On December 21, 2011, the United States Environmental Protection Agency ("USEPA") released a final rule setting forth mercury and air toxics standards for power plants (commonly referred to as the "Utility MACT"). The rule applies to electric generating units that are larger than 25 megawatts and burn coal or oil. All existing sources will have at least three years to attain the standards, and state permitting authorities could grant sources an additional year (which EPA expects states typically will grant) as needed for technology installation. EPA also issued an enforcement policy document on December 16, 2011, that provides a procedure for certain units to obtain an additional (fifth) year if necessary to mitigate risks to electric reliability.

Some of the major provisions of the rule include:

• Establishing numerical emission limits for mercury, filterable PM (as a surrogate for toxic non-mercury metals), and HCl (as a surrogate for all toxic acid gases).
• Establishing alternative numeric emission standards, including SO₂ (as an alternate to HCl), individual non-mercury metal air toxics (as an alternate to PM), and total non-mercury metal air toxics (as an alternate to PM) for some power plant subcategories.
• Setting work practice standards, rather than numerical limits, to limit emissions of organic air toxics.
• Revising NSPS standards by setting new numerical emission limits for PM, SO₂, and NOx at fossil-fuel-fired electric generating units.

Some of the major changes from the proposed rule include:

• Establishing work practice standards during startup and shutdown that require units to minimize toxic emissions during these times by burning "clean fuels."
• Establishing a final emission limit for filterable PM as a surrogate for non-mercury metallic air toxics rather than total PM.
• Clarifying coal subcategory definitions to be more specific about which limits apply to which units.
• Revising some new source standards to reflect what emission levels USEPA expects new sources to achieve when they are outfitted with "a full suite of state-of-the-art controls."

Concerns remain within the energy industry that this rule may cause decreased reliability and may force many electric generating units into retirement. The new rule will become effective 60 days after the date of its publication in the Federal Register. More information, including the text of the rule, can be found at http://www.epa.gov/mats.