NACAA Comments on MATS “Appropriate and Necessary” Proposal

April 10, 2019 – NACAA has submitted comments to EPA on the proposed “National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-fired Electric Utility Steam Generating Units – Reconsideration of Supplemental Finding and Residual Risk and Technology Review” (Mercury and Air Toxics Standards – MATS) that was published in the Federal Register on February 7, 2019.  EPA’s proposal would reverse the agency’s previous determination that it is “appropriate and necessary” to regulate emissions of hazardous air pollutants (HAPs) from coal- and oil-fired electricity generating units (EGUs).  It also proposes Risk and Technology Review standards and requests comment on the creation of an additional subcategory for emissions of acid gas HAPs from existing EGUs firing eastern bituminous coal refuse.  NACAA’s letter opposed the elimination or diminishment of the consideration of co-benefits in EPA’s cost benefit analysis of MATS and the agency’s proposal to reverse the appropriate and necessary finding related to the control of HAPs from EGUs.  NACAA identified some deficiencies in the Regulatory Impact Analysis on which EPA based its rulemaking and recommended some improvements.  The association also commented on certain elements of EPA’s risk assessment methodology, including the use of census tract centroids in determining long-term exposures, consideration of facility-wide risks and strategies for evaluating acute exposures.  Finally, NACAA questioned the need for the separate new subcategory identified in the proposal.