An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

New Source Review (NSR) Permitting

Final Action Project Aggregation

EPA has completed a reconsideration of a 2009 action to clarify “project aggregation” for the major New Source Review (NSR) permitting program. This action affirms the Agency's 2009 interpretation of when physical or operational changes should be combined into a single “project” for analysis of major NSR applicability. This action also lifts the administrative stay of the 2009 action and explains how the 2009 action applies to states with approved permitting programs. Read a prepublication version of the notice and a summary fact sheet below.

You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.