The EPA published a final rule on September 14, 2016 to once
again revise its maximum achievable control technology (MACT)
standard for boilers. In this latest revision, EPA responded to
various requests for reconsideration of its "area source"
boilers rule, the rule that applies only to boilers located at
relatively minor emission sources. The most significant
revision in this latest rulemaking involves changes to the
definitions of "startup" and "shutdown" to
mirror the similar revisions made in EPA's other MACT
rules. That is, the area source boiler rule will now define
startup in two different ways, one of which allows a 4 hour window
during which only work practice standards will apply in lieu of the
otherwise applicable numeric emission limits. EPA also
eliminated the affirmative defense provision for unavoidable
malfunctions, which, until 2014, was the central component of
EPA's policy for addressing emissions resulting from
malfunctions. However, in light
