On March 30, 1998, the Shasta County, California, Air Quality Management District ("AQMD") issued a federal Clean Air Act prevention of significant deterioration ("PSD") permit to Knauf Fiber Glass, GmbH, authorizing the construction of a new fiberglass manufacturing plant to be located in the City of Shasta Lake, California. Petitions for review of the PSD permit were filed by seventeen private citizens and citizens' groups and by EPA Region IX.