John D. Wilson is chair of the Energy and Telecommunications Group and co-chair of the Government and Public Practice Group at the law firm of Michael Best & Friedrich LLP in Madison, Wis. Contact him at 608-283-4433 or jdwilson@michaelbest.com. Brian H. Potts is an environmental and energy law associate in the Madison office of Michael Best & Friedrich LLP. Contact him at 608-257-7470 or bhpotts@michaelbest.com.
The modification rule first was implemented in the 1970 Clean Air Act as part of the new source performance standards (NSPS) program. In Clean Air Act Section 111, Congress directed EPA to create NSPS for various source categories; these NSPS apply the same emission limitations and work-practice procedures to all sources within each specific category. For example, there are NSPS standards for small boilers, large boilers, and coal preparation plants, all of which apply only if the facility was constructed or modified after a certain date. The standards are uniform: All large boilers that are subject to the NSPS must meet the same emission limitations. Because NSPS are not facility specific, however, today most electric facilities only are concerned with the stricter, source-specific requirements known collectively as the New Source Review program.