Now that the Environmental Protection Agency has ended years of delay and pledged to regulate coal ash — the often toxic combustion waste that’s caused damage nationwide — Congressional attention is turning toward other ways to tighten federal oversight of the ash. Of specific interest: the Clean Water Act (CWA), which is the primary law protecting streams, lakes, and wetlands from pollution.

On Thursday morning, the House Transportation and Infrastructure Committee will hold a hearing on coal ash disposal and its effect on water quality. Committee staffers tell Papertrail that lawmakers will examine how the CWA, in particular, might plug longstanding regulatory gaps. Explains Ben Webster, an aide for the Subcommittee on Water Resources and Environment, which called the April 30 hearing, “The absence of [Resource Conservation and Recovery Act] controls has led to a lack of oversight at facilities, which has resulted in pollution from coal ash.”

RCRA is the federal waste law that governs the dumping of hazardous and solid wastes — and the law under which the EPA will propose rules for coal ash. But because ash ponds often leak the ash’s heavy metals into streams, rivers, and wetlands, the CWA represents an alternate regulatory channel. Environmental advocates have complained that the permits issued to power plants to enforce the CWA don’t track many metals associated with coal ash, and have pushed the EPA to update these requirements. Today, the agency’s Office of Water is conducting research on such a prospect.

But the bigger question for environmental groups is just what the EPA’s proposed rule on coal ash disposal will entail. Earlier this week, the Environmental Integrity Project, EarthJustice, and other groups met with agency officials about the status of the rule-making process. By September, according to EPA insiders, the agency plans to have drafted a proposed rule to send to the Office of Management and Budget. Insiders also say the new EPA administrator, Lisa Jackson, hopes to sign the final rule by December, making it ready for possible publication in the Federal Register before January 1.

“Several options are before the administrator and she gets to pick which one because she’s the boss,” says one manager in the Office of Resource Conservation and Recovery, who attended this week’s meeting. The manager says staffers have not shied away from the thorniest political option — regulating coal ash as “hazardous” under RCRA, which would trigger strict controls for its disposal. But they’ve also proposed a “non-hazardous” designation, as well as several hybrids.

“There are multiple decisions to be made,” the manager adds.

Advocates say they’re heartened by what they’ve heard so far. “It seems like they’re leaning toward [hazardous],” says Jeff Stant, of EIP, who lobbied EPA on the issue back in 2000, when it produced a draft determination deeming coal ash “hazardous,” but then backed down after fierce industry lobbying.

Hints of the EPA’s thinking will be on display at tomorrow’s House hearing, it seems. Though the witness list has yet to be released, EPA insiders confirm that Barry Breen, of the Office of Solid Waste and Emergency Response, plans to testify on the agency’s current and future regulatory activities.