Below aging U.S. dams, a potential toxic calamity

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Spokespersons at the Rhode Island dam safety office and the state office responsible for hazardous waste had not considered that a dam failure could flood any of the sites identified by Undark, including Stamina Mills.

By building engineered structures or taking other resiliency measures, the most hazardous waste sites can be designed to withstand flooding, explained Carter, who recently co-authored a report on climate change and coastal flooding hazards to Superfund sites. But in order to prepare for floods, Carter said, flooding hazards have to be recognized first, whether they come from rising seas, increasing storm surge, or, as in these cases, dams.

“They could have looked at that dam and said, ‘Oh, it gets a D minus for infrastructure. This thing could break,’” said Burton, referring to the Edenville Dam. “So in the future, it would be smart of EPA to require the principal party who's responsible for the cleanup to look at the situation to see if it actually could happen.”

One step that could make that process much easier is for dam inundation zones to be regularly included in FEMA’s publicly available flood risk maps, which show the 100-year floodplain and other flood risks to communities, said Ogden. A lack of available data on dam inundations — sometimes the result of security concerns — presents a major obstacle, said a FEMA spokesperson, but plotting inundation zones on commonly-used flood risk maps would ensure communities and agencies are aware of and can respond to dam hazards.

Some states, including Rhode Island, have already made inundation zones, Emergency Action Plans, and inspection reports for the dams they regulate publicly available online. In South Carolina, following a 2015 event when heavy rains caused 50 dams to fail, dam inundations for the most hazardous state-regulated dams were made publicly available. Though no state agency tracks hazardous waste sites within dam inundation zones, Undark was able to identify three dams in South Carolina which could flood a hazardous waste site in the state using this resource.

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