In the Shadow of Sludge: The Legacy of Coal Waste In Appalachia

What Are Coal Impoundments?

Coal impoundments are large facilities that can hold millions of gallons of waste created from coal mining. Prior to being shipped for production, coal undergoes a "washing" process that separates out the impurities such as silt, dust, fine particles of coal, and water.  This creates a sludge-like waste product—referred to by some as "slurry"—that is pumped into a large, earthen dam called an impoundment.

The Wall Street Journal reported in 2016 that mine waste dams are some of the largest man-made structures on Earth. The graphic below, which accompanied the article, illustrates the basic engineering of these facilities. 

There are some regional variations in how coal impoundments are constructed. For example, coal impoundments on flatter landscapes—such as those in Wyoming—look more like large pits. But impoundments in the mountainous region of Appalachia mostly take the form depicted above. 

As of 2013, there were 601 coal-related impoundments in the U.S., according to data provided by the Mine Safety and Health Administration. 

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