EPA Administrator Signs Proposed MATS Rule Revisions

On April 3, 2023, the EPA Administrator signed proposed revisions to Subpart UUUUU of 40 CFR Part 63, commonly known as the Mercury Air Toxics Standards (MATS) Rule.  The signed rule was submitted for publication in the Federal Register.  A copy of the unofficial internet version of the rule preamble is available here.  A redline/strikeout copy of the proposed rule is available here. Comments on the proposed rule must be received on or before sixty (60) days after the date of publication in the Federal Register.  EPA also intends to host a virtual public hearing on fifteen (15) days after publication in the Federal Register.  VIM Technologies (VIM) will post an official copy of this rule notification once it is published in the Federal Register.  A few key proposed revisions are outlined below.

  1. EPA is proposing to require all coal-fired electric generating units (EGUs) to demonstrate compliance with the filterable particulate (PM) limit using PM continuous emission monitoring systems (CEMS).  The alternate quarterly PM stack testing or PM continuous parameter monitoring systems (CPMS) compliance options will be eliminated. EPA notes that there are only four (4) affected units using PM CPMS for MATS compliance.

    EPA is seeking comments on whether EGUs should be able to continue to use quarterly testing past the proposed compliance date for a limited time period or until EGU retirement, whichever occurs first, provided that the EGU is on an enforceable schedule for stopping combustion of coal or oil.

  2. EPA is proposing to change the current filterable PM emission standard for existing coal-fired EGUs from 3.0E-02 lb/MMBtu (or 3.0E-01 lb/MWh) to 1.0E-02 lb/MMBtu (or 1.0E-1 lb/MWh).
  3. For existing lignite-fired EGUs, EPA is proposing to replace the current mercury (Hg) emission standard of 4.0E-06 lb/MMBtu or an alternative output-based emission standard of 4.0E-02 pounds of Hg per gigawatt-hour output (lb/GWh).  The new Hg emission standard would be 1.2 lb/TBtu or an alternative output-based standard of 1.3E-02 lb/GWh.  This is the same standard that existing EGUs combusting other coal types (e.g., subbitumninous, bituminous) must comply with.  EPA is not proposing to change the current Hg emission standard for existing EGUs which do not combust lignite.
  4. EPA is also proposing to remove the option to comply with a total non-Hg hazardous air pollutant (HAP) metals limit or an individual HAP metals limit in lieu of the applicable filterable PM limit.
  5. EPA is proposing to remove “Startup Definition 2”  and notes that less ten (10) EGUs are utilizing this option.  Reference the definition of “Startup” in §63.10042 and Table 3 of the MATS Rule.
  6. EPA is not proposing to revise the current hydrogen chloride (HCl) emission standard (or the alternate sulfur dioxide (SO2) emission standard) for existing coal-fired EGUs.

Please reach out to our COMPAS group at compas@vimtechnologies.com if you’d like a regulatory specialist to discuss the impact these Rule changes have on your system, or our support group at support@vimtechnologies.com to discuss updates to your DAHS in order to comply with the changes.