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This rulemaking will take final action on two of the three distinct actions included in EPA's February 7, 2019 proposal (84 FR 2670) regarding the National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units (commonly referred to as the Mercury and Air Toxics Standards (MATS)), 40 CFR 63, subpart UUUUU. First, EPA proposed a revised response to the U.S. Supreme Court decision in Michigan v. EPA which held that EPA erred by not considering cost in its determination that regulation of hazardous air pollutant (HAP) emissions from coal- and oil-fired electric utility steam generating units (EGUs) is appropriate and necessary under section 112 of the Clean Air Act (CAA). Second, EPA proposed the results of the residual risk and technology review (RTR) of MATS as required by CAA section 112. [Note: The third distinct action - consideration of a separate acid gas hazardous air pollutant (HAP) emission standard for a subcategory of certain existing EGUs firing eastern bituminous coal refuse - is being addressed in a separate final action; see RIN 2060-AU48.]

Statement of Need:

The EPA completed its review of the Mercury and Air Toxics Standards (MATS) Supplemental Cost Finding (81 FR 24420, April 25, 2016). On February 7, 2019 (84 FR 2670), EPA proposed a revised response to the U.S. Supreme Court decision in Michigan v. EPA, which held that the EPA erred by not considering cost in its determination that regulation of hazardous air pollutant (HAP) emissions from coal- and oil-fired electric utility steam generating units (EGUs) is appropriate and necessary under CAA section 112. After considering the cost of compliance relative to the HAP benefits of regulation, the EPA proposed to find that it is not appropriate and necessary to regulate HAP emissions from coal- and oil-fired EGUs, thereby reversing the Agency’s prior conclusion under CAA section 112(n)(1)(A) and correcting flaws in the Agency’s prior response to Michigan v. EPA. The EPA also proposed that finalizing the new response to Michigan v. EPA will not remove the Coal- and Oil-Fired EGU source category from the CAA section 112(c) list of sources that must be regulated under CAA section 112(d) and will not affect the existing CAA section 112(d) emissions standards that regulate HAP emissions from coal- and oil-fired EGUs. The EPA also proposed the results of the residual risk and technology review (RTR) of MATS that the Agency is required to conduct in accordance with CAA section 112. Based on the results of the reviews, the EPA proposed that no revisions to MATS are warranted. After consideration of public comments, the EPA will issue an action that finalizes decisions and revisions for the rule.

Summary of the Legal Basis:

CAA section 112, 42 U.S.C. 7412, provides the legal framework and basis for regulatory actions addressing emissions of hazardous air pollutants from stationary sources. CAA section 112(f)(2) requires EPA, within 8 years of the promulgation of standards under CAA section 112(d), to determine whether additional standards are needed to provide an ample margin of safety to protect public health or to prevent an adverse environmental effect. CAA section 112(d)(6) requires EPA to review, and revise as necessary, emission standards promulgated under CAA section 112(d) at least every 8 years, taking into account developments in practices, processes, and control technologies.

Alternatives:

In the February 7, 2019 proposal, the EPA solicited comment on two alternative interpretations of the impact of reversing the Supplemental Cost Finding, specifically requesting comment on whether the EPA has the authority or obligation to delist EGUs from CAA section 112(c) and rescind (or to rescind without delisting) MATS. After consideration of public comments, the EPA will issue an action that finalizes decisions and revisions for the rule.

Anticipated Costs and Benefits:

Because the EPA did not propose any amendments to the MATS rule in the February 7, 2019, proposal, there were no cost, environmental, or economic impacts as a result of the proposed action. After consideration of public comments, the EPA will issue an action that finalizes decisions and revisions for the rule. Costs and benefits of the final action will depend on the final decisions and revisions.

Risks:

Based on the results of the residual risk review of the Coal- and Oil-Fired EGU source category, in the February 7, 2019 proposal, the EPA proposed that the residual risks from the source category are acceptable, and the current standards provide an ample margin of safety to protect public health and prevent an adverse environmental effect. After consideration of public comments, the EPA will issue an action that finalizes decisions and revisions for the rule.