This hidden layer of ash, called “slime” by AECOM engineer Bill Walton, was made up of fly ash, water and sediment and, though less than six inches thick, created instability in the pond. As it eluded detection by TVA engineer over the years, its “creep failure” of slimes and liquefaction triggered the massive spill.

These four factors worked together to create what Walton said acted almost like “a perfect storm.” Residents would likely call it a perfect disaster. The massive wave of coal ash that tumbled from the breached pond dumped more than a billion gallons of toxic coal ash on to a neighboring community, knocking homes off their foundation and pouring into the Emory River. Coal ash contains dangers toxins that have been linked to serious health concerns. Already, some residents in the area, including a young child, have tested positive for heavy metals in their blood.

The findings from AECOM will be reviewed by an advisory group made up of personnel from the Tennessee Department of Environment and Conservation, the University of Tennessee, the U.S. Environmental Protection Agency, the U.S. Army Corps of Engineers and geotechnical consultants from Science Applications International Corporation.

Stephen Smith, executive director of the Southern Alliance for Clean Energy, offers this perspective: “One would think that TVA, with its vast engineering experience, would have known to look for this material.”

Sources:
New York Times
Knoxville News Sentinel Co.

SOURCE: Coal Ash Spill › Four factors worked like ‘perfect storm’ to cause coal ash spill