. But toxic waste creates longer-term health concerns that can take years to manifest.

Our experience here in Houston may be a warning to other communities that we are unprepared for this climate change threat. The EPA recognizes that Superfund sites that were once considered under control may be at risk from climate change, but has been slow to address the threat. 

Looking at the Superfund sites that were inundated in Houston this year, the EPA had inadequate protocols for testing the integrity of the sites following the flooding or notifying the public of the results. 

As a nation, we lack the legislative and regulatory framework to address this evolving pollution problem. If Houston has hundreds of sites, the Texas Coast has thousands and America has millions of locations that will increasingly be inundated by the types of storms that ravaged the Southeast. Environmental laws like the Comprehensive Environmental Response, Compensation and Liability Act, or the Superfund Act, were not created with climate change in mind.  

Finding answers will take time, but based on what we have seen this hurricane season, we need to get started on solutions now.

Jackie Medcalf is the CEO and founder of Texas Health and Environment Alliance, a Houston-based nonprofit that works with communities threatened by Superfund and other historic toxic waste sites.