Three months after a massive coal ash spill at a Tennessee utility buried homes and killed scores of fish in over 300 surrounding acres, the feds say they're crafting new rules to ensure coal ash is safely stored.

The Environmental Protection Agency (EPA) sent letters yesterday to 300 electric utilities that have surface impoundments, requesting info on their structural integrity and demanding that damaged units be repaired. “Environmental disasters like the one last December in Kingston should never happen anywhere in this country,” EPA Administrator Lisa Jackson said in a statement. “That is why we are announcing several actions to help us properly protect the families who live near these facilities and the places where they live, work, play and learn.”

Some 129 million tons of coal ash, the residue of coal burning, is produced in the U.S. annually. It is radioactive and contains arsenic, lead and mercury, among other contaminants. While much of it is stored in coal-ash ponds like the Tennessee Valley Authority’s Kingston Fossil power plant in the Watts Bar Reservoir, some environmentalists say it should be put in lined landfills that would stop contaminants from leaching out. Mercury and lead are potent neurotoxins that can cause permanent brain and nervous system damage; arsenic in drinking water has been linked to cancer, atherosclerosis (hardening of the arteries) and nervous system damage.

The December coal-ash spill filled parts of the Emory and Clinch rivers with six feet of sludge, killing fish and flooding homes, causing an estimated $525 million to $825 million in damages.

The agency said its proposed new regs should be ready for public comment by the end of the year.

Image of Kingston Fossil plant coal-ash spill, about 1 mile from retention pond/Brian Stansberry via Wikimedia Commons