The majority of the amendments to the Clean Air Act were enacted in 1977 and are known as the Clean Air Amendments of 1977 (P.L. 95-95; 91 Stat. 685). The primary objective of the Clean Air Act is to establish Federal standards for various pollutants from both stationary and mobile sources and to provide for the regulation of polluting emissions via state implementation plans. In addition, the amendments are designed to prevent significant deterioration in certain areas where air quality exceeds national standards, and to provide for improved air quality in areas which do not meet Federal standards ("nonattainment" areas).
Federal facilities are required to comply with air quality standards to the same extent as nongovernmental entities (42 U.S.C. 7418). Part C of the 1977 amendments stipulates requirements to prevent significant deterioration of air quality and, in particular, to preserve air quality in national parks, national wilderness areas, national monuments and national seashores (42 U.S.C. 7470).
The amendments establish Class I, II and III areas, where emissions of particulate matter and sulfur dioxide are to be restricted. The restrictions are most severe in Class I areas and are progressively more lenient in Class II and III areas.
Mandatory Class I Federal lands include all national wilderness areas exceeding 500 acres. Such lands may not be redesignated. (42 U.S.C. 7472) Additionally, national wildlife refuges which exceed 10,000 acres may only be redesignated by States as Class I or Class II areas (42 U.S.C. 7474).
Federal land managers are charged with direct responsibility to protect the air quality and related values (including visibility) of Class I lands and to consider, in consultation with EPA, whether proposed industrial facilities will have an adverse impact on these values (42 U.S.C. 7475(c)). Federal land managers are also required to determine whether existing industrial sources of air pollution must be retrofitted to reduce impacts on Class I areas to acceptable levels.
The Secretary of the Interior, in consultation with other Federal land managers, is required to review all mandatory Class I Federal areas and to identify those where visibility is an important value of the area (42 U.S.C. 7491). Such identifications are to be revised periodically.
EPA is requested to report to Congress regarding methods for achieving greater visibility and to issue regulations towards that objective (42 U.S.C. 7491). Exemptions from such regulations are contingent upon the concurrence of the involved Federal land manager.