The spill has reignited a debate over whether coal ash should be regulated as a hazardous waste. In 2000, the E.P.A. backed away from its recommendation to do so in the face of industry opposition, promising instead to issue national guidelines for proper ash disposal, though it never did.

I can't identify exactly who is responsible for structural oversight of the retention ponds - the EPA, another federal authority of the state.

Here's a from-the-water view of the disaster:

The fact is that what we're experiencing right now is a top-down disaster. -Paul Krugman