In October 2000 the floor of a 72-acre wastewater reservoir built above an abandoned mine in Kentucky collapsed, sending black sludge through the mine and out into a tributary of the Big Sandy River.

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Assign each group one of the following rivers on the top 13 list: Missouri River, Canning River, Eel River, Hudson River, Powder River, Mississippi River, Big Sandy River, Snoqualmie River, Animas River, East Fork Lewis, Paine Run, Hackensack River and Catawba River.

CNN: Rivers feel heat as U.S. energy demand rises