Barry Thacker, a professional engineer with coal-ash and coal-slurry retention pond design experience, analyzed the Dec. 22 failure of the Tennessee Valley Authority's coal-ash pond on his own time. Thacker concluded high water pressure led to the spill that released 5.4 million cubic yards of toxic sludge into the surrounding area. The consulting firm hired by the TVA concluded the pond failure was due to a layer of "slimes," but an experienced soil scientist backs Thacker's conclusion.

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