A New Source Review (NSR) is a permitting process created by the US Congress in 1977 as part of a series of amendments to the Clean Air Act.
[1] Since the terms "significant increase" and "routine scheduled maintenance" were never precisely defined in legislation, they have become a source of contention in many lawsuits filed by the EPA, public interest groups, and utilities.
WEPCo initially believed that the plant, built in 1932, would not be subject to the NSR requirements and would instead fall under "routine maintenance, repair, and replacement".
However the court did agree with the EPA that the repairs and modifications to the plant did not constitute "routine maintenance" [3] After the WEPCo ruling, the EPA continued to take a case-by-case approach to NSR's at facilities built before 1977, viewing the court's ruling as applying to the power sector specifically and not to all similar NSR applications in general.
Because the changes to the New Source Review substantially weaken the Clean Air Act's ability to prevent pollution and cause many existing enforcement efforts to be dropped, twelve states (New York, Connecticut, Maine, Maryland, Massachusetts, New Hampshire, New Mexico, New Jersey, Pennsylvania, Rhode Island, Vermont, and Wisconsin) and the District of Columbia sued the Bush Administration in October 2003 to block the changes to the New Source Review that are seen as a major rollback of the Clean Air Act and a hazard to public health.