Coal ash, or coal combustion residuals (CCR), is produced whenever coal is burned at coal-fired power plants and is one of the largest forms of industrial waste. While over one-third of coal ash is beneficially reused, often to manufacture cement or wallboard, the rest is disposed of in landfills or surface impoundments. Because coal ash contains many contaminants, including mercury and arsenic, unsafe and unregulated management of coal ash disposal units poses serious environmental and health risks. These risks were realized during a major coal ash spill in Tennessee in 2008 and again in North Carolina in 2014.