U.S. EPA expects to propose a replacement rule for the George W. Bush administration's Clean Air Interstate Rule by mid-May, the chairman of the Senate Clean Air Subcommittee said today.

Sen. Tom Carper (D-Del.) said EPA has indicated that it plans to issue the draft rule next month along with a report modeling his multipollutant bill aimed at slashing power plant pollution.

Carper added that he will not mark up his bill in the Environment and Public Works Clean Air Subcommittee until EPA rolls out the draft CAIR bill and its modeling of his legislation.

The bill from Carper and Sen. Lamar Alexander (R-Tenn.) seeks steep cuts in electric utilities' emissions. The measure aims to cut power plants' soot-forming sulfur dioxide (SO2) by 80 percent by 2018, smog-forming nitrogen dioxide (NOx) by 50 percent by 2015 and mercury by 90 percent by 2015.

"Some folks whose pay grade is higher than mine have suggested that maybe the better part of valor here is to let EPA do their work on both of those fronts and then ask Chairman Boxer to hold a markup," Carper said today. "We've made that request, and I think it's been favorably received."

Environment and Public Works Chairwoman Barbara Boxer (D-Calif.) last week said she would schedule a markup "whenever [Carper] has it ready."

EPA officials have said they planned to issue a draft CAIR replacement this month and a final rule in early 2011.

The U.S. Circuit Court of Appeals for the District of Columbia in 2008 struck down the Bush-era cap-and-trade program aimed at cutting NOx and SO2 pollution in the eastern United States. The court temporarily reinstated the CAIR program to give EPA time to craft a replacement.