National Parks, Forests and Wilderness Areas are treasured by tens of millions of visitors each year for their scenic vistas and clean air. Degradation of visibility caused by anthropogenic air pollutants at these sites reduces the quality of experience for visitors and also harms the economic interests of cities and industries which rely heavily on tourism income. The Clean Air Act establishes special goals for protection of visibility in many national parks and wilderness areas. Through the 1977 amendments to the Clean Air Act (CAA), Congress set a national goal for visibility as "the prevention of any future, and the remedying of any existing, impairment of visibility in mandatory Class I Federal areas which impairment results from manmade air pollution". The Clean Air Act defines mandatory Class I Federal areas as national parks (over 6000 acres), wilderness areas (over 5000 acres), national memorial parks (over 5000 acres), and international parks that were in existence as of August 1977. The CAA requires that natural visibility conditions be attained in Class I areas by 2064, and also establishes certain requirements for making progress toward attainment at that date. States and tribes have authority under the CAA to develop State and Tribal Implementation Plans (SIPs and TIPs) to attain the CAA visibility standards for these Class I Areas.
The Western Regional Air Partnership (WRAP) has implemented a regional planning process to provide the necessary technical and policy tools needed by states and tribes to comply with the CAA requirements. As part of this effort, the WRAP has established a Regional Modeling Center (RMC) at the University of California, Riverside (UCR) with assistance from ENVIRON Corporation and the University of North Carolina. The WRAP RMC provides assistance to State and Tribal agencies in conducting regional haze analyses over the western United States. This analysis is being performed by operating regional scale, three-dimensional air quality models that simulate the emissions, chemical transformations, and transport of criteria pollutants and fine particulate matter (PM) and consequent effects on visibility in Class I Areas in the western US. A list of all Class I Areas is provided here. The initial phase of this work focused on modeling to support those states which were part of the Grand Canyon Visibility Transport Comission (CGVTC) which have the option to submit an accelerated SIP under Section 309 of the CAA. Beginning in 2003 the focus of this work is shifting toward developing better science and models to be used in Section 308 SIPs and TIPs that will be due beginning in 2007. This website documents the air quality modeling studies used for the WRAP planning process.