Uncertainty regarding boiler Maximum Available Control Technology (MACT) rules persists after a series of rulings from the Court of Appeals for the District of Columbia. On July 29, 2016, the D.C. Circuit issued an opinion vacating the emissions standards for certain subcategories under the major source rules for industrial, commercial and institutional boilers. (https://www.cadc.uscourts.gov/internet/ opinions.nsf/01A29CE03015718085257FFF0054EFA9/$file/11-1108-1627694.pdf) The D.C. Circuit’s opinion vacated the boiler MACT standards “that would have been affected had the EPA considered all sources included in the subcategories.” EPA subsequently objected to vacature, as it would make the impacted MACT rules unenforceable. EPA then petitioned the D.C. Circuit to reinstate the MACT rules and remand them to EPA for revision.

On December 23, 2016, the D.C. Circuit agreed with EPA, reinstated the boiler MACT rules, and remanded the rules to EPA for revision consistent with its earlier opinion. The D.C. Circuit concluded that “[v] acating the standards at issue here would unnecessarily remove many limitations on emissions of hazardous air pollutants from boilers and allow greater emissions of those pollutants until EPA completes another rulemaking and implements replacement standards.” (https://www.cadc.uscourts.gov/internet/opinions.nsf/ B075443F3591D83D852580920056C5D7/$file/11-1108-1652742.pdf). The remand of the boiler MACT rules gives the Trump administration the opportunity to draft standards more favorable to industry, leaving the rules in effect while EPA decides how to proceed. At the same time, environmental groups continue to pursue litigation against EPA seeking to force the agency to make its restrictions on boiler CO emissions more stringent.