The U.S. Court of Appeals for the District of Columbia Circuit has agreed to remand an emissions performance standard for certain industrial boilers back to the U.S. EPA so that the agency can review a calculation that was deemed to be flawed.

The EPA in September asked the court for a remand of the boiler Maximum Achievable Control Technology standard, or MACT rule, a request that was supported by the other parties to the case. The D.C. Circuit has now in a Dec. 23 order agreed to send the rule back to the agency for revisions. In several related orders, the court also declined a request to rehear the matter in its entirety, as well as a request to hear the issue before an en banc panel.

The MACT rule set emissions limits on high-emitting boilers and incinerators typically operating at refineries, chemical plants and other industrial facilities while increasing compliance flexibility and dramatically reducing costs. Numerous petitions for review were filed against the MACT standards since they were rolled out in 2011 and the issues were consolidated into one case. The D.C. Circuit opted to hear a challenge to the EPA's decision to exclude certain sources from its calculation of the technology required to meet the emissions standards. This issue was brought forward by a coalition of environmental groups including the Sierra Club.

In August, the D.C. Circuit sided with environmental groups and vacated a portion of the MACT standards, while remanding the remanding portions of the rule back to the agency. The latest order approving EPA's request for remand ties up loose ends in the matter. Judges Karen LeCraft Henderson, Janice Rogers Brown and Thomas Griffith reviewed the rule.

Remanding a rule back to the agency rather than vacating it and setting the agency back to square one to recreate a rule is typical when the defects of a rule are deemed to be curable, the court explained. In this instance, had the rule been vacated in its entirety, the court's opinion is that important limitations on the emission of hazardous air pollutants would have been unnecessarily thrown out.

The court did not impose a deadline on the agency for completing the revisions, but warned that the work must be completed "promptly." If the EPA fails to rework the rule in a reasonable time frame, petitioners are welcome to file another legal challenge.

The case is United States Sugar Corp v. EPA, (No. 11-1108).