On Friday, the D.C. Circuit largely upheld EPA’s Boiler MACT rule.  The industry challenges were a complete washout.  The environmental petitioners won one significant victory and a number of smaller ones.

The environmental petitioners’ one significant victory is important.  EPA included within relevant subcategories any source that burns a fuel containing at least 10% of the “subcategory-defining fuel.”  However, for defining MACT, EPA included only those sources that burn fuel containing at 90% of the subcategory-defining fuel for existing sources, and 100% for new sources.  The Court rejected this approach.

The CAA, however, demands that source subcategories take the bitter with the sweet. Section 7412 mandates, without ambiguity, that the EPA set the MACT floor at the level achieved by the best performing source, or the average of the best performing sources, in a subcategory. It thus follows that if the EPA includes a source in a subcategory, it must take into account that source’s emissions levels in setting the MACT floor.

Which brings me to my big take-away from this decision.  Chevron lives.  By my count, The Court cited Chevron 30 times.  Chevron pervades the decision.  Even in the one big issue that EPA lost, the Court’s decision was based not on a rejection of EPA’s interpretation of an ambiguous provision under step 2 of Chevron, but on a plain meaning interpretation of § 112.  EPA defined what a source is, but it then refused to calculate MACT based upon the performance of all of the sources in a given subcategory.  The statute simply did not allow EPA that leeway.

Other than EPA’s attempt to avoid taking “the bitter with the sweet”, however, the Court’s deference – by three Republican appointees – to EPA’s technical decisions was notable.  Not every case is the Clean Power Plan.  Where EPA is not really pushing the boundaries, I don’t see the Supreme Court weakening Chevron any time soon.