First, there is the threat of an impoundment failure. Coal impoundment failures have caused some of the most devastating human and environmental disasters in U.S. history. The most prominent impoundment failure was the Buffalo Creek Disaster in 1972, which killed 125 people in southern West Virginia. The flood left more than 4,000 people without homes.
The West Virginia Department of Culture and History maintains a timeline with archival photos from the disaster.
The second concern with coal waste impoundments is the ongoing threat of slurry leaking into local water sources. While several communities, such as Prenter, W.V., have long presumed that coal waste is impacting their drinking water, there is little definitive research on the subject. A review of 42 water wells in the Big Sandy region of Kentucky and West Virginia found that wells in watersheds near coal impoundments had increased levels of iron—potentially indicating a marker of coal waste contamination. However, scientists noted that it was difficult to separate markers of pollution from naturally occurring metals such as arsenic, manganese, and lead.