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On April 21, 2020, the U.S. Court of Appeals for the District of Columbia Circuit issued a 2-1 decision remanding the Environmental Protection Agency's (EPA) 2017 Risk and Technology Review (RTR) of the existing Maximum Achievable Control Technology (MACT) standards for chemical recovery combustion sources at kraft, soda, sulfite and stand-alone semichemical pulp mills (NESHAP Subpart MM). The rule was remanded as the court determined that the Clean Air Act requires EPA to address all regulated hazardous air pollutants (HAPs) (also referred to as “gap filling”) during the RTR rulemaking process. EPA and industry argued that an RTR rulemaking did not implicitly require a review of standards for all HAP pollutants even though EPA acknowledged that this MACT standard would eventually need to be reviewed, at an unspecified future date, to address any previously unaddressed HAPs.

If left standing, this ruling will require EPA to establish emissions limits for previously unregulated HAPs that are known to be emitted from the pulp and paper mill chemical recovery combustion source category in its remand of the RTR rule. This decision has far-reaching implications for other MACT standards that do not have emission limits for all HAPs emitted from a source category. This court ruling, if upheld, does indicate that any future RTR MACT rulemakings would require EPA to “gap fill” the underlying MACT standard during the RTR review process. What is uncertain, beyond the regulatory processes to handle the remand in this case, is how EPA will handle prior RTR final rules and pending RTR rulemakings. This ruling does reinforce that eventually EPA will be required to “gap fill” existing MACT standards although now this requirement would need to occur no later than a particular MACT standard's next RTR.

At the time this article was posted, it remains unclear if EPA will appeal this decision, either by seeking rehearing before the full D.C. Circuit or in the Supreme Court. Regardless, this case is likely to have far reaching implications on a wide range of industries and sources subject to MACT standards that are subject to recent and future RTR reviews.

The full court decision can be found on the U.S. Court of Appeals website.

For more information on this court ruling, contact your local Trinity office at 800.229.6655.