This action is a revised response to CAA section 126(b) petition from Maryland. In 2016, Maryland submitted a single petition alleging good neighbor violations by 36 electric generating units (EGUs) in five states with respect to the 2008 ozone NAAQS. Also in 2016, Delaware submitted four petitions, each alleging good neighbor violations by individual sources located in Pennsylvania or West Virginia with respect to the 2008 and 2015 ozone NAAQS. EPA previously denied all of the petitions in 2018. Petitioners challenged the denial and on May 19, 2020, the D.C. Circuit remanded EPA’s denial as to four EGUs with selective non-catalytic reductions identified in the Maryland petition. This action addresses the Court’s remand and provides a revised response to the petition.