More than a year after 1 billion or so gallons of water polluted by ash spilled from a coal-burning power plant in Tennessee , the Obama administration is struggling to decide whether to declare such waste "hazardous."

Slapping a hazardous label on coal ash and other coal byproducts would trigger the writing of a federal disposal standard to replace a patchwork of state regulations. The standard could outright ban wet storage ponds — such as the one that ruptured in December 2008 in Kingston, Tenn. — and require landfill liners, leak controls and groundwater monitoring at ash dumps.

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