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EPA Issues Proposed Rule Announcing Reconsideration of Mercury Air Toxics Standards and Utility NSPS


On November 30, 2012, EPA published proposed rules that reconsider certain aspects of the National Emissions Standards for Hazardous Air Pollutants from Coal-and Oil-Fired Electric Utility Steam Generating Units (known as the Mercury Air Toxic Standards or MATS) and the Standards of Performance for Fossil-Fuel-Fired Electric Utility, Industrial-Commercial-Institutional and Small Industrial-Commercial-Institutional Steam Generating Units (known as the Utility NSPS). The proposed rules are in response to petitions received by EPA for reconsideration of the MATS and Utility NSPS final rules published on February 16, 2012. The reconsideration addresses a limited set of issues: (1) revision of certain MATS new source standards; (2) MATS requirements applicable during periods of start-up and shutdown; (3) Utility NSPS start-up and shutdown provisions related to the particulate matter (PM) standard; and (4) Utility NSPS definition and monitoring provisions.

Of note, EPA has proposed to raise the MATS mercury limit for new electric generating units (EGU) that burn non-low rank virgin coal in response to industry petitions that the limit was too low for emissions to be reliably measured in a manner that would allow sources to operate controls in a way that ensured compliance with the standard. The petitions filed also raised concerns regarding the data and development methods used by EPA in setting certain other MATS emissions standards for new coal-fired sources. As a result, EPA has proposed relaxed standards for filterable PM, hydrogen chloride (HCl), sulfur dioxide limits used as a surrogate for acid gases, lead and selenium for new coal-fired plants. EPA is not proposing any change to the emission standards for existing units under MATS.

Also of note, EPA has proposed clarification of the MATS work practice standards for start-up and shutdown. MATS work practice standards require sources to combust clean fuels during start-up and shutdown. The reconsideration proposal adds certain synthetic natural gas, syngas, propane and ultra-low sulfur diesel to the list of clean fuels. EPA has also proposed to revise the work practice standards to account for the differences in certain types of EGUs for which control devices come online at varying temperatures. EPA has proposed to allow limestone injection to begin after appropriate temperatures have been attained in fluidized bed combustion units and allow control devices to start as soon as technically feasible after the appropriate temperature has been reached. Likewise, EPA has proposed to allow fluidized bed combustion EGU control devices to be disengaged during shutdown, consistent with manufacturers’ specifications. EPA has also proposed revising the definition of start-up to clarify that the start-up period begins with firing of clean fuels and ends with generation of electricity for any useful purpose or production of useful thermal energy, whichever comes first. The definition of shutdown would also be amended to specify that shutdown begins when the EGU no longer generates electricity or makes useful thermal energy or when no coal, liquid oil, syngas, or solid oil-derived fuel is being fired and ends when electricity is no longer generated or the unit no longer makes useful thermal energy and no fuel is being fired.

The comment period for the proposed reconsideration closed on January 7, 2013. EPA has stated it will issue a final reconsideration in March of 2013.

To view a complete PDF of the Fourth Quarter 2012 issue of the Air Quality Letter, click HERE.

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