The U.S. Environmental Protection Agency says it's working on new regulations that could require coal-fired power plants and chemical companies in South Carolina and elsewhere to set aside money to clean up future toxic waste problems.

Conservation groups hailed the move, saying it closes a loophole and would prevent taxpayers from footing bills for cleanups, especially ones involving coal waste. They said the spill a year ago in Tennessee of a billion gallons of coal ash muck highlighted the need tighter regulations.

A Post and Courier Watchdog report found that many ash ponds and landfills across South Carolina are polluting groundwater with arsenic and other toxic chemicals. Conservation groups fear that taxpayers could some day end up paying to clean up these sites.

While many industries that handle hazardous materials must obtain bonds and other forms of insurance to cover potential toxic waste cleanups, power plants, chemical manufacturers and oil refineries in many cases were excluded from these requirements.

"If EPA succeeds in closing this loophole once and for all, it will force these companies to set aside enough money to clean up the messes they make and encourage them to act more responsibly in the first place," said Lisa Evans of the law firm Earthjustice, which took the EPA to court over the issue.

The EPA said the new rules will reduce taxpayer liability under its Superfund cleanup program.

South Carolina power companies were still assessing the EPA's action. Laura Varn, vice president of corporate communications for Santee Cooper, said she didn't think the rulemaking effort would have an immediate impact.

That could change, however, if the EPA declares coal ash a hazardous waste, she said.

Coal ash currently isn't defined as a hazardous waste under federal rules. The power industry long has opposed the classification, saying it would make it more difficult to recycle coal ash into concrete and other products.

Scott Grigg, public affairs supervisor for SCANA, said that since the EPA has yet to outline any specific regulatory requirements, "there is not a lot of detail to react to." But if coal ash is deemed a hazardous waste, the utility's requirement to set aside funding for potential cleanups "could be significant," he said. "Certainly, whether it's the energy sector or any other industry, increased regulation almost inevitably tends to result in higher costs to consumers."

In separate action, the EPA took preliminary steps to set standards by 2013 or ban four types of toxic chemicals: phthalates, short-chain chlorinated paraffins, polybrominated diphenyl ethers and perfluorinated chemicals.