Editors' Summary: EPA's final decision on its proposed WEPCo rule, which addresses how new Clean Air Act provisions apply to electric utilities, is expected soon. This Article provides a glimpse into the regulatory machinery needed to deal with implementing just one aspect of the Clean Air Act Amendments of 1990: whether an electric utility's proposed renovations at one of its facilities constitutes a "modification" triggering new source performance standards and new source review programs. Although Congress passes legislation and the President signs bills into law, executive branch agencies are usually tasked with the regulatory implementation of those laws. Thus, what Congress writes and the President signs into law is often not what interested parties expect. The Article first explores the origins of the controversy, the parties involved, and reaction to EPA's first ruling on the issue. The authors then analyze EPA's response, the proposed WEPCo rule, and evaluate its potential ramifications if made final. Finally, the authors conclude that the proposed rule softens the modification rule as applied to electric utilities in pursuit of utility cost savings, but possibly at the expense of local impacts and technological innovation.