Flood Maps Show U.S. Vastly Underestimates Contamination Risk at Old Industrial Sites

Without detailed records, we can’t assess the extent of contamination at each relic site or how that contamination might spread during flooding. But the sheer number of flood-prone sites suggests the U.S. has a widespread problem it will need to solve.

The highest-risk areas tended to be clustered along waterways where industry and worker housing once thrived, areas that often became home to low-income communities.

Legacy of the Industrial Northeast
In Providence, an example of an older industrial city, we found thousands of at-risk relic sites scattered along Narragansett Bay and the floodplains of the Providence and Woonasquatucket Rivers.

Over the decades, as these factories manufactured textiles, machine tools, jewelry and other products, they released untold quantities of environmentally persistent contaminants, including heavy metals like lead and cadmium and volatile organic chemicals, into the surrounding soils and water.

For example, the Rhode Island Department of Health recently reported widespread drinking water contamination from PFAS, often referred to as “forever chemicals,” which are used to create stain- and water-resistant products and can be toxic.

The tendency for older factories to locate close to the water, where they would have easy access to power and transportation, puts these sites at risk today from extreme storms and sea-level rise. Many of these were small factories easily overlooked by regulators.

Chemicals, Oil and Gas
Newer cities, like Houston, are also vulnerable. Houston faces especially high risks given the scale of nearby oil, gas and chemical manufacturing infrastructure and its lack of formal zoning regulations.

In August 2017, historic rains from Hurricane Harvey triggered more than 100 industrial spills in the greater Houston area, releasing more than a half-billion gallons of hazardous chemicals and wastewater into the local environment, including well-known carcinogens such as dioxin, ethylene and PCBs.

Even that event doesn’t reflect the full extent of the industrially polluted lands at growing risk of flooding throughout the city. We found nearly 2,000 relic industrial sites at an elevated risk of flooding in the Houston area; the GAO report raised concerns about only 15.

Many of these properties are concentrated in or near communities of color. In all six cities in our study, we found that the strongest predictor of a neighborhood’s containing a flood-prone site of former hazardous industry is the proportion of nonwhite and non-English-speaking residents.

Keeping Communities Safe
As temperatures rise, air can hold more moisture, leading to strong downpours. Those downpours can trigger flooding, particularly in paved urban areas with less open ground for the water to sink in. Climate change also contributes to sea-level rise, as coastal communities like Annapolis, Maryland, and Miami are discovering with increasing days of high-tide flooding.

Keeping communities safe in a changing climate will mean cleaning up flood-prone industrial relic sites. In some cases, companies can be held financially responsible for the cleanup, but often, the costs fall to taxpayers.

The infrastructure bill that Congress passed in 2021 includes $21 billion for environmental remediation. As a key element of new “green” infrastructure, some of that money could be channeled into flood-prone areas or invested in developing pollution remediation techniques that do not fail when flooded.

Our findings suggest the entire process for prioritizing and cleaning up relic sites needs to be reconsidered to incorporate future flood risk.

Flood and pollution risks are not separate problems. Dealing with them effectively requires deepening relationships with local residents who bear disproportionate risks. If communities are involved from the beginning, the benefits of green redevelopment and mitigation efforts can extend to a much larger population.

One approach suggested by our work is to move beyond individual properties as the basis of environmental hazard and risk assessment and concentrate on affected ecosystems.

Focusing on individual sites misses the historical and geographical scale of industrial pollution. Concentrating remediation on meaningful ecological units, such as watersheds, can create healthier environments with fewer risks when the land floods.

Thomas Marlow is Postdoctoral Fellow in the Center for Interacting Urban Networks (CITIES) at NYU Abu Dhabi, New York University. This articleis published courtesy of The Conversation.