U.S. EPA has sent the White House Office of Management and Budget a set of proposed rules aimed at reducing the amount of mercury and other toxic emissions released by coal-fired power plants.

The high-profile proposal, known as the "Utility MACT" rule, is due by March 16. On Saturday, EPA sent its draft rules to the White House Office of Management and Budget, which is usually the last step before a rule is released.

The utility rules were ordered as a replacement for the Clean Air Mercury Rule (CAMR), a cap-and-trade program for mercury that was created by the George W. Bush administration but was struck down when a federal court decided that the rule violated the Clean Air Act. They are being issued under a section of the Clean Air Act that requires plant-by-plant limits on more than 150 chemicals, including mercury.

Coal plants would be required to install the maximum achievable control technology, or MACT, which is based on the most effective equipment that is being used by existing units. The proposal is expected to be one of the most expensive in recent memory, setting up another clash between EPA and critics of regulation, but experts say the rules will also offer some of the heftiest public health benefits.

Frank O'Donnell, president of the advocacy group Clean Air Watch, said they would have a greater impact than anything else the Obama administration has done on the issue of air pollution.

Toxic pollution is dangerous on its own, but requiring power plants to control those chemicals will also reduce emissions that form soot and smog, he said. The new requirements would cause older coal plants without pollution controls to install the equipment or shut down.

A recent analysis by the North American Electric Reliability Corp. concluded that the requirements could affect 753 coal-fired units and cause up to 15 gigawatts of coal-fired capacity to be retired (E&ENews PM, Oct. 26, 2010).

Most types of toxic pollution can be controlled through well-established equipment, such as scrubbers and baghouses. Mercury controls used to be the exception, but when the George W. Bush administration decided not to set plant-by-plant limits, some states in the Northeast started requiring their power plants to cut their mercury pollution by more than 90 percent.

"Thanks to some state requirements, we are seeing tremendously effective cleanup of mercury and other toxics in the real world," O'Donnell said. "Now it's just a matter of seeing the worst performers brought up to the level of the best performers."

As of last summer, mercury controls had been installed on 169 boilers with a total capacity of more than 60 gigawatts, according to the Institute of Clean Air Companies. Mercury controls have now been installed on units with about 20 percent of the generating capacity of the nation's entire fleet of coal plants.