CHATTANOOGA, Tenn. (AP) — The Tennessee Valley Authority’s inspector general says “poor coal ash management practices and management culture” led to TVA’s December 2008 spill on the Emory River in East Tennessee.

The report released Monday on the inspector general’s website describes the spill of sludge laden with selenium, mercury and arsenic as “one of the largest environmental disasters in U.S. history.”

A TVA spokeswoman said they would have to see the report before making any comment.

TVA is fighting damage lawsuits and has released reports that say there is no harm to public health from the 5.4 million cubic yard spill. The inspector general says the ash contains elements “that can be toxic under certain circumstances.”

TVA serves about 9 million people in Tennessee, Alabama, Mississippi, Kentucky, Georgia, North Carolina and Virginia.