KINGSTON, Tenn. (AP) — The CEO and president of the nation's largest public utility vowed to clean up a community encased in sludge after a major coal ash spill, where many residents fear toxic elements could seep into their drinking water.

Harriman, Tennessee - Millions of yards of ashy sludge broke through a dike at TVA's Kingston coal-fired plant Monday, covering hundreds of acres, knocking one home off its foundation and putting environmentalists on edge about toxic chemicals that may be seeping into the ground and flowing downriver.

In a single year, a coal-fired electric plant deposited more than 2.2 million pounds of toxic materials in a holding pond that failed last week, flooding 300 acres in East Tennessee, according to a 2007 inventory filed with the Environmental Protection Agency.

A wall holding back 80 acres of sludge from a coal plant in central Tennessee broke this week, spilling more than 500 million gallons of waste into the surrounding area.